TheMurse

@larrytrk Gas and oil filler caps secured. Of note I did not experience this issue on Saturday morning when it was quite warm here. I've picked up a can of MAF cleaner and I'll attack that and the throttle plate later tonight, once I have a cold start I'll report back with my findings.

larrytrk

Just figured the easiest cause possible, I had work done and when I went to leave the idle was rough and it turned out to be a loose oil cap, settled right down.
good luck with the MAF cleaning!

TheMurse

Update:

Removed the cold air elbow and air box yesterday, applied MAF cleaner to the sensor and tidied up the throttle plate. Some soot had deposited around the edge of the plate but I didn't see any significant oil in the plenum. Buttoned everything back up, gave her a half hour to sit and then started her for the day.

The MAF and throttle cleaning has made no difference in the car's idle prior to completing the cat warm-up cycle. The idle remains rough and the random cylinder misfire codes persist. Once the car was up to temperature I did a quick sprint through the gears and felt no sluggishness in the engine and at idle the car is very smooth and quiet.

If I understand correctly the next step is to investigate a possible vacuum leak and consider replacing the AOS. Does the hive mind concur?

Petza914

With you seeing no oil in the intake, I would put a manometer on the oil filler neck and see what the vacuum reading is before going to that trouble and expense. You don't have symptoms of a failed AOS. A vacuum leak seems more likely, so smoke test the intake.

TheMurse

Diagnosis update:

While I'm waiting for delivery of my shiny new manometer I toyed with the MAF sensor. I disconnected the harness and ran started the car yesterday. The idle was a little rough, although not quite as noticeable as before and the ECU immediately threw a P1090 code. At the instant I cleared the code the idle smoothed, the car settled in at 750+/- RPM and ran normally throughout the rest of the day (although the P1090 code would pop with each start-up).

From this evidence does it look like I should order a new MAF sensor?

NevilleNobody

I honestly don't know as i am not a technical guy. My symptoms were a surging idle, so different to your symptoms. However, once the MAF was replaced, boom, ran like new.

Petza914

Yes.

DC911S

O2 sensors. Yours are old and they don’t last forever.