Loss of acceleration at speed

[g.ruff561]

Here's the deal. On the road at about 70 mph. No idle problems, no electrical problems. Nothing suspect. Accelerator drops to the floor. No gas , no rev, nothing. Everything has electric power. Car coasts to a stop. I popped the hood to check for broken belts. Any smells nothing.

10 minutes later, turned the key. Vroom. All the way home no problems. WTF! When I got home I checked under the hood again. I checked under body. No fuel leaks . Alternator at 13.3. ?????

Any help would be appreciated. Thanks team........G.

[mike.bmw]

I'd suspect a loose battery connection or a loose ground.

[g.ruff561]

I'm thinking maybe pump relays. Keep in mind all electronics worked. Pre set radio stations and 6 button OBC never missed a beat. This is a car I just got one year ago this month so I have done suspension, brakes, belts, ac, oem maf, alternator bushings, Optima yellow top, Alpine HU, steering wheel swap, z3 antenna, all under intake hoses, Ryan G splitter. Car runs like a top. Now this!!

[unixnerd]

I'd agree with the comment about relays, fit new Motronic and fuel pump relays. I once temporarily fixed a dead E30 just by thumping it's fuel pump relay with my Leatherman.

[mike.bmw]

I'm thinking maybe pump relays. Keep in mind all electronics worked. Pre set radio stations and 6 button OBC never missed a beat. This is a car I just got one year ago this month so I have done suspension, brakes, belts, ac, oem maf, alternator bushings, Optima yellow top, Alpine HU, steering wheel swap, z3 antenna, all under intake hoses, Ryan G splitter. Car runs like a top. Now this!!

Ahhh, I missed the part about everything electronic working. Disregard what I said earlier about grounds/battery connections.

[g.ruff561]

No worries Mike. Anybody have a pic of the pump / ECU relay location. This is my first M42. The engine bay set up is different. I will check real oem for relay part # and cost. Thanks for the feedback. G.

[sketchkid]

I'll take pic tomorrow for ya I have to check mine tomorrow


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[g.ruff561]

@ stretchkid, good looking out. I'll be checking. It's funny, I checked YouTube and there is not much there for E30 M42 general maintenance. Lots of turbo stuff.

[ForcedFirebird]

You have to remove the harness cover.


They are on the driver side. Same part #'s as an m20 (Replacement relay is part Part # 61368373700), usually orange, four prong. The white/silver five prong is your main relay for the ECU...

[g.ruff561]

I might as well replace all 3 since I'm right there. Thanks for the feed back...... G.

[ForcedFirebird]

Main relay is part # 61361729004

Other 2 are the same (one is fuel pump, other is oxygen sensor).

[TobyB]

After that, which you should do first,
the other things would be fuel pickup screen, filter
and pump, especially if there's crap in the tank.

t