M20 slow RPM drop +

[jasonbk]

Hey guys, for few days I've noticed the RPM drops slower than usual when I release the throttle. It takes longer to get to idle and it would idle higher than usual (900 rpm vs. 650-700rpm normally).

It happens randomly and it makes shifting really annoying - could be a vacuum leak?

[ahlem]

What do your throttle cable and cruise control cables look like? Maybe some white lithium grease is needed at the pivot points on your throttle body. You have an Idle Control Valve on the car? Maybe it needs cleaning. Could be a coolant temp sensor needs testing.

[modernist]

^ this, and it's normal behavior for it to drop to 900 and then slowly to your normal idle speed.

[jasonbk]

Just tested throttle cable and it's turns good as normal(I don't have cruise control).

I'll try to clean up the ICV and go from there. The weird thing is - when this symptom happens(slow RPM drop upon releasing throttle), the idle RPM would stay up at 900rpm at all time instead going back to 650 - 700.

[jasonbk]

Just noticed my crankcase vent hose was leaking (I didn't put the clamp around it) - I'm gonna clean it up a bit and put it back with clamp see if it fixes the issue.

[modernist]

Also check to see if your TPS is adjusted/functioning as it should

[jasonbk]

So.. I did tighten up the crankcase vent hose and it seemed fine for few days.
However I noticed leaking oil from one of the valve cover nuts (one that sit closest from crankcase hose).
Weird RPM drop issue would only come up when the car is restarted after running for a while..and this time RPM bounces from 1000 - 1200 in idle.
Once the car gets cold, it's totally fine again.

I redid my valve cover gasket about 5 months ago - do you guys think that I should replace the gasket again?

[modernist]

Did you check your TPS adjustment? Listen for a click right when you open the throttle. Do it cold and do it hot. If it doesn't click in either situation, it needs to be adjusted.