Rough idle - Econo gauge

[mkovic]

Hi,

New to the forum, just got my first BMW a week ago. Been browsing throgh threads - very intersesting.

I have a problem that I can't quite diagnose. The car runs rough first off when cold. It seems like it wants to stall, sometimes it even does. In mean time, when the engine is haunting for idle the econo gague oscialtes from left to right violently. As soon as the RPM sattle at 1.100 or so the econo needle pegs all the way to the right (max fuel consumption). If I try to floor the acclerator during this the RPMs won't go any higher than 1.000 and there is gray smoke coming out the back. I't a M20 engine.

Any insight greatly apricated.

Thanks

[angrypancake]

at idle you're going to have max fuel consumption. whereas when you're moving and take your foot off the accelerator its going to go to minimum consumption.

1100 rpm seems a bit high, then again i don't know much about the m20. Idle Control Valve perhaps?

gray/blue smoke = burning oil.

so you're driving an early 525? can you fill out your profile for us? someone with more knowledge than me will be able to help more with as much info as you can. location, mileage, production date, auto/manual, etc etc.


welcome to the forum.

[Blitzkrieg Bob]

Clean the Idle control valve with some throttle body cleaner, make sure the valve inside is clean and free to rotate.

Ahhh... what the heck clean the throttle body too.

Check all the hoses to the manifold.

Check plug condition

Check the oil condition

Look around for the obvious loose wires, plugs etc.

Try a "stomp test" and bring up any codes ??? O2 sensor???
Since you have an M20, your car may not have the check engine bulb installed, so if the check engine light never worked..neither will the stomp test.

let us know what you find and what improves

[mkovic]

Thanks for the ideas. I will try them out this weekend and report back.
The car is actually a 518 with M20B20 engine transplant. It either doesn't have check engine light or it is not working.
Thanks again!

[mkovic]

I cleaned the idle control valve and the car ran fine at approximately 700 rpm for two days. Today, when I was leaving to go to work the car would start, run fine for a few seconds then stalled. Now it wouldn't start at all. I had it connected to jumper cables off of another car for a while and tested all the usual suspects: there is spark, fuel pump is running, fuel is flowing to the engine, the timing belt doesn't seem to be snapped. Is there any other obvious place I could check?

Thanks in advance for any ideas.

[E34-520iSE]

Dribbling fuel injectors/duff fuel pressure regulator? Both are common M20 gremlins. Is it trying to fire during cranking?

Cheers,

Shaun

[mkovic]

Yes, it does try to start during cranking, it almost catches but won't start. Drove me nuts all afternoon. :-)

[E34-520iSE]

Is it a manual? If so, tow-start it. The non-start thing may be a one-off.

HTH,

Shaun

[mkovic]

I managed to get it started. I still don't know what was wrong. After long time of cranking it started on it's own.
Thanks for the ideas.