3.1 high idle, need help

[Carlspike]

Sorry, this is gonna be long. I just bought a 1996 lumina with a 3.1 and i've had a few problems with it. A few weeks ago it was starting hard or stalling when it was put into gear right after startup. After it stalled it wouldn't start back up again unless i pressed the pedal all the way to the floor (GM's clear flood mode.) Then it would start right up and run fine. It seemed like it was getting too much fuel on startup. I checked the codes and it had an EGR code so I cleaned the valve and I also checked the sensor readings on the scan tool and cleared the codes. After that it started hard 1 more time and that was it. Since then I have changed 1 plug wire (it was not correct for the car) put a set of platinum plugs in it and changed the air filter. I'm unsure if this is related to my high idle problem or not. My car always idles at 2000 rpms, hot or cold. I believe it's been doing this the whole time but not until I didn't really notice until I got under the hood to do the tune up. I am still pulling an EGR code (EGR system performance) and EVAP code (EVAP flow during non purge) and a high idle code. The guy who had the car before me said it idled high before the EGR valve went bad and after the cleaning it seems to be working properly, and I'm unsure if the EVAP system could mess with my idle. I checked my vacum lines about 12 times now and sprayed them and the intake and throttle body gasket with carb clean and nothing has happened. I have vacum all the way from the PCV valve to 1 side of the purge solenoid but nothing out the other side, I'm not sure if this is normal or not. I monitored the sensors on a scan tool and O2 sensor looks fine, as do the MAP and MAF and TPS. My IAC is 0 idleing (at 2000 rpm) but when I rev the engine up to about 4000 and let it come back down the IAC goes up to 34 as the engine gets down to about 1200 and goes back to 0 as the engine goes back to 2000 rpms. I'm not sure if this is normal or not. I know the IAC should be higher at idle but the car is already at 2000 so i'm guessing the IAC isn't needed at that point. I even went into the scan tool and changed the desired idle speed to 625 rpms and it only went down little bit. I have no idea what else to do to this thing, I don't just want to throw parts at it but I dunno how to figure it out. I'm not sure if even the ECM could be going bad. Sorry this was so long, thanks for any help anybody can give.

[bszopi]

RE: 3.1 high idle, need help

Just for fun, try hitting the ECM and see if it changes anything. Nothing hard (don't bring out the baseball bat), just tap on the top of it like you'd knock on someone's door. Its one way to check to see if the ECM could possibly be a culprit.

One other thing to check is the throttle plate. It just may not be closing all the way.

[eliteweapons]

You might want to check around the injectors too one might have popped an o-ring. Its rare but has happened. And since the car is new to you someone may have done a little rigging in there. Remember on a new used car you never know what you will find.

[Carlspike]

Well, tonight I changed the IAC and cleaned the throttle body and IAC passages. Then I did an idle relearn and it runs great, except for now my oil light turns at idle after my car is warmed up. I hope my sending unit is messed up and not not my bearings. I don't hear any top engine noise when the oil light is on so I think it's ok. Thanks for your help, I'm glad the idle is fixed now.

[Juglenaut]

Is the Engine temp sensor working right? Map and TPS are intercorrelated. IAC is effected by MAF mostly, but aren't electrically connected, they are however electronically interpoled.

EGR is effected by heated O2, Canister Purge Valve, and MAF

Check the Purge valve, the MAF, then lastly the EGR...Also one more thing check the catalyst monitor it can screw things up to.

The most simple thing that it could be is a Canister Vac diagnostic switch that could have stuck closed.

Seeing now I missed out, but you never know if it was intermittent, if it comes back test em'''.

It is possible by cleaning it up, then it cleared up some slack in the ECM for compensation....

[TheProfessor]

far as the oil light coming on
go under the car and check to see if the connectors to the oil sender in the pan are good
i had the oil light coming on and thats all it was
just the connectors