E30 Zone

Well, got my own problems this morning. Drove the wife's LPG 325 touring yesterday, and could feel a slight misfire at idle and an increased idle speed.
Put the laptop on the gas ECU yesterday, and the readings were way off. No doubt caused by unburnt fuel getting to the lambda sensor and seriously upsetting the gas ECU.
Started pulling plug leads to try to find which cylinder was down, but found I couldn't really hear much difference untill I got down to just two leads on.
That showed it was No1 that wasn't contributing, but still ran on for several seconds with just one plug lead on!
Now I've got to go and find out what's up.

I had a problem with a range rover that I had LPG on, and the spark wasnt strong enough to ignite the gas properly, so I changed the coil and put a set of expensive silicone leads on and it never missed a beat after that.
Another thing to investigate is the compression on each cylinder, with gas it burns hotter and drier than petrol so can cause premature valve seat wear leading to low compression and slight uneven running, Jeep v8's suffer alot from this. There are upper cylinder lubrication systems available now.
Good Luck.

Nan, it won't be anything to do with LPG. BMW valves, leads and valve seats are a bit better quality than Range Rover. It'll just be a rotor arm or plug.
Still haven't done anything though. Been sidetracked by people turning up here, and now it's GP time.

Right, after working on this (five minute) problem for all of yesterday and most of today, I've finaly run it to ground.
Misfire was present on petrol and LPG, so, since the two fuel systems are completely independant, I thought it must be an ignition problem.
Took off distributor cap and rotor. No obvious problem, but looking a bit ropey, so thet were both replaced.
Leads were all tested as well while they were off, and all checked OK.
Fired the engine up - still the same.
Changed the plugs - no difference.
Changed the leads, and the crank position sensor, while I was at it.
Found a nice piece of bare oil pressure switch wire behind the water pump, just waiting to give me heart failure one day, by turning on the oil pressure light at some inopurtune moment.
Unfortunately, missfire still there.
So now, most of the ignition has been replaced, and still no better.
Decide that maybe the petrol missfire, is being caused by gummed injectors ( they're only used for the first start of the day. The rest of the time they just sit there under pressure, presumably weeping very slowly and gumming up. If I do have to run on petrol, it can take several miles for the car to run properly, and the LPG missfire is being caused by a fault in that system.
Next step was to replace the lambda probe - twice, as the first one I tried was an unknown quantity anyway.
No improvement.
Find out that the LPG tank has only just been filled, and am now wondering if I've bought a tank of poor quality gas.
Hooked the laptop up to the gas ECU, and went for a 20 mile drive.
Laptop display showed that under hard acceleration the car was fueling almost normally, was cutting off properly on over run, but on constant light throttle, such as following traffic slightly uphill at 50 MPH, the mixture would go lean, with no output from the lambda sensor, and the gas valve opening right up to it's limit, then the ECU would show a fault code - mixture lean for too long.
Bedtime, a night's sleep, and inspiration.
All the above has the syptoms of an air leak into the inlet manifold but I certainly couldn't hear any trace of one.
Removed air filter and air meter to get some room, and fired the engine up on petrol.
2m length of hosepipe, one end in ear ,other probing around under the inlet manifold. Sounded like slight air hissing to the left of No 1 gasket, but I thought this also could have been the sound of water in the thermostat elbow .
Tried blocking the mouth of the covoluted air hose to the throttle body, and found that it didn't pull right in or stall the engine. More evidence of an air leak.
Final test was to remove the jet from my propane blow torch, switch the gas on, and push the end of that in under the inlet manifold.
When it went near No 1, there was a distinct reaction from the engine.
Crack off the nuts holding the manifold, after removing everything else that gets in the way, and find that, after removing the water hose that gets in the way, the nut for the extreme left manifold stud was missing.
Took off the manifold, and half of No 1 gasket was missing!
How it could be in this state, and make no audiable noise when running I do not know.
The engine in question had been bought about eighteen months ago in a mint (except for crash damage) 325 SE insurance write off.
In the car were reams of mainly dealer invoices for repairs and servicing, and a two month old Ԛ£1000 + invoice for a brand new cylinder head complete and fitting.
Since my car was just in the process of turning its oil into mayo at the time, it was put straight in.
Obviously the prat who assembled the head had put the manifold on, then the water elbow complete with hose, and had missed the end nut.
Any of you near Belmont, in Surrey, be carefull where you take your cars.

Brianmoooore wrote: 2m length of hosepipe, one end in ear ,other probing around under the inlet manifold.

That bit made me chuckle

Nightmare! Always something simple in the end isnt it.

am glad to hear it was a fairly simple resolution in the end!!

and i must say, your level of perseverance is great-i'd have junked it by then!!

nice one! and i'll be aware of similar symptoms on mine

Sounds similar to the misfire problem on my 318iS. I brought it to a guy this week who found that the inner inlet manifold gasket had been replaced at some stage in the past and was put on wrong, how they could have done this is beyond understanding. This is causing a misfire in cylinder 4, which manifests itself as a very lumpy idle with strong fuel smell off the exhaust but is fine at driving speeds.

With this issue, the car should never have passed an MOT, but the car had a current MOT. I have a good mind to report these cowboys who issued it.

Hi guys,

I'm having a similar 5 min problem too. Hope someone can help..

I have a 325i se which runs on both petrol and lpg (mixer system before afm with no feedback loop and not gas injection).

Recently I too have been having a misfire which has got worse and worse to the point where it misfires on both petrol and lpg including at idle.

Easy enough I thought... half an hour job or so...

Quick rundown of whats been done: -

recently adjusted valve clearances and noticed dizzy and rotor weren't looking too good - replaced with new from gsf

Serviced inc plugs fuel and filter.

pulled all the leads and tested to find that they were all between 5.8 - 6.1 k ohms. Leads are all marked 5k ohms. Had a spare set on another 325 I own which is parked up so I swapped them over (tested these too before fitting and all around the same figure).

Tested the coil which I can't remember the exact readings but were in the right ball park (I think) will check again and post values here. Also the coil on the second car I have had similar readings.

Tested the coolant temp sensor, looked really old but was varying resistance nicely with temperature (changed it for a new one anyway while I had easy access).

Checked for air leaks as mentioned in this thread and could hear some noise from around no 1 cylinder (closest to cambelt). So got a new inlet manifold gasket and just finished changing that a little while ago. Had fun with the spring loaded pipe underneath! (Used a couple of small tie wraps to keep the spring compressed in the end - hth).

Also tested the tps which is working nicely, continuity with throttle closed, open after a few mm travel and then continuity accross the other two pins when it goes to around three quarters open.

Connector under inlet for injectors is very clean, even under the rubber at the bottom (cleaned it with electrical contact cleaner to be on the safe side).

after all that

...Its still the same.... if anything its actually got worse..!! Feels like its running on three or four cylinders and doesn't want to rev up easily.

I've given up for today and all I can think of to do next is check the afm (recently changed with the addition of a new anti-backfire valve - and I didn't think this affected the idle), not 100% sure how to test this, will see if I can find something on the forum. Also going to do a compression test as I'm now starting to worry.

Any help or advice gladly accepted... I'm losing the ability to think straight now

If you need any more information let me know and I'll check and post up asap.

Idle spped is at 750 - 850 rpm and not hunting apart from the misfire. I also recently checked and cleaned the contacts on the engine earth strap.

Holy thread bump Batman!

Adam318i wrote:Holy thread bump Batman!

Fooking hell Adam,long time no hear
Hows things mate,all good I hope?

Yea good thanks mate, good to see your still on here!

I've still got the SX (had it for about 2 1/2 years), looks like this now and running 275bhp;





Put with the cost of petrol etc going crazy its up for sale and guy is coming this teusday for it. Thinking of getting a handa integra type r next.

Hows you? still in Torquay? Ive still got that 318i rocker cover i bought off you sat in the garage! lol

^Nice rims mate

Yes im still here.Did take some time out from E30`s and got an E36 for a while but that didnt last long before I got bored so got myself another E30
Still in Torquay,well just outside in Newton Abbot actually.
Did a few jobs on your old 318 about 6 months ago for Barry but think it has been sold on again now?

Hey guys,
% bottle of rum and things are not seeming so bad

Even if its hard to type. Just seen the post date now
I was just going through all the search results before I posted and this hit the mark quite well....
Sorry, but if anyone has any ideas I'm all ears....

Although probably all passed out soon

Been back out testing and trying things again. So far I've pulled each lead one at a time while idling. Each one affected the running, but it still misses on idle and as its revved.

Then I tested the afm with it connected to loom and the ignition on.

a) 4.99 or 5v in (first 2 pins on left)

b) Increasing voltage from 0.25 upwards as the flap is opened (using first and third pins)

c) Air temp was showing around 2.2k ohms (first and last pins).

Tested the brand new coolant temp sensor just over 2k ohms.

I'm gonna make a cup of tea then write out everything I can think to test on paper and go through everything again.

Still looking for my compression tester but that will be the first thing I do.


Come on guys aren't there any ideas out there? Even if you think its something obvious please post up because it could do the trick..

Done the compression test, results are: -

Cylinder

1) 145 150
2) 150 150
3) 140 150
4) 130 130 130
5) 145 145
6) 150 150

All the plugs are sooted up but the last two (5 and 6) are very black.

I tested each cylinder twice to make sure I was getting good readings. Cylinder four I tested three times as it showed low for the first two times and the third time I put a little oil down the bore first but it was still the same.

I've noticed that the plugs that I recently changed are NGK ZGR5A. Are these ok with this engine? They were bought from car spares birmingham.

Where is everyone, any ideas at all??? I'm running out of options

The second car I have has a new crank position sensor. Might try swapping these over, but to be honest I'm getting fed up very quickly with this now.

Sticky/blocked/knackered injector?

Good try
but i've checked the injectors with a long screwdriver against my ear and they're all ticking away merrily.

Plus the problems there on both petrol and lpg which is a seperate system (I think)

thanks and keep them coming, I won't let this beat me...

Try the car on LPG with fuse 11 pulled in the fuse box.

Thanks for the idea Brian. I've just got up now so I'll be out, refit all the inlet pipes afm etc then I'll fire it up switch to lpg and pull fuse 11 out (is that the one for the fuel pump?). As sson as thats done I'll post up and let you know what happens.
But first... breakfast!!

Okay,

put plugs back in and reassembled inlet side again. Did as you said brian (started it on petrol first then switched to lpg and then pulled out fuse 11) even left it for a few minutes, but no change..

apart from when I first started it, for about a minute or so it was idling smoothly then quickly went back to its usual roughness.

Any more things I can check??

The test above was to see if the problem was duel fueling when on LPG and an over rich mixture on petrol at idle, both caused by a leaking diaphragm in the fuel pressure regulator.
If the diaphragm is leaking, it will allow petrol into the inlet manifold under high vacuum conditions through the vacuum sensing hose when running LPG, even if the petrol injectors are off. On petrol, the same problem will just make the idle mixture very rich by the same route.
I didn't think the test out too well, as there would still be pressure in the fuel rail for some time after fuse 11 had been pulled, so the results might be inconclusive.
Pull the FPR vacuum sensing hose off of its connector on the inlet manifold when running on petrol with the throttle closed, and see if there is any sign of petrol in the pipe.

Just want to say thanks for your help. I'll give that a try as soon as I wake up and let you know how it goes.

One other thing that I noticed was that the vapouriser on my lpg set up has the coolant pipes higher than the thermostat housing. I noticed it as I was starting to bleed the coolant system. It's a lo-gas system, are you aware of anyway to bleed the air from the coolant flow in this setup? I'm pretty sure there's gonna be air stuck in there.

I looked at taking it off and lowering it while I bleed the system but this looks too complicated/risky.

As well as car problems I'm now having computer problems too. Thankfully the computer only took several hours to fix... the cars are another story!

I did as you said Brian and ran it on petrol at idle (throttle closed) and pulled the vacuum hose off, but there was no sign of petrol there. Put it back on, let it idle some more and tried again but still nothing.

I even took it out for a drive with the vacuum hose disconnected and blocked and the car running on lpg but it made no difference. It misses on idle and throughout the rev range.

I managed to bleed the cooling system so don't worry about my previous post.

Any other ideas, this is really starting to get me down. I've already got a car thats supposed to not run right and be temperamental, ... a lancia .

I've thought that maybe a partially blocked exhaust could be causing this. So tomorrow I'll drop the exhaust at the manifold and see if that makes a difference, or shouldn't I bother just yet??

Looks like the faulty FPR/duel fuelling theory is going nowhere, unfortunately!
The usual advice for sorting faulty duel fuel cars is to sort the petrol running first and then the alternative fuel, but in your case it may be better the other way around, because on LPG things like the blue temperature sensor, TPS and AFM aren't relevant. If it's definitely not duel fuelling, then it'd down to a basic internal engine fault (compression, cam, valve seats, etc.), the ignition system, or an air leak in the inlet side.
Have you checked that any anti blowback device you have is sealing properly?
Have you any way of checking the mixture at idle?
What effect does removing the oil filler cap have on the idle quality?
Do you know how to adjust the vapouriser and screw thing in the gas vapour line? Is it possible that the LPG is just out of tune, and the petrol problem is just gummed injectors? (They can gum up if running almost exclusively on LPG.)

Hi Brian,
The blowback device did have a small air leak but that was fixed using some instant gasket.

Unfortunately I can't check the mixture at idle, but there is an mot station nearby, I'll see if I can use their analyzer.

If I take off the filler cap it does make the idle noticeably worse.

I don't exclusively run on lpg, I usually get through atleast £20 a month on petrol and when I had the inlet manifold off I took the injectors out and gave them a basic clean with carb cleaner. I didn't take them apart, just a kinda spray and pray. I know where the adjuster is on the vapour line but I have never messed with it. It looks straight forward enough, only out or in, although I don't know what will happen if I screw(lean?)/unscrew(rich?) it. I know where the screw is on the vapouriser too but same again I've never messed with it. I had it set up on an analyser by an lpg guy about a year ago but since then it hasn't been touched. Is there a diy procedure?

I did do a compression check as I was beginning to worry about something mechanical myself, the results are further back on the thread. Basically they're all around 150psi except for cylinder 4 which was at 130 and leaking past valves I think (bit of oil down bore didn't improve readings)

One thing to note is that when it's stone cold it runs and drives fine. I just took it out for a drive and it was fine for the first couple hundred yards (on petrol) then it starts to misfire again and run like poo.

Supafly wrote:One thing to note is that when it's stone cold it runs and drives fine. I just took it out for a drive and it was fine for the first couple hundred yards (on petrol) then it starts to misfire again and run like poo.

This is a classic symptom of problems with the engine coolant temperature (blue) sensor, or its wiring (connector under the inlet manifold), but would affect petrol running only.
What age is this car?
Any idea how the petrol system is disabled when running on LPG?

Unfortunately I have no idea how it is disabled. There are some extra wires that come over from where the vapouriser is and connect into some of the wires above the injectors. but thats about all I can see.

The car is a G plate 1990.

I tested the actual blue coolant temp sensor originally and it was reading fine but it looked very old/discoloured so when I had the inlet manifold off I changed it for a new one. Then i even checked the new sensor again and it was reading fine.

Previously I had a running problem which turned out to be the tps, during the fault finding then I checked the connector under the inlet and it was perfect, both at the pins and under the rubber boot (which was a pain to take off!). This time around I checked it again and it was still fine, I still cleaned it with some electrical contact cleaner.

Do you know what colour the wires are from the coolant temp sensor? I suppose I could test the resistance at the connector and also maybe at the ecu??

But as you say that should only affect petrol. Do you know what the standard readings should be for the coil? Could it be the coil breaking down under load? Any tests for this?

Coolant temp sensor wires are brown/orange (engine loom earth - goes to stud on RH suspension turret), and brown/red. This wire goes to pin 45 of the ECU plug, and the sensor resistance is checked between this pin and the ECU mounting bracket.
Coil resistances don't really mean much, as a few shorted turns would severly affect the performance of the coil, but hardly give any change in resistance at all.
They apparently get faulty coils in the US, but I've never come across one in the UK. Poor coil performance would be worse on LPG than on petrol, and worse at high revs and load than at idle, so I doubt if this is the problem.
Getting back to how the petrol system is disabled, I once diagnosed a faulty emulator on a dual fuel car that caused poor running, especially at idle on both petrol and LPG, by allowing dual fuelling, but E30s shouldn't even be fitted with an emulator.

This is really beginning to drive me nuts

Thanks for the help so far Brian, hopefully not much left to check. All I want is a smooth running six cylinder, is it too much to ask..

Anyway, enough of my rant, I'll test the resistance at the ecu tomorrow. But as you said the two systems are independant so cts, tps etc shouldn't affect it on lpg.

The garage wouldn't let me use their analyzer. There is an lpg place about 7 miles away, I might pop round there tomorrow and see if he'll have a look at the mixture.

My lpg setup is a very basic lo-gas one without lambda. Plus I ran the car for a good few miles with it switched over to gas and fuse 11 pulled out to see if it could be dual fuelling simultaneously. I drove it for around 9 miles on gas with the fuse pulled but it still ran like crap.

What is really baffling me is how it will run perfectly fine when absoloutely stone cold for about a minute or two max, then slowly start to get worse and worse over the next 60 seconds til its steadily missing again.

I swapped the coil anyway. Mainly because I'd run out of ideas and it was either that or start attacking it with a hammer! As you said the coil was fine, did the same with the new coil. I even checked the spark on each lead and it was a nice strong spark on each cylinder.

Do you know what pins the tps connect to at the ecu? I might as well check these at the ecu too. Plus it'll keep me away from the big persuader!!!

TPS connects to 52, 53 and earth, but again, has no significant effect on LPG running, with your extremely basic system. TPS, AFM and CTS might have a slight influence on ignition timing, but nothing that should upset the idle.
You really need to get a mixture analyser on the engine, to see if the poor idle is caused by a weak or rich mixture.
Have you checked the colour of the plugs? Any look different from the others?

I did check the plugs and they were all sooted up. The last two 5 and 6 were slightly darker than the others. The first two cylinders weren't as bad but still on the rich side.
I've got to check my dads car today... random knocking. So I doubt I'll have time to get mine over to the lpg guy. If I do I'll post the results up straight away.

Is there any way of checking the crank position sensor? Could this be the cause?

Sooted plugs suggest it's running rich, which would explain the lumpy idle. Only question is, why is it running rich on both fuels?
Doubt if it's the CPS, for the same reasons as I doubted it was the coil.