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So my truck is a ’98 GMC 1500, 2wd, 4.3 Vortec V6, 348,000 km, auto trans.
90% of the time, the truck runs great, except for what I believe is an unrelated issue, I’ll explain in a minute.
So once or twice a week, the truck won’t idle, and start hesitating, overall just running crappy. It seems to be mainly at the lower rpms, seems to clear around 3000 rpm. It usually lasts until it ends up stalling from the low idle which is usually pretty quick if I don’t notice it. It normally starts back up hard like it’s flooded, pedal to the floor helps. Once it starts tho and I give it a couple good revs, it runs just fine. That’s also without turning the key to off the off position. Check engine light came on once with a map sensor code.
So what I’ve done so far:
New map sensor, cleaned egr valve and made sure it wasn’t sticking, and cleaned the throttle body including the idle circuit.
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So I put my new fuel pump in today, and the truck runs perfect now. When I get on the gas hard it’ll downshift, rev, and accelerate, instead of studdering and slowing down.
I also believe I found the root of the problem with the evap system, when the pump last got replaced, the return and evap lines got switched, causing the evap to draw fuel from the bottom of the tank.So now is the first time I’ve been able to hammer on the gas of this truck since I bought it, and it’s got tons of power for a V6, great for pulling away from f-150’s and ram’s hehe
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