S50 B32 cutting out when warm.

[chriscotech]

I have had a rough idle during warmup for a while but it is usually o.k. once it is warm. Today my engine (S50 B32) was trying to stall once it had been sitting in traffic for a while. Not a cylinder misfiring but almost cutting out on all cylinders, every few seconds at its worst point. It also started revving higher for a while. My theory was that a sensor, possibly the crankshaft position sensor, was breaking down and the car went into limp mode. Does anyone think this sounds right? I am also wondering if the fuel pump could be cutting out for some reason. When it is running smoothly, it is running well with plenty of power.

I checked for codes but nothing showed up. It now seems to be running mostly ok again but every so often it gets shaky for a couple of seconds then sorts itself out again. I get a horrible feeling it is about to die by the side if the road. has anyone got any thoughts on what might be causing this please?

[wilhit10]

Did you disconnect the maf to check to see if that's it. Sometimes it can go bad without throughing a code.

[chriscotech]

Did you disconnect the maf to check to see if that's it. Sometimes it can go bad without throughing a code.

It's a good point, I have been keeping an eye on that. It once played up and I fixed it with contact cleaner on the plug. It was working this evening when I was reading live data off it but, like I said, the problem has been intermittent. If it starts cutting out again I will go straight to that. Do you know if it could cause it to start idling at about 1200 rpm for a few minutes then go back to 800?

In an ideal world I would substitute the MAF sensor, Crankshaft position sensor and fuel pump relay but I am pretty short of cash and they are all expensive.

[JCooper]

Does it just cut out only during idle or while driving as well?

[chriscotech]

Does it just cut out only during idle or while driving as well?

It was cutting out while driving too. The cutouts were very short and it only completely stalled once but they were happening every few seconds. This all started when I was sitting for ages at a stuck traffic light. I am thinking it was triggered by heat buildup, that's why I thought of the crankshaft position sensor, as it would have got hot. I took the car out later and it didn't cut out at all while driving, just an occasional "shudder" while idling. It was in the evening and cooler then.

I should also add that I took the fuel pump out recently to replace the pickup filter (it was loose and falling off ). I had a good look at the connections and it seems to be ok but I am not sure. At some stage it has been played with as it wasn't all the way down in its clamp and not picking up the last of the fuel. I also replaced the other level sender unit, which was broken. I obviously took the relay out at one point to relieve the pressure. I am not sure if this could have confused the ECU and caused the other problems.

When I last did some diagnostics to sort out the rough idle when cold problem the MAF sensor was reading 24.5 kg/h at 879 rpm.This seems high to me but I don't know what is normal. The coolant temp was 66ºC at the time as I was testing for cold start issues. If that is way off, does it point to a faulty MAF sensor or could it be something else making it read high? (I can't see how it could be tricked). How likely are they to fail?, it is definitely clean. A new genuine one is expensive. I was wondering if it would be safe to buy a used one of a car that is running well, assuming that is likely to be the problem.

[kovrol]

I had nearly the same problem, I can't tell it correctly cause I dont know this word in english. I had a rubber tube which gone wrong and the engine got "fars" air, I cant translate it correctly. My cold start idle was 1500rpm, 1mins later it lowered to around 1000. The car "ranked" till it get warm....after warmed it was good.
So it was a 20cm long rubber tube under the ITB, maybe it started from the bottom end towards upper areas...

[chriscotech]

I found one bad hose. It was not letting in air but in very bad condition. It was small and cost me $100. Unfortunately it did not fix the problem. I checked for vacuum leaks a few times but I am pretty sure there aren't any. I know this would cause the problem as it did with your car but I don't think it is the problem with mine. It only happens when it is hot. I am guessing that means it is electrical. I also tested the temperature sensor and it is o.k.

[kovrol]

just an info, I read your MAF "problem", as I know that the MAF can read around 800kg/h at 7000RPM....

[chriscotech]

just an info, I read your MAF "problem", as I know that the MAF can read around 800kg/h at 7000RPM....

Wow, I did not know that. That is almost one tonne of air every hour. No wonder these cars kick ass! Imagine the fuel bill for an hour at full throttle.

[kovrol]

yeah, I only know this because there was a thread in the US section where a guy wrote these from Germany, he worked at Bosch as I remember and got the info from there and you know the US 3.0L uses the euro MAF for tuning.

[Dejo325i]

I was talking to a friend from Perth, he has a friend with a 3.2 m3.. when the car would get warm it would start stalling and etc.. no codes and lots of $$$ later. The dme was the problem.

[chriscotech]

Oops. Not good news, I hope I am not so unlucky. Do you have any more information about the exact nature of the DME problem? Did it have to be replaced to could it be fixed?

[Rajvosa]

Oops. Not good news, I hope I am not so unlucky. Do you have any more information about the exact nature of the DME problem? Did it have to be replaced to could it be fixed?

my friends would only shut off in hot weather. swapped ecu with a friend and seemed to fix it...weird

anyone who can lend you their maf to try as that could be faulty

[Dejo325i]

I was talking to Ravjosa also a member on ecca, nope it just came up in conversation but I didn't ask much about it.

[wilhit10]

Best to just disconnect the maf, it'll give you a code, but the car should run ok. Run it that way for a week and see if you have the issue return. This is easy and free to check, why I would start there.

Cleaning maf's can fix it temporarily, but they typically need to be replaced.
Just my opinion from experience.

[chriscotech]

I have run it with the MAF disconnected and it is a bit rough but I am guessing it will adapt after a while. I would spend the money on a new MAF if I could be sure the high reading of 24.5 kg/h at 880 rpm was not caused by something else. From my understanding though, a MAF couldn't be tricked into a high reading, just a low one from a vacuum leak downstream. Can anyone verify that? I'm sort of convincing myself it has to be faulty though I thought they either worked or failed, not worked with way off readings. I have cleaned the MAF sensor several times with the proper cleaner. It doesn't look contaminated. Unfortunately I don't know anyone with am M3 MAF they could lend me. I might have to buy one and if it's not that I have an expensive spare.

By the way, the air intake on my car is standard (except a K&N panel which is not over oiled). Everything else is standard.

[JCooper]

Your crank sensor is taking a ***t! Happened to me on my 1st e36 and the original motor on this one prior too the euro swap. When they are on their last legs heat soak usually does exactly what you've explained. I replaced mine while doing the WP just to avoid the headaches.

[chriscotech]

I was thinking that too. I have had two go on another E36 in the past. The effect was the same but it didn't take long on the other car. I have one on order as we speak.

The other thing I was looking into today is the high airflow reading of 24.5 kg/h at idle. my 328i reads about 15 kg/h. I am convinced the MAF must be faulty. When it is disconnected it runs differently but no worse. Maybe better above 2,500 rpm, smoother warmup but a bit weak off idle. I think I need to cough up and get one. Somebody please stop me if my logic is flawed but I can't see how it can read high without being faulty. Where would that much extra air come from? It looks as clean as new.

[Impulsed7]

crank sensor, or something with the vanos or the fuel pressure regulator. mine would start acting funny at idle after warm and then when I restart the car, instantly dies. its the cams being out of position, if thats one of your issues. I did my fpr and vanos at the same time, now randomly after warm it won't stay running when I start it, but runs fine otherwise.

[chriscotech]

crank sensor, or something with the vanos or the fuel pressure regulator. mine would start acting funny at idle after warm and then when I restart the car, instantly dies. its the cams being out of position, if thats one of your issues. I did my fpr and vanos at the same time, now randomly after warm it won't stay running when I start it, but runs fine otherwise.

I haven't checked the fuel pressure yet but I completely rebuilt my vanos and calibrated the pressure to 100 bar. The live data shows the camshafts are moving correctly though there is a 1.9 degree difference between the "camshaft actual position" and the "camshaft nominal position" on both camshafts, though in opposite directions. I don't know if this is particularly bad in the scheme of 360 degrees of high speed rotation (you can see, there is a 5 degree tolerance for the ignition timing and you would think that would be more critical). All I know is that I timed them absolutely to the book and set the vanos oil pressure accurately.

Generally the engine runs very well. Still. I'd love to hear from somebody who properly understands those diagnostic figures. I really appreciate everyones help with this and promise to pass on whatever I find out.

[Impulsed7]

2 degree's off is a lot on camshaft position when variable.

[chriscotech]

I wonder what could be causing it? I am almost certain I could not have set the timing out by that much when I did the vanos and diaphragm springs. I am pretty sure the DME adjusts them to where it wants them. If it can see they are 2 degrees out, why doesn't it just correct them?

[JCooper]

I wonder what could be causing it? I am almost certain I could not have set the timing out by that much when I did the vanos and diaphragm springs. I am pretty sure the DME adjusts them to where it wants them. If it can see they are 2 degrees out, why doesn't it just correct them?

Mine was off by a deg also iirc. I'll see if I can dig up the video of when I record the live cam readings. This could possibly be normal.

[chriscotech]

Mine was off by a deg also iirc. I'll see if I can dig up the video of when I record the live cam readings. This could possibly be normal.

It would be good to see what yours was doing. I think you could be right about it being normal. I know there is something else going on with my engine. I imagine the ECU is making adjustments based on the other info it has available. In my case a high airflow reading. A new MAF sensor is on its way. I'll report back when it's on the car. I will also replace the crankshaft sensor. If that is what is causing the cutout it could leave me in the S**t with no notice.

[boxter]

2 degree off is absolutly normal. My car and other m3, when I read them with DIS, obtaining 2 degrees off (intake) and only 0.1º for exhaust.