hesitation after warmup

[johnsjeeps]

I am new and have a problem with my 93 GC 4.0 with 170000+miles...After driving about 5 minutes I start to get hesitation/jerking and at stoplights the RPMs drop from 1000 to below 500 for a couple seconds then go back up. It only seems to happen when it is warmed up. It has a new radiator, water pump, fuel filter, spark plugs and fresh oil all within 2 weeks which also is about how long i have had this prob.(this was the original prob-then antifreeze started spraying)...Anyone with ideas??? Thanks!

[Dale Aeppli]

Originally Posted by johnsjeeps

I am new and have a problem with my 93 GC 4.0 with 170000+miles...After driving about 5 minutes I start to get hesitation/jerking and at stoplights the RPMs drop from 1000 to below 500 for a couple seconds then go back up. It only seems to happen when it is warmed up. It has a new radiator, water pump, fuel filter, spark plugs and fresh oil all within 2 weeks which also is about how long i have had this prob.(this was the original prob-then antifreeze started spraying)...Anyone with ideas??? Thanks!

HI, YOU SAY THE PROBLEM STARTED AFTER THE ANTI-FREEZE SPRAYING, POSSIBLY THE ANTI-FREEZE SPRAYED ON THE THROTTLE POSITION SENSOR AND IS CAUSING IT TO SHORT OUT. THE THROTTLE POSITION SENSOR CONTROLS THE TRANS. AND TELLS THE ECM WEITHER THE ENGINE IS IDLING , UNDER LOAD AND OTHER SIGNALS. THAT WHATS CAUSING THE RPM. TO VARY, UP AND DOWN HPOE THIS IS OF HELP DALE [email protected]

[johnsjeeps]

That sounds right on actually but where do i need to look to see if that is shorting out? I know i should really have a Haynes(I will soon)....

[dksob81]

ok here is another one for ya, know this from experience. check back at the fuel filter, make sure there is absolutely no LEAK, I can't stress it enough.. my friend has a 91 Pontiac Sunbird GT, the car would warm up fine but as soon as it got to operating temp. it would idle really rough, and sometimes idle real low to the point that it would sound like it was gonna stall. we looked at it for 2 weeks just replacing lil things, Plugs, Wires, Coil Packs, Ignition Modules, Cleand the EGR Valve, O2 Sensor. and the next step was too change fuel filter got underneath smelt gas really bad, searched for a leak couldn't find one, then went to take the fuel filter off, and there it was a small leak in the Fuel Pump lines. YOU SAID U CHANGED FUEL FILTER AND THATS WHEN THIS PROBLEM STARTED, SO I WOULD LOOK THERE FIRST TURN THE KEY ON AND GET UNDERNEATH MAKE SURE THERE IS NO LEAK OR SMELL OF GAS, I AM WILLING TO BET THAT IS WHERE UR PROB IS....