Another M42 Rough Idle Problem

[djchester]

Hi there. I have a 1995 318ti M42 with 328,000km. The idle has never been perfect on this car but in the last few months it seems to have gotten worse to the point where it will almost stall when it is warm.

I've read as many forum posts as I can and tried testing/replacing many items to no avail. I turn to you folks for advice on what to check next. I am going to try and post a video to help show the symptoms.

The idle is rough right from a cold start, however it seems to get worse as it warms up. Once it is warm, it will drop to under 500 rpm and almost stall, then kick up to 1200 rpm to keep itself running, level off at 800 rpm for a second or 2 then start dropping and repeat.

If I hold the throttle steady in neutral under 2000 rpm I can feel the engine shudder. Above that it seems smooth I think. It seems to drive smooth otherwise however it feels like it is lacking power.

I have replaced/checked/cleaned the following:
- New Head Gasket (upper and lower timing chain cover gasket as well)
- New Spark plugs/wires
- New ICV
- New O2 Sensor
- New knock sensors
- New CPS
- New Coolant temp sensor
- Replaced the big vacuum hoses (ICV to and from, valve cover to CCV)
- Cleaned the MAF (as much as you can with the barn door style)
- Replaced check valve and grommet for brake booster
- Checked the 'spider' hoses going to the injectors.

I've tried disconnecting the line from the CCV to the valve cover at the valve cover and plugging the hose to test the CCV with no change. I've sprayed throttle body cleaner on every hose to try and hear a vacuum leak. I am hoping to try and set up some kind of smoke test to test again for vacuum leaks.

It does smell like it is running rich. Also, the engine/exhaust sound goes from a chug, chug, chug, to a bupada, bupada, bupada, then back to a chug, chug, chug (this is why I need to upload a video ) Please let me know if there is more information that I can supply to help diagnose. Thanks! Chad