IronTom

Hi Guys,

Jeep Cherokee 1997, 4.0, Auto.

I have some problems with my Cherokee. I did check the standard culprits like the IAC motor. No change.

I think all of those might have one root cause and its driving me nuts:

1. 10-11 mpg highway, stock wheels. Very conservative driving
2. Slight RPM fluctuations (the needle barely moves). Sometimes it runs almost steady, sometimes I can feel a clear, random vibration. It seems to get worse when the engine is hotter. Can't detect it when not in idle.
3. RPMs drop low when shifting from D to N, but not always.
4. RPMs drop low when I floor it, sometimes.
5. The Evap Solenoid is noisy. It ticks very loud, easily heard over the engine running.

So I unplugged the solenoid to see what happens when its unplugged. I got a code 31 on the self-test (ignition 3x on-off-on), the engine kept runnin as above, but the vibration was a little worse and the RPM drop happened randomly now when idle.

I read somewhere that the EVAP gives input to the engine and that gas/air might be adjusted based on that data. If so, a bad EVAP solenoid might be my problem? Should it be as loud as it is now?

This is the part that makes the noise:

IronTom

Oh, and I did check for vacuum leaks, can't find any, thats why I am thinking it might be the EVAP.