I have a 1989 Jeep Cherokee 4.0 AW4. I am noticing the RPM's going up to 1000 RPM's when shifter is in Park or Neutral. This happens after the vehicle has been running. At first crank in park the RPM's sit normal around 750 but once I shift from D back into Park or Neutral the RPM's go up to 1000 or slightly above every time and stays there. .. Is this normal?

I recently replaced the IAC with a Standard brand to help with a very low idle issue I had. It fixed my very low idle (almost felt like Jeep would stall idle was so low).

The higher idle in Park or Neutral doesn't really bother me too much but just curious if this is something the engineers intended purposely to happen when in Park or Neutral and if any other Renix owners have this issue. Was also thinking it could be something with my TPS or MAP sensor but this didn't happen until I put the IAC in.

Thanks for the help in advance~!

 

It's normal to idle 150 to 200 RPM higher in P or N. 1,000 sounds high to me.
It can be a slew of things and not necessarily needing parts.

check to see if your intake manifold bolts are snug.

Have you ever visited my website and completed Tips 1,3,4, and 5? I'd do those just cuz.

 

Thanks for the response. That makes me feel better. Also I'm not sure how accurate my RPM gauge really is so it may be that I'm actually in that range. I will also check the intake manifold bolts. Do you know what tool and what size I would need to do this?

 

9/16" wrench and socket. Some extensions. Easiest to do with the air box out.

Then, do the Tips.