SLOVED!!! ANY Ideas?? Spark / Ignition Cutting out

[jlevie]

Been there, done that. I chased the same kind of problem on my first & second race cars for over a year before solving it, though my problem was more intermittent. During that time everything in the engine management system was changed at least twice and the engine anc car body changed once after the first car was wrecked. Ultimately I found the problem by watching a battery powered o-scope monitoring the CPS input to the DME while a helper drove the car. When the wave form distorted, the cut-out occurred. Changing the CPS and running the same test had no affect, so it had to be the engine harness. The fourth used harness (I'd already changed the harness once) I tried was the winner. Well until until it suffered an internal hemorrhage six months later that took out the coolant temp sensor signals, which was replaced with a brand new harness from BMW.

For clarification on this problem, was the harness a new part from BMW? Have you tried a different new BMW CPS? When changing the CPS was it's cable routed through the plastic wire chase behind the water pump pulley or over the top of the head where the water pump pulley can't abrade it?

[ct3155]

Ok so I finally switched to a good known working dme. Still no luck. Hard to start.. Have to give it a decent amount of gas petal to run the rpms up high enough to keep it holding on while it's cutting out with the check engine light flashing still.... That's what's so Weird. That light flashing while it's running like crap. Then the light turns out for good and it will settle out... Any more ideas??

[mucoyekul87ETA]

I've now put in a known good and working DME in, all problems have gone by the wayside...

[mucoyekul87ETA]

I am going to try and source a known good DME for mine as well, but I am so baffled that I am still not convinced about where/why the issue arises. As I said, after using a (borrowed) good DME, the normal driving cutting out seems to have gone away, but still not sure I trust it. However, I am certain that the good DME fixes the cutting out under load @4000rpm. I'm going drive with the old DME that I had minor problems with before and see if the cutting out (the mini cut-outs) comes back.

You sound like me, I have a great 325 that never has any running issues, but right now I am battling a no-start issue with her! Which could be DME related as well. Too bad they are different DME's it would make testing and sourcing computers much less of a hassle.

[ct3155]

Nope. Hadn't quite solved it yet. I've cleaned the connectors super well and even put dielectric greese in them... Still having the issue!!

Luckily for me the problem is in my summer toy. So I've since put it away for winter and will continue to (slowly) diagnose when I have the time. I am currently driving the winter vehicle hahaha! Bone stock 325e. No cutting out there!!!

Honestly the only thing I can think of to try swapping out dmes again. I have only used one 173... It was known good.. But maybe not with the increased vibration from the solid motor and trans mounts. I will report back when I get my hands on another 173

[mucoyekul87ETA]

This is absolutely nuts. I am and have been experiencing the exact same issues with my 89is. CT u describe it exactly the same as my issues. Its WACK I threw a different DME in and the car stopped cutting out under load and pulled well past the 4000rpm mark where it would cut out/engine check flash/ etc. However, it still had the little hiccup/check engine flash/cut out/return to normal after having been driven for a while, not particularly under heavy load or anything. I kept driving her for about 100 miles last week while using that DME the hiccups have stopped, but I have a hard time duplicating the problem when I want to. You solve this annoying shit for yourself yet?

[SpecM]

bump for help

[SpecM]

more often than not, my car is doing the same thing but at lower rpms, ie when comming to a stop with clutch in and rpms droping. it will cut off sometimes

stomp test shows code 1261 - fuel pump relay control, which indicates an issue with rpm signal (usually)

[FLG]

Ok I'll for sure give it another go..

I just find it so Weird that it only happens under load. Can never replicate it when just in neutral.

Same issue I had.

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[ct3155]

Ok I'll for sure give it another go..

I just find it so Weird that it only happens under load. Can never replicate it when just in neutral.

[FLG]

Nah that wouldn't cause an issue. Most people prob never torque those to spec.

I remember doing this for weeks and it turned out to be the c101 connector. I know you cleaned it but clean it more, remove the rubber boots and inspect all the wires.

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[ct3155]

Here are some of my current thoughts all sparked by FLG.

I know that when I reinstalled my harmonic dampened toothed wheel / pulley assembly, I didn't bother to look up torque specs. I just tightened down to what I thought was good. This method would most likely not give the five bolts a uniform torque... Wonder if it causes a vibration of some sort at certain rpms??

Also here is news specific to my car. Don't know what it means but who has a thought on this?? I can never ever no matter how hard I try, replicate the cut / loss of timing in neutral aka under no load really. I can rev all matter of ways to all its usual trouble rpms. Never can I make it cut.

However, the second I put it in gear and pull up to speed with some authority (not flat foot but closer to it) I can make it cut every time. Damn. So it's load related. Also, it happens more when it's colder outside... Take that all for what it's worth.

Who has ideas on that??

[SpecM]

anyone else have an idea?

[FLG]

I might be wrong but I think tho solid it is 2 pieces with rubber holding it to the center. Check Google I'm currently on my phone and its a bit hard to search.

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[ct3155]

Another possible issue is a bad harmonic balancer that's separated causing the ring around that the cps uses to not spin with the engine causing issues with timing.

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Ive had the harmonic balancer off this summer when i did the timing belt. Isnt it one piece?? I mean it has the pulley that sits inside it that can separate.. But I thought the toothed wheel (its heavy too) Was one solid chunk??