91 SR5 pu has no power at all

[NORTON12]

I purchased this 91 SR5 3.0 V6 and I knew it had an engine issue. But after 2 weeks of trouble shooting I am getting no where. Hope someone can help with more knowledge.
Here are the symptoms -
1. starts up ok - chokes a little
2. when revving up in neutral it is slightly hesitant but not bad
3. put it in gear and I have absolutely NO POWER - it sputters and backfires in the engine, . If you floor it - you get basically no response.
You can get it up to 4th gear if you have a lot of patience.
4. 1st and 2nd gear will sputter until it hits 3500 RPM and then you have good power.
5. Hit 3rd gear and you can barely get it to climb in between backfires.

So far I have done the following:
1. Attempted to adjust timing at the coil
2. pulled all plugs and cleaned
3. found fuel filter to be on backwards - switched it and no difference
4. pulled fuel pump and replaced. (also checked for continuity thru the wires and all ok)
5. replaced all plug wires
6. and again tried to adjust the coil , sometimes gets better but no where near drivable.
7. I pulled the harness off the throttle body and it did not improve - just got worse -so I would say it works
8. Replaced intake valve (by front left corner) with another one and it only improved the suction sound from the engine.

don't know what else to do.

Hope some one can help me.
thanks

[Kyle4130]

those things are known for the head gaskets blowing. have you checked the fluids in that thing? whats the fluid in the radiator look like?

[NORTON12]

Thanks for your help but I did finally get to the source. The fuel injectors were clogged so bad that they had to be scraped out with a knife. I could have used a spoon though. After it was back together it ran better but still had hesitation and backfiring. I researched on the interenet and found a site that mentioned backfiring and it kept pointing to the TPS sensor. So I took it off and found that the bottom screw was loose and it appeared to be out of position. These things are very sensitive. But they are very easy to adjust while the engine is running. A simple ear to the Mass Air and a hand on the TPS solved my dilimma. It is a 17year old engine and sounds like its brand new with a tonne of power.

thanks for the help.