Help me identify the low idle on cold start issue *Problem Found and Fixed*

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HJ1981
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Wed May 15, 2019 6:04 pm

Hey guys,

i have been chasing this issue for a couple of months now. Basically, i replaced the cylinder head gasket and while i was in there, i replaced everything i could find.

All new gauge temperature sensor (brown plug), new DME temperature sensor (blue plug), all new ignition system (new wires incl. sensor, new crank sensor, coil, rotor and plugs), all new cooling system (pump + gasket, thermostat + O-ring, all new OE hoses, radiator, fan clutch etc) new ICV and new TPS, new intake manifold gaskets, valve cover + cylinder head front and rear plugs, exhaust system gaskets and so on.

When i start the car in the morning, i see the rpms sitting at around 600. If i blip the throttle, it hesitate for an instant then revs fine. It does this just once and will never do this again. However, as the rpms drop (after the blimp= the rpms will sink to nearly stalling (300 or so), then come back up to 600 rpms.

When warm, the engine idles at around 700-800, during warm up there is zero hesitation, or any signs of anything wrong (good acceleration, power, throttle response etc).

Here is the thing, one of the previous owners (or someone before me) definitely messed around with the TB stop screw. I see the paint marker on the threads of the screw and the TB housing.

When i followed the Bentley manual (plate adjusted to around 0.005mm) and set the tops (i used a feeler gauge between the TB stop screw and the arm) and set the TPS correctly. The car really struggles when cold start up idle, as if it is coking and no air.

If i were to adjust the stop screw a bit more, and attempt to align the factory paint markings (and adjusting the tps), it idles around 800-900 rpms when cold, but then idles at around 1,000 to 1,200 when warm.

It is as if the DME is getting incorrect readings (tps or blue temp sensor) or the cold rich map is not activated. The sensors are within specs, but i shall pull the DME and check at the pins the values.

Today, i opened up everything short of the intake manifold to double check, everything is nice and tight (hoses, clamps, boot etc). The car is a 1990 E30 325i Swiss spec.

What am i forgetting? following the Bentley manual for the stop screw adjustment (which causes the paint markings to not line up) to have little or no effect.

Tested the ignition system, all is within specs.
Last edited by HJ1981 on Sat May 18, 2019 3:44 pm, edited 1 time in total.
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BenHar
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Wed May 15, 2019 7:17 pm

What engine?

Ben
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HJ1981
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Wed May 15, 2019 7:23 pm

BenHar wrote:
Wed May 15, 2019 7:17 pm
What engine?

Ben
I mentioned it in the end. 1990 325i M20B25.

One more thing, disconnecting the ICV has zero effect on the idle. Yes, tested outside the car and it vibrates. It is as if the DME thinks the car is on part throttle, despite correct TPS install. Unless, i have installed it incorrectly this entire time?
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BenHar
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Wed May 15, 2019 9:59 pm

Sorry, I missed that.

This may help: https://www.e30zone.net/e30wiki/index.p ... ake#Idling

And you could try working though this (although it seems to be impossible to read at the moment):

https://www.e30zone.net/e30wiki/index.p ... oubleshoot

Ben
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HJ1981
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Thu May 16, 2019 7:32 am

BenHar wrote:
Wed May 15, 2019 9:59 pm
Sorry, I missed that.

This may help: https://www.e30zone.net/e30wiki/index.p ... ake#Idling

And you could try working though this (although it seems to be impossible to read at the moment):

https://www.e30zone.net/e30wiki/index.p ... oubleshoot

Ben
Thank you Ben, but i ended up with the conclusion that the DME thinks the throttle is open (or thinks the gas pedal is depressed) constantly. Hence why the ICV is closed, despite the engine condition and the running slightly rich.

So either somehow the TB is mechanically not in working order, or the TPS is installed incorrectly. Thing is, all i did was remove the old TPS, install new one, checked for continuity (beep mode on multimeter) when fully closed (pins 2 and 18) and continuity at WOT (pins 3 and 18). I used finger pressure to turn the TPS anti clockwise till the meter started beeping.

I shall remove the TB and mess around with it, if i can not get it to work correctly, i shall pick up a used TB and compare.
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Thu May 16, 2019 7:53 am

I would first test that all signals are reaching the ecu.

You probably need a helper and a test meter for sure, drop your knee panel - disconnect your battery! and remove the ECU huge plug - pin numbers are marked but tiny!

Blue plug - test at sensor then at ECU ( pin 45 and earth )) for the same resistance reading - about 3K ohms on a warm day of 20 c - 10K ohms at -10 c

Test the TPS switching signals are arriving at the ECU and have continuity ( pins 52 (closed) and 53 (WOT) ) again, between the pins and earth.

Check the ICV for connection to the ECU (pins 4 and 22 ) and has continuity.

It sounds like your ICV is not involved at present, rather as though the idle is being set by the butterfly hold off screw which is nothing to do with idle.

You can "test" the ICV by having the car idle, engage first or better second, then slowly release the clutch ( handbrake off!) the engine should essentially retain its revs as the load increases,
without you touching the throttle at all - this is controled by the ICV, once you push on the gas, the TPS switches and the AFM takes over.

Also you don't say if your injectors are good and clean, rebuilt - but I would think this is not causing your problem.

Oh, I forgot - check carefiully C191 under the inlet manifold, the ICV pin 2 wire goes through this notoriously bad plug/socket to 12v.

Motronic Plug.JPG

Good Luck

Paul :-)
Last edited by paultv on Thu May 16, 2019 4:24 pm, edited 1 time in total.
4th May 1990 325i Convertible.

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HJ1981
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Thu May 16, 2019 10:29 am

paultv wrote:
Thu May 16, 2019 7:53 am
I would first test that all signals are reaching the ecu.

You probably need a helper and a test meter for sure, drop your knee panel - disconnect your battery! and remove the ECU huge plug - pin numbers are marked but tiny!

Blue plug - test at sensor then at ECU ( pin 45 and earth )) for the same resistance reading - about 3K ohms on a warm day of 20 c - 10K ohms at -10 c

Test the TPS switching signals are arriving at the ECU and have continuity ( pins 52 (closed) and 53 (WOT) ) again, between the pins and earth.

Check the ICV for connection to the ECU (pins 4 and 22 ) and has continuity.

It sounds like your ICV is not involved at present, rather as though the idle is being set by the butterfly hold off screw which is nothing to do with idle.

You can "test" the ICV by having the car idle, engage first or better second, then slowly release the clutch ( handbrake off!) the engine should essentially retain its revs as the load increases,
without you touching the throttle at all - this is controled by the ICV, once you push on the gas, the TPS switches and the AFM takes over.

Also you don't say if your injectors are good and clean, rebuilt - but I would think this is not causing your problem.

Oh, I forgot - check carefiully C191 under the inlet manifold, the ICV pin 2 wire goes through this notoriously bad plug/socket to earth - removing the earth would stop the correct operation of the ICV.


Motronic Plug.JPG


Good Luck
Paul :-)
Thank you, i shall be carrying out there tests. My point regarding the idle screw, is maybe it is set to the point that the flap is causing the TPS to think the pedal is being depressed.

I currently have the TB out, and readjusted the screw, was able to "close the flap" a bit more, before adjusting the TPS as per the manual. I shall keep tinkering with the stop screw and the TPS, to the point where adjusting the screw has no effect when adjusting the TPS as well. At this point, i can move on and test the DME signals.

Remember, someone before me has tinkered with that stop screw, and it is a very fine adjustment (0.0381mm/0.0015inch gap according to bentley, which my feeler gauge has a max low of 0.05).

I just checked the C191 harness plug yesterday, no signs of moister or corrosion of any kind, to be safe i sprayed some contact cleaner on both ends, used an air hose to blow it dry and reconnected it, but who knows, i shall be carrying out all DME tests today.

Injectors have been replaced with the updated Bosch ones 0280156346, since i suspected one or more of the older injectors were leaking/clogged (they are out at a Bosch service center getting checked, but it has been weeks since they have arrived, i live in a small town and repairing/ordering parts takes forever).
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paultv
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Thu May 16, 2019 11:01 am

I tried to follow the Bently at one time, but measuring the "gap" is a bit random, as far as I understand it, the screw stops the butterfly from actually coming into contact with the inner circumference of the throttle body - if it does touch, it can jam - so, minimum gap without touching. All the air the engine needs when the throttle is closed comes from the ICV.

Then set the TPS to be "closed" at this point, so that as soon as you open the butterfly, the switch in the TPS operates - you hear the click. Make sure the switch is properly closed when the throttle is shut, and also make sure the throttle cable has the required 2mm or so of slack that BMW recommends - all this helps to make sure the TPS signals that the throttle is closed when it is!

Paul :-)
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HJ1981
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Thu May 16, 2019 11:29 am

paultv wrote:
Thu May 16, 2019 11:01 am
I tried to follow the Bently at one time, but measuring the "gap" is a bit random, as far as I understand it, the screw stops the butterfly from actually coming into contact with the inner circumference of the throttle body - if it does touch, it can jam - so, minimum gap without touching. All the air the engine needs when the throttle is closed comes from the ICV.

Then set the TPS to be "closed" at this point, so that as soon as you open the butterfly, the switch in the TPS operates - you hear the click. Make sure the switch is properly closed when the throttle is shut, and also make sure the throttle cable has the required 2mm or so of slack that BMW recommends - all this helps to make sure the TPS signals that the throttle is closed when it is!

Paul :-)
I believe you are correct regarding your first reply Paul. It does not matter, where the TPS or the stop screw is set at, the car cranks, fires and dies. Sometimes after it fires it sputters then dies. I even backed up the stop screw completely and one could feel the flap binding to the housing when the throttle is opened, also no effect.

The stop screw, set to really open up the flap, is the only way to get the car to idle steadily at all, which means the ICV/DME is NOT controlling the idle as it should be, so something is definitely a miss.

The DME is definitely not getting signals from sensors or to sensors. The car has been sitting overnight and the blue temp sensor shows 2,970 Ohms of resistance (directly on the sensor), it is definitely around 10-15 c coolant temperatures, seems a bit high?

I shall pull the DME plug and check the signals as you suggested in about 1-2 hours. Since it cranks and fires, we can ignore the ignition system? i can probably remove the cap and check for any signs of cracks, same for the rotor maybe (though the whole ignition, fuel and cooling system is new).

I am getting 3 bar fuel pressure at the rail when bypassing the relay (both DME and Fuel pump relays are also new, new fuel filter, pump was replaced by PO).
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paultv
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Thu May 16, 2019 12:37 pm

I would guess as you can get it to run by setting a "fake" idle using the butterfly, everything is fine except the ICV is "out of curcuit" probably a simple crappy connection somewhere - you just need to test all the points I suggest, and don't be diverted by things that are obviously OK - fuel pressure and so on - the blue sensor reading is fine - they vary quite a lot and have a curve from about 500 ohms at about 80 c to 10k ohms at -10 c and its not very linear either -

keep us posted!

Paul :-)
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HJ1981
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Thu May 16, 2019 2:54 pm

So i removed the DME and took reading from the pins.

Blue Temp Sensor (Pin 45 and Pin 2/Ground): 3,244 Ohms
Blue Temp Sensor (At Sensor): 3,244 Ohms

ICV: Tested at Pins 4 and 22 Continuity Present (Multimeter Beep) However the manual indicated it should read 40 Ohms, if this is true where is double check?

TPS: Pin 2 and Pin 52 Continuity Present (Multimeter Beep) on idle, as i start moving the accelerator pedal, No beep/Continuity not present
TPS: Pin 2 and Pin 53 No Continuity (no Beep) on Idle, no Continuity/Beep on half Throttle, Continuity/Beep present on 85%-90% full throttle.

So now i am stumped, looks like something else is the issue. The only things left to check is physically checking the cap and rotor and fuel flow. We have spark, ignition, air, TPS/ICV correct info to PINs, Correct temperature....maybe a clogged fuel filter? but it is new (replaced all fluids and filters 1,000 kms ago).

Anything else to check be it at DME pin or physically? Right now, with correct TPS/Stop screw adjusted, it cranks, fires and dies...sometimes sputters then dies. I did physically remove the AFM and took readings on the flap, i recall resistance changing as i moved the flap and the temp sensor gave me a specific resistance.
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paultv
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Thu May 16, 2019 4:31 pm

Can you check with ignition on you have 12v at pin 2 (centre) of the icv plug and you should have around 40ohms across pins 1 and 3 at the ICV and at the ECU across pins 4 and 22 when the ICV is plugged in - you say you have continuity at the ECU - you mean 0 ohms short circuit?

Does the ICV buzz when ignition is on?

Also to check the cables are good, white/green and white/yellow disconnect the ICV plug and the ECU plug and test across pins 1 and 3 of the ICV plug, this should give open circuit, then using a long piece of lash up wire test each wire for continuity from the ICV plug to the ECU plug.

Also I made an error, C191 is not involved in the power handling for the ICV !! oops

Paul :-)
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HJ1981
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Thu May 16, 2019 5:54 pm

paultv wrote:
Thu May 16, 2019 4:31 pm
Can you check with ignition on you have 12v at pin 2 (centre) of the icv plug and you should have around 40ohms across pins 1 and 3 at the ICV and at the ECU across pins 4 and 22 when the ICV is plugged in - you say you have continuity at the ECU - you mean 0 ohms short circuit?

Does the ICV buzz when ignition is on?

Also to check the cables are good, white/green and white/yellow disconnect the ICV plug and the ECU plug and test across pins 1 and 3 of the ICV plug, this should give open circuit, then using a long piece of lash up wire test each wire for continuity from the ICV plug to the ECU plug.

Also I made an error, C191 is not involved in the power handling for the ICV !! oops

Paul :-)
Will check and report back
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HJ1981
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Thu May 16, 2019 6:57 pm

paultv wrote:
Thu May 16, 2019 4:31 pm
Can you check with ignition on you have 12v at pin 2 (centre) of the icv plug and you should have around 40ohms across pins 1 and 3 at the ICV and at the ECU across pins 4 and 22 when the ICV is plugged in - you say you have continuity at the ECU - you mean 0 ohms short circuit?

Does the ICV buzz when ignition is on?

Also to check the cables are good, white/green and white/yellow disconnect the ICV plug and the ECU plug and test across pins 1 and 3 of the ICV plug, this should give open circuit, then using a long piece of lash up wire test each wire for continuity from the ICV plug to the ECU plug.

Also I made an error, C191 is not involved in the power handling for the ICV !! oops

Paul :-)
Okay, lets start:

12.11v at ICV connector when ignition is on.
43.3 Ohms across Pins 1 and 3 on ICV (the ICV is new) and tested ICV resistance, around 20-22 Ohms between center pin and both outer pins (pin 1 and 2, pins 2 and 3).
ECU Pins 4 and 22 i see 42.9 to 43.1 and it fluctuates between those values.

ICV buzzes and vibrated with ignition on and plugged.

I pulled back the boot on the ICV connector, the white/green and white/yellow look in excellent shape, no tears, touching, exposed, corrosion etc.

Getting a wire long enough to connect the ICV plug to the ECU plug is challenging, can not test that.

I am starting to think, that it maybe a fuelling issue now. Though i see 3 bar when bypassing the relay, maybe the pump is not flowing enough or the faulty voltage.
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paultv
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Fri May 17, 2019 5:58 am

Can you let us know the ECU number, printed on the label -?

There's one I think the 381 that's known to blow ICV control diodes - bit of a long shot.

Paul :-)
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HJ1981
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Fri May 17, 2019 9:27 am

paultv wrote:
Fri May 17, 2019 5:58 am
Can you let us know the ECU number, printed on the label -?

There's one I think the 381 that's known to blow ICV control diodes - bit of a long shot.

Paul :-)
The ECU ends with 173,
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paultv
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Fri May 17, 2019 10:22 am

I see from your first post the ICV is new ( is it real BMW ) - can you see the vane inside move if you take it out of the car and twist it quickly in your hand, can you feel it "clunking" have you washed it out with carb cleaner? maybe it is stuck?

You don't say when this fault first appeared, after the rebuild? or?? and have you driven the car for half an hour to let the ECU re learn everything after having the battery disconnected?

If you pull the ICV hose into the throttle body and block the TB inlet does the fault appear the same - and if you unblock the TB inlet for the ICV - does the engine "race" when you start it?

running out of ideas as well!

Paul :-)
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http://bmwe30cabriolet-wdm.blogspot.de/
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HJ1981
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Fri May 17, 2019 11:49 am

paultv wrote:
Fri May 17, 2019 10:22 am
I see from your first post the ICV is new ( is it real BMW ) - can you see the vane inside move if you take it out of the car and twist it quickly in your hand, can you feel it "clunking" have you washed it out with carb cleaner? maybe it is stuck?

You don't say when this fault first appeared, after the rebuild? or?? and have you driven the car for half an hour to let the ECU re learn everything after having the battery disconnected?

If you pull the ICV hose into the throttle body and block the TB inlet does the fault appear the same - and if you unblock the TB inlet for the ICV - does the engine "race" when you start it?

running out of ideas as well!

Paul :-)
Yes, yes and no. A local German company called Löwe is well known for making brand new (not rebuilt or made in china) ICV, AFMs and other electronic gizmos for older cars. It worked just like stock, even stock ICV has no effect on the car's condition.


The more i think about it, the more i recall the car taking a bit longer to start (fire up) and when it did, the idle would slowly, over the next few days, become more and more erratic and eventually fires up and dies. Hence why i tackled the ICV and TPS first. But it seems more likely a fuel pump issue.

I took the manual and tested everything on the list, except auto transmission and a/c related issues. Everything is within specs, which makes me again point the finger to a mechanical issue (such as pump) since all the inputs to the ECU are correct.
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paultv
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Fri May 17, 2019 2:26 pm

Were you able to test the fuel pressure with engine running?

As you say if the problem slowly appeared it sounds mechanical, but a failing capacitor in the ECU shows errors over time - no one you can swap your ECU with for a
quick test?

I'm driving to Italy tomorrow from Dortmund - where are you?

Paul :-)
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HJ1981
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Fri May 17, 2019 5:50 pm

paultv wrote:
Fri May 17, 2019 2:26 pm
Were you able to test the fuel pressure with engine running?

As you say if the problem slowly appeared it sounds mechanical, but a failing capacitor in the ECU shows errors over time - no one you can swap your ECU with for a
quick test?

I'm driving to Italy tomorrow from Dortmund - where are you?

Paul :-)
No one else in this town has an E30.

I am located in a small city called Passau, but i have ordered some parts already, should be here tomorrow and will be doing further tests. When will you be back in Germany? maybe on the way back we can work something out if the car still refuses to run?
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HJ1981
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Sat May 18, 2019 3:53 pm

Well, i searched around for a good used fuel pump, since i strongly suspect it is the cause despite the correct 3 bar fuel pressure at the rail.

Sadly used pumps are around €50 localls (before shipping), so i searched online for the cheapest possible pump i could find.

I purchased a complete unit excluding the level sensor, costed €22.7 + shipping. I know it would last maybe a week to 10 years, and it is a hit or miss, but it is cheaper to test that new cheap pump than to get an unknown condition used one.

Anyways, i swapped pumps, little to see that the old pump is a Bosch unit and looks great. PO and invoices show the pump and FPR were replaced in 2017 and less than 3.000 kms ago.

I bypassed the fuel pump relay to check leaks, and to my surprised the pump ran quieter and sounded smoother than the old one. Popped the hood and checked the fuel lines, even the sound of the fuel moving inside the lines at the rail sounded very different.

Started the car, she fired and idled at around 900 rpm. Blip the throttle, and steady idle again. No hesitation, no back fire nothing. Drove around till it warmed up, now she idles at 700-800 rpms solid, the engine response is so smooth it is silly. Well, the whole ignition system, cooling system and fuel system (including injectors, ICV and sensors) are brand spanking new.

Fuel economy has increased dramatically for some reason, and the engine is nice and zippy again, especially after 4.000+ rpms it "wakes up".

So, despite the correct and almost instant 3 bar fuel pressure test, the flow was incorrect and since February till now the fuel pump was the issue all along. I shall order a Bosch pump and keep it in the car, till this one dies, since this one is working correctly and surprisingly a 2 year manufacturing warranty (i know, i know i doubt a €22 pump would last this long but just saying).

I definitely have a small vacuum leak somewhere, i suspect the breather tube under the intake, but i shall build a homemade smoke detector and check, as well as check the spark plug gaps again, but my money is on a small vacuum leak somewhere.

What an ordeal this was!
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Fri May 24, 2019 11:28 pm

Well done! :clap:

Good investigative work there fella's!Always turns out to be something simple in the end doesn't it?Well..most of the time at least :mad:

I see what they mean about you covering some miles in your motor PaulTV:

"I'm driving to Italy tomorrow from Dortmund - where are you?" !!! :D
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Sat May 25, 2019 3:58 pm

Hi HJ1981, Where did you get the cheap fuel pump from?
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HJ1981
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Mon May 27, 2019 8:56 am

MunsterScot wrote:
Sat May 25, 2019 3:58 pm
Hi HJ1981, Where did you get the cheap fuel pump from?
if i am allowed to link websites:

https://www.atp-autoteile.de/de

I do have a small misfire on idle, since i used a simple smoke test to check for vacuum leaks, i could not find any. I shall be testing the fuel pressure when the engine is running and d/c the FPR vacuum line and see how the pressure reacts. I suspect the FPR but i am not 100% certain.

I checked the plugs and all 6 are oil free with a nice light brown/light grey colour on them.
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HJ1981
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Mon May 27, 2019 8:58 am

TheWolfman wrote:
Fri May 24, 2019 11:28 pm
Well done! :clap:

Good investigative work there fella's!Always turns out to be something simple in the end doesn't it?Well..most of the time at least :mad:

I see what they mean about you covering some miles in your motor PaulTV:

"I'm driving to Italy tomorrow from Dortmund - where are you?" !!! :D
The pump that came out is a Bosch unit, according to the PO invoices it was replaced in October 2017 and around 3,000 kms ago.

That was why, despite the 3 bar fuel pressure when bypassing the pump, i ruled it out, since i knew it was recently replaced and correct pressure (engine not running) almost immediately.

But after ruling out the sensors, only thing left was the pump.
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paultv
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Mon May 27, 2019 12:20 pm

Glad you sorted it out - what a hassle!!

Paul :-)
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HJ1981
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Mon May 27, 2019 4:50 pm

paultv wrote:
Mon May 27, 2019 12:20 pm
Glad you sorted it out - what a hassle!!

Paul :-)
Thank you paul, but it is not over.

Im trying to figure out that slight idle issue now, just slight one though.

tested the fuel pressure again, bypassed relay, solid 3 bar and 1.000ml flow. So the cheapo pump is still good.

Engine running, i see 2.6 bar (manual indicated 2.8-3.2) and does not increase with engine load/revs. Disconnected the vacuum line and it barely hit 3 bar.

Looks like it maybe slowly dying out?
rix313
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Tue May 28, 2019 2:08 pm

This has been an interesting read for me. I have an issue with my racing car where all of a sudden it started stuttering and being very hesitant under load (I couldn't not get it to stumble while static).

I noticed my gauge was reading 2.6bar when running occasionally fluctuating up to 3bar but I was certain it used to run higher than this. I found when I unplugged the FPR vacuum the pressure went up to 3.3 bar, problem was still there but it happened 75% less. Now I wonder if my pump is also playing up and may be not supplying enough flow although keeping pressure?? I always run my fuel tank very low for weight purposes and also use the main pump to empty the fuel tank so it often runs on very little fuel. Maybe that has broken it.
E30 318iS 'Winston' race car: viewtopic.php?f=88&t=212937

E30 318iS 'Poppy': viewtopic.php?f=25&t=200349

E30 318iS 'Emily': viewtopic.php?f=112&t=277288
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HJ1981
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Thu May 30, 2019 12:50 pm

rix313 wrote:
Tue May 28, 2019 2:08 pm
This has been an interesting read for me. I have an issue with my racing car where all of a sudden it started stuttering and being very hesitant under load (I couldn't not get it to stumble while static).

I noticed my gauge was reading 2.6bar when running occasionally fluctuating up to 3bar but I was certain it used to run higher than this. I found when I unplugged the FPR vacuum the pressure went up to 3.3 bar, problem was still there but it happened 75% less. Now I wonder if my pump is also playing up and may be not supplying enough flow although keeping pressure?? I always run my fuel tank very low for weight purposes and also use the main pump to empty the fuel tank so it often runs on very little fuel. Maybe that has broken it.
After all this, one should test both fuel pump pressure AND flow to isolate the pump from the FPR.

I replaced my FPR, car runs super silky smooth, no flat sports, picks up instantly but still a very slight misfire/rough on idle (warm or cold).

Did several smoke tests, no leaks. Fuel pressure and flow is above spec, ignition system above spec and so on.

Only thing i can think of is a tiny vacuum leak that i can not detect, such as the return tube under the intake maybe (i reused old o-rings). I need to physically remove the cap and check the rotor, but removing that fan and shroud is a PITA. Or maybe even one (or more) of the newer style Bosch injectors are not being "happy" with the engine.
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HJ1981
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Thu May 30, 2019 9:50 pm

Well, i got a new FPR and still see 2.6 bar on idle. No changes when revving up (gets lower as the revs drop) and around 3 bar with the vacuum hose off.

Bypassing the fuel pump relay, i see about 3 bar and flow is above specs (more than 875ml in 30 seconds).

No idea what to do next.
rix313
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Fri May 31, 2019 9:02 am

I've actually got a high flow Walboro pump which I fitted so it was always over spec'd for the job, I am skeptical I have a flow issue as that pump is capable of running double the flow of a standard pump so it would have to be proper fucked if that as the case but I guess it isn't out of the realms of possibility.

Maybe your injectors could do with a service?
E30 318iS 'Winston' race car: viewtopic.php?f=88&t=212937

E30 318iS 'Poppy': viewtopic.php?f=25&t=200349

E30 318iS 'Emily': viewtopic.php?f=112&t=277288
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HJ1981
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Fri May 31, 2019 10:30 am

rix313 wrote:
Fri May 31, 2019 9:02 am
I've actually got a high flow Walboro pump which I fitted so it was always over spec'd for the job, I am skeptical I have a flow issue as that pump is capable of running double the flow of a standard pump so it would have to be proper fucked if that as the case but I guess it isn't out of the realms of possibility.

Maybe your injectors could do with a service?
I have brand new Bosch injectors around 2,000 kms ago installed, they are the newer style ones with 4 hole spray nozzles.

BUT as i experienced with a genuine Bosch fuel pump failing at 2,000 kms, anything is possible. I am sending the original injectors out to get cleaned, tested and resealed by a professional.

I also ordered a Bosch fuel pump to replace that cheap €20 pump, i am not comfortable running such a cheap unit, i only got it for testing anyways.

These intank fuel pumps get really hot, only the surrounding fuel is used to cool them, hence i always fill up at the 1/4 tank mark.

On my previous E82 125i car, it was a known issue that the fuel pump eats itself internally when people run low fuel, it pumps air into the system and causes allsorts of issues.
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HJ1981
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Sun Jun 02, 2019 10:04 pm

Looks like i may have a vacuum leak after all.

brand new Bosch fuel pump and Pierburg 3.0 bar FPR installed. testing the pump (bypassing the relay) i see 3 bar. With the engine running i still see 2.6 bar, disconnecting the FPR vacuum line it goes up to 3.0 bar.

Also when i first started the car, it ran really rough, but i think that maybe "normal" since there could had been some air in the fuel system after installing the new pump.

Still a very slight rough running when warm, but only on idle. partial and WOT car pulls nicely and had no flat spots at all.

I have new intake manifold gaskets and new breather tube (the metal one under the intake) O-rings. Since doing several smoke tests (unpressured honestly, maybe 1-2 psi) revealed no leaks. I shall open up the intake and double check that tube, if there is a leak, it is most likely from there.

The vacuum leak maybe affecting how much the FPR functionality i guess, since it matches intake pressure. 0.2 bar below spec is a lot, must be a big enough leak somewhere.
rix313
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Mon Jun 03, 2019 10:25 am

I back to backed my cars today. Race car pump is 240 LPH which is exactly what it should be. Also my other iS runs at around 2.6 bar fuel pressure also. So I'll have to keep looking.
E30 318iS 'Winston' race car: viewtopic.php?f=88&t=212937

E30 318iS 'Poppy': viewtopic.php?f=25&t=200349

E30 318iS 'Emily': viewtopic.php?f=112&t=277288
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paultv
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Mon Jun 03, 2019 12:25 pm

Have you checked little things such as the oil filler cap seal and the oil dipstick seal - both severely affect the idle as well as the distributor cap contacts and rotor -
I clean mine up everything 3000km or so, this also has massive effect on smooth idle and engine livelyness.


Paul :-)
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http://bmwe30cabriolet-wdm.blogspot.de/
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