1986 735i - Intermittant rough start, dying at idle and loss of power.

First Post! Been lurking for a while but thought I would see if anyone on this forum can lead me in the right direction with my beamer. Not very mechanically inclined.

1986 735i with 140,000 miles.

Runs/drives and starts up ok most of the time but has a intermittant problem which is keeping it from being my daily driver.

Starts up 90% of the time first try but occasionally takes several cranks before it fires or sometimes will not start up at all. Then fires up first try the next day.

Occasionally dies when idling at stops or when slowing down.

Occasionally loses power when driving. Will have my foot on the gas and suddenly lose power (gas) for a few seconds.

Will go a day or 2 with no problems at all then have day where it has all these problems. Been driving it with these issues for about 6 months.

It really seems like a fuel system problem. Have replaced the Fuel pump, fuel filter, air filter, fuel pump relay and spark plugs. None of these have made much of a difference.

Any ideas?? Any help would be much appreciated. Stressfull driving this thing in traffic. Thanks

Here is a place to start reading http://www.e38.org/e23/

Not a lot of older 7 posters on here. Mostly just those who have a problem.

i would start by checking the crank signal when it acts up. they can be goofy sometimes and create a lot of driveability issues.


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I had the same issues in my 87 535i with the same engine. I thought it was the MAF, but it ended up being the ECU.
There is a single solder joint that gets corrosion and cuts off the fuel.
I bought a second hand ECU at a yard, and never had the issue again.
There are posts that talk about resoldering the trouble point, but I didn't have success at it. Apparently it's a common problem.
Let us know what happens.
Good luck.