Engine cuts out in mornings at same spot...

[muppet]

This only happens about half the time, and its only in the mornings but after the car has reached normal operating temp. I start the car, idle for a few minutes then drive a mile before getting on the freeway. After a mile or so of freeway the engine will randomly cut, like its hitting a rev limiter but cuts harder and it doesnt matter what the rpm is. Sometimes it clears up after a bit or when I get off the freeway 3 miles later. Last week the CEL came on(but this was one of the mornings it didnt cut) and threw an o2 sensor code. I replaced that, but no change. Maybe a fuel pump? but it never happens any other time or on weekends when I dont have to make that drive. Oh, and its a 90 525i with m20 engine. 5spd.

[jlevie]

The odds are that the engine did need an O2 sensor as the useful life of that sensor is not more than 100k. But in all probability that fault code was the result of an intake leak. the definitive test for intake leaks is to have a smoke test run on the intake.

That said, it sounds like you have other problems that are causing the cut out. if the fuel system is to blame you'll probably see the econometer drive towards zero just prior to or during an event. The cause of that could be a dying fuel pump or flaky fuel pump relay. A clogged filter would not tend to cause an intermittent problem and rather would cause a continuous problem. Running the fuel system tests in the Bently manual should tell if you have a fuel system problem.

Other possibilities include a flaky main relay, flaky CPS, bad coil, flaky fuseable link, or even a flaky DME.

[muppet]

The odds are that the engine did need an O2 sensor as the useful life of that sensor is not more than 100k. But in all probability that fault code was the result of an intake leak. the definitive test for intake leaks is to have a smoke test run on the intake.

That said, it sounds like you have other problems that are causing the cut out. if the fuel system is to blame you'll probably see the econometer drive towards zero just prior to or during an event. The cause of that could be a dying fuel pump or flaky fuel pump relay. A clogged filter would not tend to cause an intermittent problem and rather would cause a continuous problem. Running the fuel system tests in the Bently manual should tell if you have a fuel system problem.

Other possibilities include a flaky main relay, flaky CPS, bad coil, flaky fuseable link, or even a flaky DME.

I agreee, the o2 sensor probably just gave up the ghost, but the fact that it did at the same time i was having this problem made me think, and hope it would be as easy as the car not going from open loop to close. I will test the fuel system and get back, but it doesnt seem like the usual failing fuel pump symptoms....

[Knockenwelle]

I had a bad ground cable at the battery (trunk-mounted) cause some mystery cutouts on the road. The car would just shut off, then come back fine.

[E30QC]

me too i have this problem, but it can occure up to three times on one stretch of highway, if i stay under 3grand, no prob. but exactly as described, just dies out, and today, when i cranked it over again to restart it, it fires back to life right away, always, it backfired.. i mean, do i need a new fuel filter? i know my icv needs changing because it alters between a steady 1k idle, to a pulsing in between 1000 to 1250,
p.s. i have an eta..
mike
also, sometimes, it just doesn't die, maybe its' my cheap intake filter, cone., or do you think its' an electrical issue, i've had the Engine Position Sensor, and flywheel replaced recently.