M50 Stalling During Warm-Up......Help...

[Dave M]

Prior to rebuilding the M50, I had intermittent issues with the CEL illuminating and an associated erratic idle (both very short term). The problem would arise either on a cold start or (once) at highway speed. On a cold start, the idle would be erratic, but after re-starting would become normal. On the highway, the CEL would illuminate and when the clutch pedal was pressed, a high idle (@2000 rpm) would result.

Now,

Since rebuilding the M50, it has resurfaced, but slightly different and much worse. Recently, on a few occasions, when the morning temp was @ 0 celcius (32 F), it ran fine until ‘mid-warm’ (thermo open, not yet at operating temp). Usually about 5 min into the drive, the CEL will illuminate for a split second and the car will stall (head snaps forward, foot hammers clutch). This morning was the worst. It happened a number of times and I had to limp it into a parking lot. For the first time, it actually stalled while simply idling. I started again, but only after a few attempts.

Now, I know the battery connections are fine and I shouldn’t have a vacuum issue (replaced a bunch of related parts during the rebuild). I haven’t re-checked plugs etc, but will do so this evening (don’t suspect). Also, no fuel leaks or difficulty starting.

What gives? I have searched the achives and come up with a few ideas. What do you all think?

Old Post
Temp Sensor On Thermo (http://www.bimmer.info/forum/showthread.php?p=144619&mode=linear&highlight=hesitation+temperature#post144619)

Other Ideas

-Fuel Pump/Filter
-Fuel lines
-Fusible link on passenger side engine compartment

As usual, I really appreciated any input,

Dave M

[Jon K]

crank position sensor good?

[joshua43214]

Any codes? you should get a code set when the CEL comes on.

[632 Regal]

right, and that should help zero in on the issue.
Any codes? you should get a code set when the CEL comes on.

[Dave M]

right, and that should help zero in on the issue.


Problem is…….

I’ve never been able to retrieve faultcodes. Mind you, I’ve only tried a handful of times with no luck. I assumed since it was purchased in Canada, I don’t have the ‘option’. I’ve asked this before with no response, but I’ll try again. Is anyone with a Canadian bought e34 able to retrieve codes with the Stomp Test?

How would I check the crank position sensor?

Thanks guys,

Dave M

[Dave M]

Any codes? you should get a code set when the CEL comes on.


Well, went out to the car and did the stomp test. Got a 1444, so no luck yet. If it stumbles and the CEL flashes on for an instant,will it recallthe fault a few hours later, or does he CEL have to stay on?

Dave M

[632 Regal]

it should store the code for a long time.
Well, went out to the car and did the stomp test. Got a 1444, so no luck yet. If it stumbles and the CEL flashes on for an instant,will it recallthe fault a few hours later, or does he CEL have to stay on?

Dave M

[joshua43214]

I can't recall if the older e34's have any codes that don't store, some cars won't store certain codes after the CEL goes off.

Assuming older e34's store all codes any time the CEL comes on, logic would say that having no codes stored would mean the DME reset after the car stalled, or there was no fault detected, meaning the problem lies in systems beyond the DME to fault(fuel pump, coil,etc).

Start with the basics, something as simple as a partly blown fuse could be the culprit. Check the fusible links and closely inspect all the fuses to the DME for internal breaks, the low amp ones often won't have scorch marks, so replace if any doubt.

Check the grounds, especialy the one rearward of the RH shock tower kinda behind the electronics box. Loosen and retighten the grounding points. Look for loose ground wires from an earlier service.

Intermittant problems like these can be a bear to find. My experience is that I either find the problem right away, or I have to chase it arround for a long time. A really experienced tech can usualy tell if you are losing fuel or spark by the way it feels when it stalls, Might be worth getting a buddy that has this kind of experience or bribing one to drive it. Could something as simple as a relay shutting off power to the coils(or bad coil) or fuel pump and the CEL is just the normal light check when the key is on engine off.

eventualy it will probably do a hard failure and then it will easy to pin down, unfortunately you could be any where when that happens.

Either way, no codes present is a clue, many possibilities as what is is causing the stall. Try to keep diagnosis as simple and basic as possible, most driveability issues have simple faults that seem obviouse on hind sight, paying close attention to every symptom can often lead you to the problem, IE, engine goes instantly dead is often ignition related(or injector), cars sputters or RPM climbs is often fuel supply related.

[Dave M]

Could something as simple as a relay shutting off power to the coils(or bad coil) or fuel pump and the CEL is just the normal light check when the key is on engine off.


IE, engine goes instantly dead is often ignition related(or injector), cars sputters or RPM climbs is often fuel supply related.

Joshua,

Thanks for the help. You're probably right about the CEL 'flashing' due to an ignition shut off rather than a readable fault. Its pretty violent when it happens so I wouldn't be surprised if its just kick-starting itself after each shut down. Certainly feels ignition related.

If this is the case, do you or anyone else have any more leads. I'm taking the advice provided and will check the fusible link on the strut tower and poke around elsewhere for other fuse failures. I'm real $hitty with electronics, so I may need some help.

Still, its still odd that it happens only during warm-up. Eventually though, it will leave me stranded :(

Thanks again,

Dave M

[joshua43214]

Hopefully if you don't find it right off looking at fuses and the like, you will get a flood of " i had the exact same problem,caused by XXXX"

Just check every thing people say caused the problem, I've seen this sort of thing caused by every thing from a key chain that had to many keys and would turn the ignition off and on when it swung to a coil that shorts out only at a certain temp, and was fine at all other temps.