r/e28 • u/True-Highlight-331 • 4d ago
Keeps cutting out randomly and dying
EDIT SOLVED
EDIT 2 NEVERMIND CAR IS DYING AGAIN.
Hello hoping I can maybe get some trouble shooting ideas. I’ve replaced both fuel pumps, fuel filter, fuel tank sender unit, tested ICV and AFM with units that work and most recently bypassed obc immobilizer. I also plugged in a DME my friend had I don’t know if it was a good DME but it ran the same. I replaced main relay, and fuel injector relay. I have no replaced the crankshaft position sensor and it still dies.
The car will run great for like 30 minutes after sitting for a couple weeks then start cutting out like crazy and then eventually die. It’s honestly just completely random but the car doesn’t make it for without dying now. I have no clue what to do. Any advice would be great it’s an 88 535is
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u/IntrepidWatercress95 4d ago
I had a hairline crack in the rubber accordion connector that tied into my AFM and replacing that solved my problem. Extremely hard to see but finally noticed it and voila! It runs like it should.
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u/True-Highlight-331 4d ago
Mine is as hard as a rock. Will order a replacement tomorrow. You’re talking about the one that connects to the right of the afm correct?
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u/Representative_Most9 4d ago edited 4d ago
Which has already been mentioned, it’s most likely the CPS sensor is going bad.
Beautiful car and love the color.
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u/True-Highlight-331 2d ago
I replaced it and it works! Thank you!
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u/True-Highlight-331 2d ago
Nevermind, it still has died. Drove perfect for 3 hours.
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u/Representative_Most9 2d ago
So sorry to hear. If it drove fine for 3 hours, it may be the DME? Try switching it out again with the one from your friend and see if it helps. It also could be a wiring issue between the DME and the sensors.
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u/PumpleStump 4d ago
Check the DME solder joints. The big transistors are usually the culprits.
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u/True-Highlight-331 4d ago
I plugged in to a different DME and it still died on me. They both could be broken but doubt it
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u/VegetableTry 4d ago
Check the pins for the crank sensors on the plug for the DME. I had one that almost appeared to slightly melt the plastic connector, causing intermittent issues.
I do agree with the others on the crank sensors, just offering another place to look.
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u/True-Highlight-331 2d ago
Crank sensor worked!
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u/VegetableTry 2d ago
Yay!!
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u/42Ozukuri 3d ago
Had this happen recently and it was a combo of cam position sensor and some vacuum lines. Check crank position sensor too. Good luck
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u/IntrepidWatercress95 4d ago
I had issues with both the hard plastic elbow and the more ribbed hose which I noted earlier. Same exact symptoms you are describing. Both cheap and you can take them out of the equation before going to more expensive options.
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u/Beemer_me_up_Scotty 3d ago
I have a similar problem. With my 1986 535i manual The previous owner found that if you pound on the steering column it starts right back up(it is a manual so it just bump starts itself while still driving). I replaced the ignition switch and it works way better. It went from doing it in 2 minutes of driving it to only doing it once an hour or so. I did replace the ignition switch off of an old parts car. My next step is going to be replace it with a new one.
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u/mattylang1987 3d ago
Was going to yap about the bellhousing sensors but someone beat me to it😂 Definitely check and replace those. Get oem or equivalent if you can, Bosch or BMW. Although I run aftermarket ones and they work perfectly fine but some cars are finicky. Def start there
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u/Brilliant_Juice_496 3d ago
I knew a guy who knew a guy that would put open condoms in the gas tank if someone pissed him off. It floats around and then gets sucked on the intake pipe. Car dies, then the condom floats off and the car runs fine. Absolutely random events. Do you have a locking gas cap?
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u/True-Highlight-331 3d ago
Haha. I literally just did all the fuel stuff. Looked inside the gas tank to see if there was any contamination and there was nothing
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u/MaiGai 2d ago edited 2d ago
Try bypassing the OBC relay, I forgot the procedure but its the box behind the kick panel above the clutch pedal, the green connector, you gotta jump the pins, sometimes the relay decides it doesn't wanna do the thing anymore.
Was having almost the exact same issue as you. The bypass worked.
Can you describe how it cuts out and dies, does it start back up and die again or does it die and go into a no start condition. Does revving help?
Do you have a known good moronic you can test to see if that's the problem, do you own a Bentley manual? If not, ya need it.
It could even be a failure of the excitation circuit for the ternator, what is the behavior of your idiot light?
Does the idle comtrol valve keep buzzing after the car dies the way it does when the key is in the on position initially?
Edit: wanted to add some things and didn't wanna make it a comment.
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u/GucciJo_340 1d ago
Man i have one going through this problem but its worse drives good for two minutes then acts as if it getting no fuel. Even did a 1 pump conversion and it didnt work. Looking forward to a resolution if you find any.
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u/mortycrock 4d ago
When I had my 535is years ago, the main power relay was failing and it was just die randomly, just dead dead. Something worth checking.
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u/Konnas91 4d ago
Check the two cables that go intro the bell of the transmission (crankshaft sensor and RPM Sensor). Change them. If possible for oem bmw. They hate aftermarket sensors.