318 rough idle and random CEL

[blatant]

So I have been daily driving a 95 318 (m42) for the past couple weeks. It idles roughly, bogs down under 3k, and smells like it is running rich.
The CEL only comes on when I keep the throttle position at a certain position for an extended period of time. The CEL will illuminate and then I can floor it and it will remain on, but if I left off completely it goes off. Once I'm on the highway and the car has been running for an extended period of time it acts normal. No longer bogs, but you can still smell the gas from the tail pipe when I get out of the car.

The code from the Peake reader is C9 which is lamda system (I believe).

My first reaction is to check the TPS, but I wanted to see if anyone else had any input.
The maf is good, new fuel pressure regulator, new intake boot, no vacuum leaks. Car is currently at 187k miles.

Any help would be appreciated!

[1996 328ti]

I had the same problem after disassembling and reassembling my intake.
I thought I was going to pass out from the gas fumes in my garage.

The next day I took it apart and reassembled and can only speculate that there was a gap between the upper and lower manifolds.

[blatant]

Just checked with the peake again. Only code present is the knock sensor code 3-4. Is it common for the sensor to go out? Looks like a pain to change!

[xxxJohnBoyxxx]

Knocks are a mild job to change. Bad knock sensor will cause the DME to retard your timing which causes bad mileage overly rich exhaust smell due to the spark coming way late on on the ignition stroke. I had one sensor go bad on my 97 318 and I lost a lot of power in the higher RPM past 3,000. The knock does a self diagnostic at start up and I think you have another issue then just a bad knock sensor. Maybe the TPS is going bad, test it and make sure it is linear from idle to wide open.

[blatant]

Thanks for the reply. I have ordered the knock sensor and will report back about the TPS.

I believe you are correct about the two underlying problems.

[jerrytheautodoctor]

curious as to whether or not you've had any successes with this issue.

[automaton]

I was wondering if you solved this problem also. I seem to have the same thing happening to mine, right down to the gas smell and the CEL coming on when holding the throttle in the same position for an extended period.

[1996 328ti]

Did this fix it?
I'm having a similar issue.
I'll start another thread.

[automaton]

I found the issue with mine. There was a split in the intake boot. The engine was drawing in all sorts of unmetered air.

I had looked it over pretty well and never saw the split, but I was taking the intake off to try cleaning the Idle Air Valve. When I was taking the boot off the front of it split. Upon further investigation, the back side had a split in one of the valleys. I wouldn't have found it if I didn't remove it.

I replaced the boot and all issues disappeared.