Stalling / non starting issues when running - Brianmoore!

[Silverfang]

Right, this is an odd one, possible Brianmoore's technical field.

Car starts and runs fine, you can drive it around, but as soon as you've been cruising on the motorway at a steady 70 mph, and pull off and stop a junction, it starts giving problems.

Firstly the rev's will rise sharply to 1800/2000rpm with no throttle input but as soon as you touch the throttle, it dies off completely and stalls out.

After that, the car refuses to start for a couple of minutes, and you have to sit there with the car off before it'll restart, and run perfectly fine.

It'll continue on for a while, and if you're cruising on the motorway, it'll do the same thing again if you come to a halt in traffic or at a junction.

Suspecting the Air flow meter having gone kaput, given the normal operation for most part but then playing up when coming to a halt.

Brianmoore, think you might be able to help in this one.

[Silverfang]

Anyone got any ideas, AFM did not solve this issue, and trying to swap out the ICV, but stumped

[Brianmoooore]

Bit of a weird one, but I'd put the crank sensor high on the the suspect list - heat soak from the engine when it stops being cooled by cold air passing over it.

[Silverfang]

Good call on the Crank sensor Brian

I had a spare that was a working one, swapped it in and the problem so far hasn't reoccurred. Panic over!

To be sure though I am getting a new one via Euros as I'm not too keen relying on an unknown second hand item.

[Silverfang]

Well that was short lived

It's done it again just as i'd got back to my apartment

No idea now.. fuel pump?

[Brianmoooore]

After that, the car refuses to start for a couple of minutes, and you have to sit there with the car off before it'll restart,

You need to find out why this is. No spark? No fuel? Too much fuel?

[TSM3]

I'm having a very similar issue albeit on my M54.
Sitting in traffic will cause it to run rough and bog down. It's also stalled on me a couple of times and won't start unless it's left for a while.

I took it to a dealer last week and they narrowed it down to AFM or throttle position sensor. Codes thrown on the stalls has been crank sensor but guy from the AA didn't think it was the culprit and no codes for that on regular driving. Also not convinved on AFM as unplugging it made no difference (and probably generated the codes BMW see!)

I'm stumped too so interested in what you find.....

May be check throttle position sensor?

[Silverfang]

Ok, I've checked the CPS, resistance came back at 539 ohms, so 570+/-10% means that's in spec.

AFM has been swapped for another working unit already and it did the same again so I can't see it being that.

Throttle position switch I had off last year and gave it a good flush with WD40 to clean out the gunk, but it's been setup correctly though I could check that too.

One thing I did notice this morning when i tried the car this morning before work whilst waiting for a ride, was the fuel pump was rather loud, noticeably louder than the engine at idle...
I did research into pump failures or when fuel pumps are failing, erratic idling (car has done this!) loss of power (Again, has happened) and very noisy (Again, noticed)

I know I probably jumped the gun, but got ahold of a new pump, and pulled the old one out. Found that the old one rattled when shaken side to side, when the new one does not do this... seems suspect to me...

I'll double check the TPS switch though just to be sure, but we'll see

[Silverfang]

Ok.. Fuel pump is now in... but won't run.

Did the jump across the relay and the pump does run, but the relay is not switching... Ideas on a postcard please before i torch this POS

[Brianmoooore]

So the car won't run at all now?
Or will it run with the relay bridged?

[Silverfang]

I've bridged both fuel pump and DME relays, and still won't fire.

There is an old alarm system but that's not worked for years but the car's always ran no issue till now.

I'm completely lost now with this car

[Brianmoooore]

Do you have sparks when the engine turns over?

[Silverfang]

Would this be with the fuel pump and DME bridged?

[Speedtouch]

It doesn't matter; are there any sparks when you crank the engine over?

[Silverfang]

Just checked, yes there is a spark when cranked over with relays replaced back into their slots.

Fuel pump is not running though, but have tried with bridges on both DME and Fuel relay with no start.

Any ideas?

[Speedtouch]

Try using a multimeter or 12V test lamp on the lead to the fuel pump, crank the engine over and see if you're getting 12V.

Or try clouting the pump with a rubber mallet or similar to try to bring it back to life.

[Silverfang]

Did that, and the pump is brand new.
No feed when relay is in place, works when bridged but the car won't fire when cranked over.

[Brianmoooore]

If you have sparks and fuel pressure, then why isn't it running? Probably because the fuel isn't getting into the cylinders.
Check a spark plug tip after cranking to see if it is wet with fuel.

[Speedtouch]

Try a replacement fuel pump relay. Also check Fuse 11:

http://www.e30zone.net/e30zonewiki/index.php/Fuse_Box

[Brianmoooore]

Try a replacement fuel pump relay. Also check Fuse 11:

http://www.e30zone.net/e30zonewiki/index.php/Fuse_Box

If what the OP says is all correct, then you're on the wrong track here. The fuel pump relay won't power up from the ECU, but the pump does run OK when the relay's 'jumped', but the engine still won't start.
He says that the relay doesn't switch by the ECU. ECU should earth one end of the coil, but where does the 12 volt feed for the coil come from?It comes from the same feed that powers the injectors.
See where (I hope) this is going?

[Speedtouch]

You may well be right, but there's no harm in checking the fuse, since there is no mention of it having been checked...

[Silverfang]

Already checked the fuse and continutity check works fine.

Good news, i got it to start up and idle briefly today! However the idle then began to hunt all over the place before it died again and refused to start.
Fuel pump ran lovely and quiet, but was running the whole time before the engine stalled out.

ICV is still suspect and is buzzing very loudly, but at least the ECU isn't broken. Are these affected by heat / age?

I know they can stick and get gummed up with crud but never had one go bad on me before.

I'm going to get a spare from home this weekend (Why i never fitted that one I can't remember why )

[Silverfang]

Just found this article too, and checked the ICV using the method described.. oh surprise surprise. no resistance at all... we have a possible cause now

http://www.pelicanparts.com/bmw/techart ... ooting.htm



Fingers crossed it'll be all running again this weekend.

[Brianmoooore]

ICV might well be responsible for the varying idle, but isn't going to stop the engine from running. Anything the ICV can do can be replicated with the throttle pedal.

[Silverfang]

Just a daft question though Brian:

Does the ECU receive a signal back from the ICV so the ECU knows what position the ICV is in?

I'm only asking as the one on my car is apparently completely shorted out, and if the ECU receives a signal from the ICV, if that's scrambled, then the ECU is not able to compensate, causing the car to stall. Is that possible?

It's cause when i put my foot on the throttle when the idle starts hunting / surging, it stalls out like it's leaning out.

[Grrrmachine]

The ICV is a dumb motor - there's no feedback to the ECU, because the ECU wouldn't be able to do anything anyway. It can't open the throttle because that's a mechanical flap, and it can't do anything other than turn the ICV on. If the ICV is shorted then the engine will die, simple as that.

[Silverfang]

And after a road trip in a Caterham 7 (borrowed from work) ICV has been replaced, and low and behold, after a bit of a difficult start, it fired up, cleared it's throat and lived again.
I've had it up to temp and all seems well again.

[Silverfang]

Or so it seemed... for about 2 days

This POS still is misfiring, loosing all power and generally about as reliable as British Rail aka f'king useless!

Still stumped to what the problem is, but had suggestions of igntion problems cause it stinks of fuel when it's been playing up.

[Speedtouch]

Which ECU do you have? The 0 261 200 380/381 were reknowned for blowing diodes in the idle control circuit.

[Silverfang]

It does have that ECU, and with one of your chips in it Speedtouch.
ONe thing we've noticed now is it stinks of fuel, and misfires a lot, so I'm going to at least test the leads, and put a fresh set of plugs and dizzy cap on it.

[jonny323i]

Iv got several Ecu's that would suit either 380 or 173

[Grrrmachine]

Considering you've changed both the ICV and the CPS, it's probably worth resetting the ECU and letting it re-learn its settings. The instructions you got with your Speedtouch chip should tell you how to do that.

Changing the dizzy cap and rotor is a good idea if you don't know how old they are. Leads, however, should be tested with a multimeter and not just blindly replaced, especially not with aftermarket tat - you want BMW-only leads if you're going to replace them.

Only other thing that might cause a misfire is the DME relay dropping out, but you'd see the rev counter drop to zero when it misfired if that were the case.

[Silverfang]

Well.. got a new dizzy cap and rotor, and have gotten those installed, ... and found 3 broken HT leads

Would explain why it'd not show at idle and when cold... new HT leads now to be ordered.

[Speedtouch]

Aye, that would explain it. Wonder how three came to be broken?

[Silverfang]

No idea, vibration, they weren't all that old at 2-3 years

Either way, would explain a lot