Bouncing idle,high rpm on cold start and now check engine light?

MY 97 xj three morning ago, I started it up like always and it revved up to 2200 rpm or so and wouldn't idle down even with me maunally messing with the throttle arm on the intake. Now when it gets warm it will idle at stop by bounching around 200-300 rpm. Just a constant vroom vroom vroom type of deal. The check engine light came on yesterday so I am thinking a sensor but which one? Have any of you had this problem? map sensor? Thanks for any input

The most likely culprits are a dirty/sticking IAC motor or a malfunctioning TPS. Remove the IAC motor from the TB and clean it thoroughly. You can also check the output voltage from the TPS by backprobing the middle wire with the ignition on/engine off. It should ramp up steadily as you gradually open the throttle from 0.7-0.8v with throttle closed to 3.7-3.8v with throttle wide open.

Ok, cool. I have somewhere to start now. I didn't even think about it but I just cleaned and oiled my k&n filter so that may have something ot do with it. Hopefully it simple. Thanks alot

Check the codes for the place to start. You may have a bad temp. sensor.

what does it cost to have a dealer do that? Thanks

Rem870XJ said:

what does it cost to have a dealer do that? Thanks

Click to expand...

Probably too much, which is why they're called stealerships and why you need a tube of KY Jelly (to lube the anatomical part where the sun never shines ) every time you go there to buy parts.
Here's a free alternative:

http://www.allpar.com/fix/codes.html

I've got a listing of codes (I think I upped that...) on my site as well, in the Tech Archive section.

Have you checked for a vacuum leak, tho? The symptoms you describe often come back to that, and inline sixes are notorious for manifolds loosening over time (I just automatically get in the habit of retorquing my bolts once a year - I usually find one or two loose.)

Since you have a 1997, you're OBD-II. Therefore, you'll also want to look into an OBD-II "Code Reader" - should be in the $150-200 range. Eventually, it's cheaper to just get your own - I think it pays for itself about the third time you have the codes pulled. You'll be wanting a version that talks to Chrysler - but most scanners have "Big 3" compatibility anyhow.

5-90

checked throttle sensor and it shows an open. Middle wire was at 1.5V at closed throttle and 8.0V at wide open. Can my truck still run with numbers like that because it stopped doing all this crazyness three days ago. ???

id still replace the tps. mine was all funky for a month or so. would idle high at startup, then would cut out and die sometimes, or idle from 800 down to 200 then up to 1500. it would stop for a couple days then come back. dont think the demons gone. better to be safe then sorry.