idle hunting and oil cap 3.2l

[doppel]

I have recently begun having a bit of an idle problem after my 3.2l is warmed up. It begins to hunt for idle, up and down, rarely stalling. After searching the forums I set out to check the usual suspects (vacuum leaks, ICV and O2 sensor). The very first thing I tried was to remove the oil cap and when I did this, the idle smoothed out. From the what I have read, I expected it to drop if there was a vacuum leak, can anyone explain this?

Does this indicate that there is likely a vacuum leak?

[DRACO A5OG]

When hunting, tap on the icv with a screw driver, if it clears up you need to remove the icv and clean it. Also check the ohms.

[rusnak]

I think that makes a lot of sense anyway, especially at tune-up time.

You might check the fuel pressure regulator and pressure dampener to make sure that the vacuum hoses are attached. Other than than, it's time to make the rounds (fuel pressure, idle position switch, fuel air baseline setting, etc).

[stlrj]

Originally Posted by doppel

I have recently begun having a bit of an idle problem after my 3.2l is warmed up. It begins to hunt for idle, up and down, rarely stalling. After searching the forums I set out to check the usual suspects (vacuum leaks, ICV and O2 sensor). The very first thing I tried was to remove the oil cap and when I did this, the idle smoothed out. From the what I have read, I expected it to drop if there was a vacuum leak, can anyone explain this?

Does this indicate that there is likely a vacuum leak?

Not a vacuum leak indication since the removal of the oil cap introduced un-metered air which stabilized the idle, indicates a rich mixture. The hunting idle is a common symptom of a mixture being too rich.


Cheers,

Joe

[doppel]

Where would one start if the idle became too rich?

I can rule the vacuum leak out myself. I did tap on the IVC (no change) but did not do a cleaning.

Could a failing O2 sensor lead to a rich mixture?

Cheers,
Scott

[DRACO A5OG]

After she is warmed up, disconnect the 02Sensor, if she clear up then it may be faulty, if not then check your base idle setting by jumpering B&C in the engine bay.

If stock, base idle should be at 780 RPMs ( 84 & 85 ) and if chipped 880 RPMs, remember tach starts at 200 rpms then 400, 600, 800 and 1000 ...

[Joe Bob]

If you have an exhaust analyzer....it could tell you if there a lean hunt when warm.....02 or vacuum leak....even with the cap off.

[E Sully]

Check the CHT sensor.