I have a 1996 chevy cheyenne C1500 with a 4.3L engine with 93,000 miles. I was driving and the check engine light came on and minutes later the car died. I can start the engine and it itles find but as soon as I press the gas pedal down it chokes, backfires and stalls. If I press the gas pedal down slowly it reves all the way up and I can hold it at that rmp. So, I assume the fule pump is ok. 6 months ago I replaced the spark plug wires and cap and rotor.
I changed the cap and rotor again because it was bad and the camshaft position sensor and that didn't work. Then I borrowed a computer and the codes said there was a problem with the MAP sensor. I replaced that and still no success. Then I changed the throttle position sensor and that didn't work.
I also changed the fuel filter. I erased the codes and the car runs fine at itle. I can rev it up extremely slowly but as soon as I press it down normally in park or drive it bucks, backfires and stalls.
I'm at a total loss on what it could be. Could it be the control module or MAF? The MAF looks clean and the wires are not broken. Please help.
Clean out the throttle body and also check air filters. Wouldnt hurt to do fuel pressure and volume test also to eliminate fuel pump
October, 19, 2007 AT 10:30 AM
Thanks for replying. I cleaned the throttle body and the air filter was changed about 6 months ago and it looks good.
Do you think it could be the fuel pump even though I can slowly press the gas pedal and rev the engine all the way up and it keeps going until I take my foot off it. Seems like it's getting fuel to sustain the high rpms. I don't have a fuel tester unfortunatly, car is stuck in driveway.
October, 19, 2007 AT 2:44 PM
Could be the MAP also. Now that I think of it it could be the Throttle position sensor. Your pretty much out of luck unless you have a testor or lots of money to check all of these things out. Buy some gd cleaner and spray the crap out of the map but dont touch it. If that dont work move on to the MAP and the TPS.
October, 22, 2007 AT 11:03 AM
This is what I replaced so far. Fuel filter, Cap, rotor, Cam Position Sensor(Pickup coil), spark plugs, wires, MAP sensor and TPS(throttle positon sensor).
Problem still exists. I rented a tester and it originally showed the MAP sensor was high so I replaced that and there are no error codes now but the problem still exists. I'm at a total loss now, and depressed. I might have to have it towed to a dealer. UGH.
October, 22, 2007 AT 8:36 PM
I mean MAF sorry. I would check the IAC also. Also the coolant temp switch or sending unit may be bad causing improper mixture of fuel in the air. I would also test the Fuel Pump. I still would like the fuel pump to be checked at or the Fuel Pressure regulator.
October, 26, 2007 AT 7:44 AM
I believe this truck has a big hole in it in which I am pouring my money into.
I replaced the temperature sensor and IAC and still have the same problem. Then I went and cleaned the old MAF and that didn't work so I replaced the MAF and it still bogs down and back fires when pressing the accelerator. I bought a fuel pressure tester and I'm going to do that next. Where is the sending unit located?(1996 chevy cheyenne, c1500 4.3L)
October, 26, 2007 AT 4:47 PM
It is located on the fuel rail, where the injectors are plugged in.