here's the problem. today car started acting strange... once started, will surge up to about 1700 rpm and hang between there and 2000 rpm. once in drive it will drop to around 1000rpm. throttle is in closed position, and idle screw position has not changed or been damaged in any way. i was stuck in town when this occured, so i tried to screw with it and i wiggled the maf plug and it dropped to 500rpm, then back to 700.

at this point, the whole operation problem changed. now it ran at the appropriate idle in park, but when the throttle was opened, it would just hesitate and sputter, to the point where it would backfire through the plenum and stall. the fuel pressure is at the correct settings (according to gauge) , and everything else is the same as before.

it has since returned to the previous operating scenario, with the high idle and drive rpm. i am at a complete loss here, as this makes no sense to me. how the hell could it idle that high with the throttle closed?? and, to make it that much more convenient, there are no codes from the ecm. please help, anything would be greatly appreciated. thanks!

 

2 immediate possibilities.
MAF...Disconnect the MAF and see if the problem goes away.
TPS, a bad TPS will cause huge RPM surges and may or may not throw a code.

 

it has a new tps. i will try the maf disconnect and see what happens.

 

check for a vacuum leak. my car did the same thing. high idle around 1500 in park and not much less in drive. turns out i had a hole in one of my vacuum lines. fixed it and idle went right down.

 

this is thunder85

i thought that might be the case, so i checked all vaccum lines, and pulled the main line while it was running to see what happened. it surged even higher. i am at a loss. could this be caused by the idle air thing? i just don't see how it can surge that high without the butterflies being opened.

 

it should surge higher. if theres a vacuum leak, the engine will up the rpms to try and make up for the lack of vacuum.

yes, the idle air control (IAC) valve could need adjusting. theres a tech article on this site that shows you how to do just that.