Car running on 3 cylinders

[JOEPM3]

Hi all,

I have an issue with my E30 M3 that it only runs on 3 cylinders and so far I haven't been able to problem solve it so hope someone here can help!

Below some details what the symptoms are/what has been done. Haven't driven the car much in recent years (maybe 250-300 kilometers in total in the past 2 years) due to being quite busy (small kids ) and the car experiencing all kinds of small problems preventing much use.

• Spring 2022: changed all fuel hoses, thereafter car would run on 4 cylinders right upon start
• Summer 2022: changed spark plugs and some other small things, car would run on 4 cylinders right upon start
• Autumn 2022: when some small issues were fixed and the car got a fresh MOT and I wanted to use it, it suddenly ran on 3 cylinders upon start - driving a few km didn't help so put it back in the garage again. Decided to take out the injectors and had them professionally (ultrasonic) cleaned. Put them back in and tested the car and it ran on 4 cylinders right upon start again. Stored the car for the winter, hoping for a 2023 season that it would see more use
• Spring 2023: took the car out of storage and it started again only on 3 cylinders, switched to 4 cylinders after a short time (few mins or so)
• Summer 2023: used the car a few times and it would constantly start on 3 cylinders upon cold start in the garage to switch to 4 cylinders after a while, say after 5-7 kms of driving and the engine got warmer. Didn't matter if there was 1 week between usage or only 2 days, however starting the car on the same day after initial use it would always start on 4 cylinders, whether it had been off for minutes or for 4-6 hours (so the engine could cool off). After no use for a month, the car would not switch to 4 cylinders anymore (I stopped driving after 15 kilometers) last weekend.

Since I have checked the spark plugs again and all 4 have a spark and look nice "light chocolate", can't really see any differences between them to tell what cylinder is causing problems. Also did a sanity check on other items (vacuum, etc.) and all seems to be fine. Suspecting the injectors again but I find it strange since they were tested/cleaned last year and when the engine got warmer it would run on 4 cylinders without any issues. So I would put the car in the garage running perfectly and on cold start a few days later it would only run on 3 cylinders again, therefore it doesn't seem like a sticky injector to me.

Anyone some suggestions what it could be? Otherwise I plan on taking out the injectors again and have them cleaned/tested again to see if it makes a difference. I also have looked at buying simply 4 new injectors but can't find any online (every shop seems to be out of stock).

Apologies for all the details but I'm a bit puzzled.

Thanks for any input!

Best,
Joep

[Mick]

Are you sure it's running on 3 cylinders and not just "running rough"?

How old is the fuel that's in it? I've had issues where the car runs like crap until warmed if it has old fuel.

[CamayroZ]

Joep,
Do you put stabilizers in your fuel tank and perhaps run non-ethanol fuel?

I was going to suggest cleaning your injectors, but you have done that. Did they flow them as well, I hope?

I am assuming that your battery is good/strong and not doing funny stuff?

To have more trouble shooting information, the next time that it is running on 3 cylinders, use your hand/thermal gun to see which cylinder is not getting warm fast enough?

Is there any way that you can add some fuel injector cleaner/other cleaners/and run one tank of fuel through your engine before you start wrenching again? IE) Go for a 300km trip and excercise the engine?

[bladsville]

You can figure out which plug isnt firing by disconnecting a plug wire or injector plug one by one and listen to see if the idle changes. Once you have no change in idle then you found the culprit. From there you can see if its either no spark or no fuel condition.

The only time I had an intermittent loss of a cylinder firing like you are explaining was when one of my spark plug wires was chaffed by being in the plastic prison BMW designed. I guess once the shielding was rubbed away it would ground out and cause the plug not to fire.

[davem3]

Rubber blokken lekken die tussen de kop en de gaskleppen zit
kop zet door warmte iets uit en is hij dicht

Gr dave

[JOEPM3]

Hi all,

Thanks for the input/thoughts!

Some feedback:

• Fuel is 1 year old, is premium quality 102 RON fuel
• Injectors were tested on flow I understand from the shop who cleaned them
• Battery seems to be good, it is able to turn the engine easily
• I don't feel like driving too much on 3 cylinders since I'm worried about damaging something (i.e. crank) due to unbalance in the engine
• Good suggestion about pulling the plug wires to see which cylinder it is - will try
• If it would be rubber blocks between cylinder head and valves that expand a bit when the engine warms up, why would it then now not switch to 4 cylinders at all anymore and why would it not cause issues when the engine was cooled down after being off for > 5 hours and then fired up again (on a single day)?

Best,
Joep

[bladsville]

• Injectors were tested on flow I understand from the shop who cleaned them

FWIW, I had a set of injectors cleaned and tested by a reputable company just to get a set sent back with one dead injector. It happens, not saying this is the case for you.

[HANDBLT]

Hi all,

Thanks for the input/thoughts!

Some feedback:

• Fuel is 1 year old, is premium quality 102 RON fuel
• Injectors were tested on flow I understand from the shop who cleaned them
• Battery seems to be good, it is able to turn the engine easily
• I don't feel like driving too much on 3 cylinders since I'm worried about damaging something (i.e. crank) due to unbalance in the engine
• Good suggestion about pulling the plug wires to see which cylinder it is - will try
• If it would be rubber blocks between cylinder head and valves that expand a bit when the engine warms up, why would it then now not switch to 4 cylinders at all anymore and why would it not cause issues when the engine was cooled down after being off for > 5 hours and then fired up again (on a single day)?

Best,
Joep

If you don't have an IR temp gun to check which header tube is not getting hot, just revert back to old skool shade tree means. Spit on each one and one won't sizzle

T

[CamayroZ]

Hi all,

Thanks for the input/thoughts!

Some feedback:

• Fuel is 1 year old, is premium quality 102 RON fuel
• Injectors were tested on flow I understand from the shop who cleaned them
• Battery seems to be good, it is able to turn the engine easily
• I don't feel like driving too much on 3 cylinders since I'm worried about damaging something (i.e. crank) due to unbalance in the engine
• Good suggestion about pulling the plug wires to see which cylinder it is - will try
• If it would be rubber blocks between cylinder head and valves that expand a bit when the engine warms up, why would it then now not switch to 4 cylinders at all anymore and why would it not cause issues when the engine was cooled down after being off for > 5 hours and then fired up again (on a single day)?

Best,
Joep

Joep,
In the US, our fuel is ethanol blended and ages rapidly. I always buy “pure” non-ethanol and blend stabilizer with it to avoid fuel related issues as much as possible.

I still think that once you start the car, and it “clears” itself up, you should consider running one tank through it. At least that’s what I would do to my car.

great idea to see which cylinder is not warming up as quickly.

best of luck.

[hardtailer]

102 RON is ethanol free or 2.5% max here in Europe.
Your problem is not caused by old fuel.

I suspect the wiring to the injector is the culprit.
Check if all 4 receive +12V when the ignition is on.
The injectors are fired by the ECU via switching 1+2 and 3+4 to ground in alternating fashion, 180° crank degrees apart.
The loom inside the plastic casing with injector connectors branches from one single +12V wire into 4 individual wires to supply all 4 injectors.
similar for 1 'switching to ground' wire that branches out into 2 wires going to injectors 1 and 2 as well as another 'switching to ground' wire that branches out into 2 wires going to injectors 3+4.
I suspect that one of these branches no longer provide a good connection to one of the injectors.

If you pull the spark plug leads off one by one while the engine is running, then wear insulated gloves else you risk being zapped by high voltage.
Better yet, pull each lead with the engine switched off and connect it to ground. Only then run the engine.
Repeat 3 more times to find out which cilinder is not injecting.

Tell us what you find!

[JOEPM3]

Hi guys,

As an update, I have tested the injectors first by pulling them out of the head and see which ones were spraying. Noticed that not all of them were spraying and when changing the non sparying injector to another cylinder, the non-spraying sympotom moved with it.

That told me it should be the injectors so had them again professionally tested and cleaned. Now they also changed the internal filters. However, the injectors were already perfectly working prior to the cleaning/replacing filters and the result after were only marginally (1-2%) better. Hence, was quite puzzled.

Put them back in and started the car, it ran on 4 cylnders right away. Hence, happy that is running good again but absolutely puzzled on the route to get there given the test results of the injectors pre and post cleaning/filter replacement.

Any ideas how this can be?

Best,
Joep

[hardtailer]

Thanks for the update. Seems to me you havent done the checks I posted in post #10.
That is also how I would answer your last question: contact issue between wiring loom connectors and individual injectors

[Ron ///Man]

I've seen this exact behavior many times with different E30 M3's. The injectors stick, even not long after being professionally cleaned. My own cars would do this routinely after I stored them for the winters. Typically, I'd tap on the top of the injector's with the soft side of the spark plug "T" wrench and most often, the stuck injector would start to fire. After driving it around for a bit, the problem usually went away until after the next winter storage when it repeated again, as did I...!! Not sure if these injectors are prone to this due to being 'old' technology, and / or low impedance, but injectors in newer cars don't seem to suffer this ilk.

[CamayroZ]

I've seen this exact behavior many times with different E30 M3's. The injectors stick, even not long after being professionally cleaned. My own cars would do this routinely after I stored them for the winters. Typically, I'd tap on the top of the injector's with the soft side of the spark plug "T" wrench and most often, the stuck injector would start to fire. After driving it around for a bit, the problem usually went away until after the next winter storage when it repeated again, as did I...!! Not sure if these injectors are prone to this due to being 'old' technology, and / or low impedance, but injectors in newer cars don't seem to suffer this ilk.

Ron ///Man this is exactly my experience as well. I have done that for many many years, as my car sees a few hundred miles per year and that's it. About 5 years ago I switched to all-year long non-ethanol and Stabil and I have never had to tap on them again. I have no clue why! But I only have 35 years of experience with my car.