Hey guys, New to the forum. I have a 03 completely stock GT. I bought this car back in March and its always had a stumbling issue. Mainly like backing out of a drive it will have an erratic idle and shut off. I also feel it surging while in overdrive with very little fuel demand. {Automatic Trans}I have replaced the TPS and the MAF sensor and no change. Id love some new ideas.... Thanks for the help

 

Hm....how many miles are on the car? Have you done routine maintenance things like replacing the fuel filter?

 

Almost 70k on it. No SES light and no stored codes in the computer. I replaced the fuel filter and cleaned the injectors. Its fine on acceleration, it does this only with very low fuel demand.

 

How about the spark plugs?

 

Have not changed the plugs. It doesnt feel like a ignition miss but I guess it could be.

 

I think your two problems are unrelated. But the idle problem sounds like a bad IAC Valve (Idle Air Control Valve). Get a can of carburetor or fuel injector cleaner, remove the IAC Valve (should be on the air intake somewhere) and give it a good cleaning, let it dry for a couple hours and re-install. If that doesn't work, then it may need to be replaced. Not that expensive and most auto parts stores should carry it. Good luck...

 

Ive already swapped the IAC and still does the same thing. My father in law took a look at it the other night and I couldnt get it to do it outside of the car. I got it in it and put my foot on the brake and got it to do it. Now I am wondering if I have some kind of vacuum issue.....

 

When you changed the IAC, did you also clean out the air passages in the throttle body that the IAC valve controls? If they are clogged up, you'll get weird behavior too. However, a vacuum leak, down stream of the IAC valve, can also cause this problem. Good luck...

 

Is the check engine light on? If so run a scan. BTW love the fact that its totally stock!

 

Yes I cleaned it out as well. Check engine light is not on and never has since I've had it. Does this engine have a MAP sensor? If so does anyone know where its located? Thanks for all the help guys!!