Upon startup my '89 3.9L 4x4 idles at about 1500-2000 rpm and almost sounds like a diesel. It jumps up a little bit a couple times about 10 seconds in. Could this be a dirty IAC valve? If the idle needs to be adjusted, I could use a couple quick pointers.

I have also noticed the temperature does not go up at all on the gauge cluster. I mostly just drive the truck half an hour to work when the roads are bad here in SW OH, and sometimes after I finish a repair to make sure an issue is fixed. I have interior partially taken apart right now so I may check the connection for corrosion later.

Little bit of history on the truck: It was a farm truck in SE KY for a number of years, sat for 6 years and has been mine since 2020. No rust at all on the body but there was a lot on the frame due to dirt and moss sitting in there from farm use. I checked with a magnet months ago and the plenum gasket has been replaced and there was no oil in there.

I have downloaded a manual for a different year so I am able to reference pages from that if need be.

 

89 shouldn't have the plenum issue. Yours should be throttle body injection....

There is a one wire sensor for the temp gauge in the dash. Should be on the passenger side of the front coolant crossover in the intake.

Cleaning the IAC well sure won't hurt.

 

Thank you for your reply!