[Skylour]

1999 chevy silverado 2wd 4.3l with 105,000 miles it hesitates on acceleration and seems to backfire. its done this for a few months and just started out of nowhere. To try to correct the issue I have changed spark plugs and wires, distributor cap and rotor, fuel pump, fuel filter, spider injector and also have cleaned the maf and have checked the throttle position sensor. the truck throws no codes at all. I am at a loss of thought maybe ignition coil or control module?

 

[xPosTech]

I would start by checking fuel pressure. Also check for vacuum leaks.

Ted

 

[Skylour]

We checked fuel pressure when key is turned it shoots up to 55psi then falls down instantly and while running it stays around 57psi

 

[j cat]

We checked fuel pressure when key is turned it shoots up to 55psi then falls down instantly and while running it stays around 57psi

key on engine off fuel goes to 55PSI then drops quickly ? if so the fuel pump has a bad check valve..

V6 IMO EOEO 60-65psi..

 

[Skylour]

I also ran the truck with a scantool running data stream and the trucks spark was around 20-23 idling and while driving it slowly increased and at one point reached around 40 then it dropped to around 16-19 and started sputtering then when it quit jumped back to around 33 I also had a misfire on cylinder 4,5,6 when it started sputtering then they quit and there wasnt any misfires after but sputtered again