1999 BMW M Roadster check engine light help - BMW Forum

FNFLYIN90 · 10-17-2008, 03:03 PM

the vehicle: 1999 M roadster S52 with 24k miles
Today I got drove my car for the first time in a couple of weeks and noticed it now has a check engine light. Right away when I got got to work I ran a OBD2 scanner on it and found these codes:
P1250
P0300B
also had a couple more that were misfires on cylinders 3, 4, 5, 6.

Any ideas on what this could be?

The car drives fine except it has a rough idle, that is the only thing I have noticed different.
Thanks for the help ,what should I check/change on the fuel pressure regulator. Yesterday I took off the heat shield and had a look at, everything is connected fine and is very clean. Is there a circuit for the FPR that I can change maybe?

I had a tech friend look at it yesterday, he thought it was the crank case vent valve, so I replaced it last night and that still did not help.

The car seems to run perfectly fine when driving, but when at idle it really gets a lumpy idle and you can feel the engine shaking the car. It also smells like it is running rich. Anyone have any ideas?

marti5 · 10-18-2008, 03:00 AM

Crank shaft sensor or o2 sensor or MAF.

FNFLYIN90 · 10-20-2008, 09:16 AM

I figured out what was wrong Saturday. After looking over ever vacuum line and all sensors tested I finally started spraying brake cleaner on each different vacuum line to try to find a leak. Sure enough on the side of my throttle body there was a leak (when you spray break cleaner on a leak the idle will jump and lower). I went and bought a new profile gasket that connects the throttle body to the Intake manifold.

When I was in there changing the gasket the one I pulled off my car was perfect, no defects rubber circle gasket, them I noticed I had a long crack on my intake manifold where the throttle body connects. I switched out the intake manifold and right away the car drove perfect and CEL light went away.

Drove the car Sunday to an Autocross with SCCA at Route. 66 and had a blast the car drove wonderful, even though very slippery around every corner.
Thanks for the help.