Hesitation

engines
pontiac

#1

MY 87 PONTIAC GRAND AM W/V-6 3.0 ENGINE HESITATES TREMENDOUSLY IF I ATTEMPT TO EASE AWAY SLOWLY FROM A STOP. THE SAME IS TRUE IF I’VE SLOWED DOWN TO A VERY SLOW SPEED AND ATTEMPT TO FEATHER THE GAS PEDAL. HOWEVER THIS DOESN’T HAPPEN IF I GIVE A STRONG PUSH ON GAS. AND THERE IS KNOW PROBLEMS AT HIGH SPEED OR DURING STRONG OR STEADY ACCELERATION. NEW PLUGS HAVE BEEN ADDED AS WELL AS WIRES. COIL PACKS AND IGNITION MODULE HAVE BEEN REPLACED AS WELL AS FUEL PUMP AND REGULATOR (FUEL PRESSURE) REPLACED. OXYGEN SENSOR AND EGR VALVE WERE REPLACED IN LAST 3 YEARS DUE TO SERVICE ENGINE SOON LITE.


#2

Try a bottle or two of Techron. Clean the throttle and MAF sensor. Check out the PCV system. Get a compression test.


#3

The throttle plate goes to the idle position anytime you take your foot off the gas pedal. At idle, the idle air control valve adds more air, and the engine computer demands more injected fuel, when the engine computer gets the word from the throttle position sensor (tps) that the throttle has moved. If the tps doesn’t send the right message to the engine computer, the fuel boost won’t happen. A dirty idle air control valve, and dirty throttle body bore and throttle plate, reduce air flow into the engine intake, which reduces performance at, and off, idle.
The idle air control valve and the throttle position sensor can be checked using the instructions in the repair manual.