gasouthernxj

So my 92 4.0 idles around 700 or so RPM, but upon acceleration the RPMs only go up to about 1250 or less at cruising speeds. The engine sounds normal, everything feels fine. Is there a sensor somewhere that could be busted? Why would it only not read right under accel/cruising?
I did have a little trouble with it stalling out at idle/hesitating at acceleration the other day, but that seems to happen when it sits for a day or two without being driven, and even then it's pretty rare. The RPM problem seems to have manifested since then.

Any ideas?

thatXJguy

I had an issue recently with my RPMs sitting at about 600.

I checked the motor with an OBD2 computer and found that there was an issue with one of my fuel injectors. I put some oil on the metal connectors and plugged it back in. Never had another problem since. I idle where it should be again.

I think the idle air controller is another common source of issues with RPMs.