My uncles 2000 Impala with a 3.4 stated to idle a little high. He changed the plugs, wires, PCV valve, idle control valve, and air filter. Plugs wire definitly in need of changing. While he had it apart i checked the throttle body and EGR ports. EGR was good bit throttle body and some oil on it so i wiped it out with a towel and throttle body cleaner. I then cleaned the MAF sensor. The car still idles a bit high but now when you are cruising and go to pass someone the transmission doesn't down shift even at WOT. The car has around 90,000 on it. Any ideas? The intake gaskets and radiator where changed at 65,000.

 

you could have a couple of things going on here, especially after all the work that was done. The high idle could be due be due to vacuum leak, a cracked vacuum line, or a bad/misadjusted idle air control valve. As for the downshift, isn't that controlled by a cable that clips to the throttle body? Did anything slip out of place?

 

W drove the car an hour to celibate the Independance Day with other family and we went to leave the car was idling real high. Had to be over 3000 rpm and it would drive 65 without touching the throttle. Didn't have my laptop with me so we drive it back and connected laptop. We shut ot off then we got to the house and when we started it back up it idled at 1500 according to auto enginuity. It has codes p0122 and p1122. Today i am going to monitor throttle position while shacking the wiring check voltages at tps. It that checks out then I'm going to change TPS and perform idle relearn.

 

Changed the tps and performed the idle relearn and it has been running good since.