very annoying idle problem I've tried everything

[monkeydude3]

Hello all~

1994 XL here 4.0L OHV. Idle problem. When I first fire it up, it idles at 1500 rpm or so when it's cold, and gradually kicks down. When the temp gauge is still reading very low on normal (warming up) the idle eventually gets down to about 650 or 700 rpm. Which is perfect. However, as it heats up and gets close to warm and the middle of normal ,it idles gradually closer to 900 or 950. Isn't the idle supposed to go gradually down as it warms up??? I've put in a new IAC, lower intake gaskets (yes done perfectly no problems) Replaced any vacuum line suspected to be bad, plugs/wires, all EGR stuff (solenoid, valve, tube) fuel filter, air filter, cleaned the MAF.... I'm thinking my throttle position sensor, coolant temp sensor, OR air intake temp sensor (or a sick combination of these) is/are going bad in that they F up my idle but not enough to throw a code.... please anyone who's had a similar problem or has any ideas shoot them, I'll listen, thanks

George

 

[monkeydude3]

Also I want to make note I have a 5 speed manual transmission, so I suspect idle will be a little higher than an automatic, although it is still definitely screwy.

 

[MrShorty]

do you have access to a scanner? I'm pretty sure a '94 has the ability to output a live data stream to a scanner, which can then be reviewed to see if everything looks as it should. EEC-IV is not perfect at catching faults.

 

[monkeydude3]

not directly .... but eventually I can get it hoocked up to an ODIS snapon scanner which is a ton of computers in one.... something is awry somewhere