surging Idle

[R&D man]

last night I started trouble shooting my surging idle...this is what I found.
when the car is cold the idle is 600rpm and once it is warm it surges
if i pinch the small line from the valve cover breather tube the idle seems to settle down to around 1000.

if I disconnect the tps the idle stays the same.I tried a diffenrt on and it does the same thing when actuated ( i plugged in a diffenrt one while the engine was running )

if I disconect the coolant temp sensor nothing happens.

if I disconnect the MAF sensor the engine quits.

if I diunsrew the oil cap nothing happens.

tonight I will pick up the valve cover gasket set and give that a try.
I dont want to change every sensor on the car just want to find the right solution for the surging idle.

any thoughts on what else to try.
other than a for sale sign on the car

[sharky]

stuck icv

[R&D man]

icv

I clean and checked the valve it works fine

[Dissembler]

in my experience, its your coolant temp sensor. with it disconnected, the computer will assume the engine is freezing and dump fuel so that it stays lit in attempt to warm it up. With out the coolant temp sensor there, the computer does not know the engine is getting warm.

depending on the car, having no ECT sensor will result in a no start or high idle/rich condition

I'd suggest you grab an ohm meter and a thermometer. check the resistance value of the ECT sensor vs temperature and compare it to whats specified for a known good sensor

[Adrian_Visser]

You have a vacuum leak somewhere, the fact that nothing happens when you remove the oil cap means that the engine is already compensating for it. Dead give away.

[Boosted E30]

Sounds like a vacume leak to me to.

Easiest way to find it get a can of brake cleaner and with the engine running spary everything section by section on the intake side, once the idle smooths out you found the leak.

[R&D man]

no change

So far I found a leak on the ICV hose and fixed that..I canged the coolant temp sensor and that just fixed the cold start idle but once the car warms up the Idle raisees to 1100 rpm and surges to 1300 and back down to 500 and repeats over and over.
I have gone all over with a propane torch and cant find anything else that is sucking in air.
One thing i notuced is the small hose underneath the large one that goes to the valve cover .
When you pinch it the idle gomes down to 1000 an stays steady.
I can still smell exaust that is strong smelling like it is running rich also the plugs are sooty.
what should i do here I have no means of diagnoses just propane and a prayer.

[Adrian_Visser]

Take it to a shop and get them to smoke test the intake system.

[R&D man]

smoke test

Well the car goes in on monday for a smoke test...hopefully the surging idle will go away......I am so close to giving my car my own smoke test(can of gas and a match.)