Truck keeps running bad, but is normal after you turn if off...help
Mar 5, 2013 | 11:44 AM
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Truck keeps running bad, but is normal after you turn if off...help
Hi guys, I don't post here a lot, just a looker but I am having some issues with my truck and Id thought I would get some thoughts/opinions.
Truck is a 2002 Gmc Z71 Reg. cab, with a 5.3 and 4L60E (rebuilt 3 years ago)..
So, back in the fall I was driving on the highway about 70mph going uphill, I gave the truck some gas to get around somebody, and when it downshifted something weird happened (this is really hard to explain). After that, as I would push the accelerator down to give it gas there would be no throttle response for the longest time....I would keep pressing the pedal and it would sound like the engine was revving but the Tach. wasn't moving and I wasn't going anywhere. After pressing the pedal down a certain amount, the tach. would take a sudden jump up and it was like the truck would finally "shift" into gear and throw your head back into the seat.
BUT, after replacing the fuel pump, everything was fine...until 3 weeks ago, it started doing it again. Its like it gets bogged down, then all of the sudden it clears up, throws the tach. up to 3500rpm and shoots the truck forward. It does NOT accelerate at a constant, even pace (if that makes sense). However, if I shut the truck off for a few minutes then crank it back up, everything is fine...until the truck is running up hill under load & I give it a little gas, then it slips back into doing this same weird thing.
I know it sounds like a bunch of mumbo jumbo, and it is super hard for me explain, so go easy on me. Does anyone have any ideas that I should look into so I can fix it??? Its really a pain to drive when it does this. The fact that it goes back to normal after shutting it off, kinda makes me think its a computer/ECM issue?
(FYI...the Engine light is on...throwing a MAF code, a couple O2 codes, and an "evaporative emission system" code. Tried replacing the MAF sensor, but that didn't fix it.)
Any help would be greatly appreciated, if I can clear anything up I will. Tried to explain it the best I know how...thanks guys.
Truck is a 2002 Gmc Z71 Reg. cab, with a 5.3 and 4L60E (rebuilt 3 years ago)..
So, back in the fall I was driving on the highway about 70mph going uphill, I gave the truck some gas to get around somebody, and when it downshifted something weird happened (this is really hard to explain). After that, as I would push the accelerator down to give it gas there would be no throttle response for the longest time....I would keep pressing the pedal and it would sound like the engine was revving but the Tach. wasn't moving and I wasn't going anywhere. After pressing the pedal down a certain amount, the tach. would take a sudden jump up and it was like the truck would finally "shift" into gear and throw your head back into the seat.
BUT, after replacing the fuel pump, everything was fine...until 3 weeks ago, it started doing it again. Its like it gets bogged down, then all of the sudden it clears up, throws the tach. up to 3500rpm and shoots the truck forward. It does NOT accelerate at a constant, even pace (if that makes sense). However, if I shut the truck off for a few minutes then crank it back up, everything is fine...until the truck is running up hill under load & I give it a little gas, then it slips back into doing this same weird thing.
I know it sounds like a bunch of mumbo jumbo, and it is super hard for me explain, so go easy on me. Does anyone have any ideas that I should look into so I can fix it??? Its really a pain to drive when it does this. The fact that it goes back to normal after shutting it off, kinda makes me think its a computer/ECM issue?
(FYI...the Engine light is on...throwing a MAF code, a couple O2 codes, and an "evaporative emission system" code. Tried replacing the MAF sensor, but that didn't fix it.)
Any help would be greatly appreciated, if I can clear anything up I will. Tried to explain it the best I know how...thanks guys.
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