BMW Headache

Late in on this one, but the oscillating idle on these engines is sometimes traced to failed VANOS seals. Beisan Systems makes replacement parts and has extensive DIY guidance on their site; BMW only offers the whole VANOS unit. I did the replacement on my M54 and resolved a cold idle oscillation. Unfortunately, doing the job on a single VANOS motor requires some special tools.

I'm not discounting a vacuum leak - these are all too common, and you won't find an oddball one without a smoke machine - but it sounds like you've been relatively thorough in this regard.

In reply to 02Pilot:

Renting a fuel pressure tester after work today to see what I get with that. Otherwise I will be doing a diy smoke machine in the near future.

Thanks

1,The engine seems to like a little air leak...this points to a stuck ICV in the closed position or, the air is needed due to #2.

2, The plugs are black, coupled with idle deteriorating as the engine warms up. This points to an excessively rich mixture. It may be worth it to check the engine coolant temp sensor resistance values at cold temp, and at operating temp then compare them with the values listed in the Bentley manual. Make sure that the wires serving the CTS are not damaged.

m

Checking both this evening! Thanks 7

Update:

Hey guys took a week off to regain sanity. In the meantime I built a DIY smoke tester (quite fun) and went ahead and checked the engine for vac leaks.

Well the smoke tester worked great! It also revealed 0 vacuum leaks unless I created them by popping a hose.

The CTS checked out, I have 2. Checked the IACV and it opens and closes to spec.

I was able to drive it for a day with a vac line pulled, about 45 minutes into the drive the problem started happening even with the vac leak.

I am really leaning toward an ECU problem (being that it got soaked) at this point and will likely snag one of the ebay.

Open to opinions/advice though.

Thanks GRM

Tried out new ECU, same problem. Looks like I will be pouring into some wiring here soon.

Update.

Pulled the engine side harness this evening. Found a few interesting things.

1. Knock sensors are both shot and falling apart
2. Burnt wiring in oil sensor and oxygen sensor pigtails

I replaced the effected wiring and will try to source some knock sensors. Hopefully one of these was the problem.

Thanks guys have a great weekend