Still working on my M50 stall/studder issue, couple questions....

[Dave M]

Hello all,

Been tinkering a bit more with my M50 studdering issue. Again, for those of you who haven't seen my previous thread, during the warm up period, it will almost die or completely die at idle, or, when driving, will violently studder as though the ignition is quickly cut-off and turned back on. I get a quick CEL flash and then everything is back to normal until the next one. Once the car reaches operating temp, everything is fine.

So far I've swapped:

Throttle potentiometer (throttle position sensor)
Air temp sensor
engine temp sensor
MAF
ICV (clean as a whistle)
All six coils
All of the above was provided by our own Ryan R. Thanks again.

I've also used contact cleaner on every terminal/connector i could get my hands on.

However, none of the above has made a difference, so...........I'll soon be receiving and swapping:

coolant temp sensor
DME and fuel presssure relays

Last night, I had the car idling outside in the cold (-8 C)with the lights on and was playing with various electricals to try and instigate a stall (it has stalled instantly when I've turned on the blower fan while idling idle). No luck, but i noticed that the lights would dim and the idle would drop each time the defrost or fan was turned on (idle would also get rougher). The idle is already low (~600rpm) and 'm wonder if I dealing with an alternator issue. I've tested the batt with a multimeter (OK), but have not unlocked the OBC to try the test.

So my questions. Should this dimming occur? At some point does the engine say "f'ck you, not enough juice, I'm shuttin er down"? Its odd that it has only occured during warm up (so far).

Anyhow, thanks for reading, I'll repost when I swap in relays/sensors.

Dave M

[White535Mtl]

I've been having the same symptoms as you, except that mine occurs at any temperature.

Very interested in finding out what the culprit would be.

[632 Regal]

Dave from what I follow I think you are on the right track with the voltage issue. nothing dims on my car no matter what I use. Low voltage can cause all sorts of issues, you must be at some limit cause the car shouldnt run past a certain point. I think you should research the OBC voltage testing and see what is actually going on while it is running. Maybe the brushes are going and sometimes falters causing the stall.

[///M-Power 3\\\]

Hello all,

Been tinkering a bit more with my M50 studdering issue. Again, for those of you who haven't seen my previous thread, during the warm up period, it will almost die or completely die at idle, or, when driving, will violently studder as though the ignition is quickly cut-off and turned back on. I get a quick CEL flash and then everything is back to normal until the next one. Once the car reaches operating temp, everything is fine.

So far I've swapped:

Throttle potentiometer (throttle position sensor)
Air temp sensor
engine temp sensor
MAF
ICV (clean as a whistle)
All six coils
All of the above was provided by our own Ryan R. Thanks again.

I've also used contact cleaner on every terminal/connector i could get my hands on.

However, none of the above has made a difference, so...........I'll soon be receiving and swapping:

coolant temp sensor
DME and fuel presssure relays

Last night, I had the car idling outside in the cold (-8 C)with the lights on and was playing with various electricals to try and instigate a stall (it has stalled instantly when I've turned on the blower fan while idling idle). No luck, but i noticed that the lights would dim and the idle would drop each time the defrost or fan was turned on (idle would also get rougher). The idle is already low (~600rpm) and 'm wonder if I dealing with an alternator issue. I've tested the batt with a multimeter (OK), but have not unlocked the OBC to try the test.

So my questions. Should this dimming occur? At some point does the engine say "f'ck you, not enough juice, I'm shuttin er down"? Its odd that it has only occured during warm up (so far).

Anyhow, thanks for reading, I'll repost when I swap in relays/sensors.

Dave M

I had this problem on a customers '95 525i at work, we tried everything and it still died. Turned out to be a vacuum leak in the weird hose that is under the intake manifold and connects to idle control valve

[Dave M]

Thanks all,

White 535,

keep watch as we're gonna skin this.

Jeff,

I'd like to think I'm on the right track as I've systematically (sorta) ruled out quite a few things. If the relays, coolant temp sensor AND alternator aren't it, I've already spoken with Mark D to locate a working DME to swap in. I'll do some research on testing the alternator (maybe just bring it to someone??) and may be back asking questions on that subject this weekend.

M Power

When I had my head off the first time last year, I actually rigged a clamp (drill and wire) to better secure that 'macaroni ICV to intake hose'.

I'm pretty confident its not the source, but I will inevitably have the manifold off again this winter and will double check that connection again. I've eaten lots of words, mmmmmmmmm.

Over and out, passed out that is

[Dave M]

Hey, just checked around i the archives and found a couple which discussed the diffs b/w digital multimeter (DMM) testing and the OBC test (which I've never done).

Now, I've never done the OBC test and I'm wondering whether there is any advantage to it? The posts refer to discrepencies b/w the two and insinuate that the 'fault' lies in the OBC test. Oh, I have a multimeter and have tested the batt with it. Also I'm gonna try it again this weekend as per bentley and make sure I have enough load on it. Page 121-2 Oooh, oooh, and the alternator checkaroo on page 121-3, what fun!!!

out