Car cuts off while driving

[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)

[StereoInstaller1]

Same shit applies to damn near any BMW

[Mde36]

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

[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

[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.

[E30QC]

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

[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

[Slangbox]

Damnit... today it hit 105, which is a record for my area, and my car did the same thing. FML.

[Adiabatic]

nth-ing the electrical problem diagnosis. Next hot day backprobe power to the DME and/or signal from ignition control circuits (crank pos sensor, flywheel sensor, cam pos sensor, distributor gear sensor, whatever an M20 has) and see if any drop off suddenly when the problem repeats. I'd bet money on ignition control, but thats just because I've seen it happen before, albeit on a different vehicle. After eliminating those possibilities I'd backprobe the fuel pump after the relay or swap out DMEs.

[Kristeun]

Had this problem as well. turned out to be a faulty ECU, or maybe the MarkD chip in it.

[Rion]

Having the same problem, Seems my fuel cuts out, except I don't have to pull over I just tun the key off and back on and it "push starts its self" in 5th.. It does it on Hotter more Humid days I have noticed. Hasn't left me stranded yet, but (knock on wood) I'd like to get the problem sorted out. The fuel pump is new as are the pulse sensors which went out months ago. Timing Belt, water pump, Tune up all in the last 3 months.

I'm going to try the fuel pump relay first, Then I am lost after that.

[BlUe E30]

hey so im having this problem also i was wondering if you ever figured it out?

[ubernasty]

Now that's a better description of the problem than in your original post. Based on the latest post I'd add the fuel pump and/or relay to list of suspects.

that still doesn't answer the mind-boggling question of why it only happens when its really hot out however... so frustrating. i drove about 75 miles today w/o any problems whatsoever, and it was 80 degrees all day. (having problems with 90 degrees + days. and the car is not overheating btw)

i'm about to offer a paypal reward to whoever can provide correct diagnosis to this. :D

[jlevie]

Now that's a better description of the problem than in your original post. Based on the latest post I'd add the fuel pump and/or relay to list of suspects.

[ubernasty]

^^ would that only happen when its really hot out though but run perfectly fine any other times at night or mild- cold days?

seems like that may make the wiring super hot in the engine bay, making them softer and more flexible which could make the connections more susceptible to becomes loose. but that doesn't really seem what's going on. the car just stalls out under acceleration, pull over for a few minutes... starts right back up, drives fine for a minute or two then does the same thing. (the longer i let it sit, the longer it will go before cutting out again)

-thanks for the help btw

nick