Unofficialbmw.com

[GregByrd]

My wife's 85 325e has two problems which may have either the same or different causes. The first problem, which is the more serious, is that while cruising from anywhere from 30-70 mph, the engine will stumble, sometimes to the point of bucking drastically. This usually happens when I have been accelerating, either during or right after hard acceleration. While on a long trip recently (1300 miles round trip) I seemed to be able to temporarily "cure" this problem by using 93 octane fuel from pumps that had dedicated hoses (not pumps that had one hose for all grades). The problem is occasional, and sometimes disappears for a week or two and sometimes plagues us for days at a time.
The second problem, which is annoying but livable, is that the idle is rough when cold but sometimes fluctuates (though less drastically) when warm and at idle.

In response to these problems and for other previous problems, I've replaced the following:
cap, rotor, wires, plugs (oem parts)
both fuel pumps (oem parts)
relevant sensors (temp sensor, thermo-time sensor)
o-ring seals on fuel injectors
air filter
fuel filter

Also checked the following:
vacuum hoses. All seem fine but there could be some leaking that I've missed.
big valve connected to intake box. the flap moves freely and I can hear it snap open and closed when I rev the motor.
Cold start injector. works as it's supposed to.

Any ideas?

Greg

[james hampton]

I own an 85 325e and when that happened to me I replaced the idle speed control module. It is located above the glove box. when the car started to buck I would push in the clutch and the rpm's would go all over the place.I believe that part will fix both problems.

[bhorsley]

I am having similar problems with my 1986 325. I am going to replace the ecu.

[bill84eta]

Hey Guys;

Try my penny trick first before you start throwing buck at it.

See my post at "Surging Idle & Jumpy Acc"

Later;
Bill