Car cuts off while driving

[E30_fiend]

buy a can of CRC or the like electric terminal cleaner and go to town on your main realy and fuel pump relay terminals. Get some fine grit sandpaper and sand the relay prongs til they are nice and shiny. If this doesnt fix your problem then all roads lead to a faulty ECU. At least this way it will only cost you 6-8 bucks and 30 minutes of your time.







Taylor

[E30QC]

same prob. but in freezing weather,
new flywheel, engine position sensor.
eta

[chau]

having the same problem with my 86 325es. Car just cuts off smoothly while driving. Sometimes it will start up again just fine. Other times I would have to wait around 10-15 on the side of the road before it starts up again. Thanks for the tips guys, I'll check the relays first.

[StereoInstaller1]

Guys, I am gonna say it again: TEST THE MAIN RELAY FIRST.

For your edumacation, let me 'splain what happens, and why.

Every time you turn your key on, 2 contacts inside that relay connect. Every time you turn it off they disconnect...each time, there is a tiny spark, each time there is a tiny bit of carbon built up and a tiny bit of wear.

Give it 20 years and the resistance is gonna skyrocket.

Add a bunch of heat and the resistance goes even higher, so now all of those circuits that depend on that main relay are now on the brink of shutting down...now a little bump gets transmitted to those contacts and everything dies.

Simply using your car is gonna heat up that contact too!

Now, keep in mind: this is THE ONLY relay in the whole damn car that runs both fuel AND spark, and this is also the only relay in the whole damn car that uses 2 contacts at the same time.

This relay has more stress on it than any other relay in the whole car, period.

Now, gloriously enough, it is really easy to bypass for testing purposes.

Grab yourself 3 male 1/4" spade lugs and a foot or so of 18ga wire.

Make 2 lengths of wire about 2' each and then connect the wires in daisy chain fashion.

Now, grab that relay and yank it out, removing the socket from its holder too.

Look on the bottom, look for the 3 fatter wires. Use that handy daisy chained connection to plug all 3 of them together.

Go start your car and drive it half an hour or so, or however long it takes for it to screw up normally. If no issues, but a damn relay.

Oh...your car may or may not shut off when you get to where you are going, so pull those jumper wires off. Your car will shut down, no worries.

GL,
Luke

[Mde36]

I forgot I even made this thread, the car doesn't even have an M20 anymore but thanks for the helpful information

[StereoInstaller1]

Same shit applies to damn near any BMW

[long tall eta]

did any body ever sort this gremlin out. my eta is doing the same thing. i keep reading about peoples problems but knowone ever comes back and says ( hey i got it, it was this)