crossy's son

Well guys my dad and I have been fighting this truck of ours for the last 4-5 months and just can't figure it out, at 3/4 pedal up to WOT the truck falls FLAT on it's face, like dangerously, like to the point where it actually goes SLOWER at WOT then it does at 1/2 throttle or something. It used to pop out the TB when we first got it but that was when it had a bad injector......The truck absolutely runs 100% smooth at idle and up to a little before 3/4 pedal when you're driving it, then falls flat on it's face and dogs.....

oh and if it's in park or Neutral and you rev it up, it sounds great and doesn't stumble or anything, has great throttle response right up to 4500 rpm redline. The truck is a joy to drive around like accelerating normally becuase it has nice throttle response and the new trans shifts nicely and shifts kinda high in the RPM's which gets the truck moving.

Get read for the huge list of everything that is either brand new or has been swapped out with known good stuff off other trucks we have around....This was all done within the last few months and the truck sees no road time, it's a project that is done besides the fact that it runs $hitty.

The truck is a 94 K-1500 4x4 pickup, 305 tbi, 4L60E, 3.73 gears, 31" tires.

New-
-Spark Plugs- ACdelco
-Distributor Cap- ACdelco
-Rotor- ACdelco
-Spark plug wires- ACdelco
-Ignition module- Removed from a strong running 350 truck (mine)
-Coolant Temp. Sensor
-New Catalytic converter (high flow)
-New Dynomax high-flow 3" exhaust system
-Fuel filter
-In tank Fuel pump is brand new (did it yesterday & today, AC delco)
-Fuel Sending unit (all new sock and everything)
-The injectors and Pod are from my Dad's strong running 305tbi, THe fuel pressure regulator is rebuilt (new diaghram), injectors have new filters and stuff. They run perfect on his 87 in my signature.....
- Every single vacuum line under the hood has been replaced with new lines by me...
-Ultimate TBI modifications to the TBI unit
-throttle body spacer
- New air filter and higher flowing intake tube
- Seafoamed engine through vacuum hose from brake booster,
- Ran a compression test on the motor- All good there, 155-160psi


I've messed with the timing, tried retarding it, advancing it. Nothing helps, Advancing it makes it ping while it's *******, Retarding it makes it idle crappy


Things left open that COULD be a problem?
- TPS
- Ignition module (i doubt it, it's out of my 91 which runs strong)
- EGR valve and stuff
- Something to do with timing or the distributor???
- Computer, or PROM chip ??

And PLEASE don't say it's normal because it's a 5400lb truck. it's NOT normal what it's doing, i know the truck will be slow because it's a 305 ,but this is insane what it does. the RPM literally does not go up and it makes a ferocious roaring sound and just fall flat on it's face....and it has NO trouble codes, it just gives me code 12...the light is never on and never has been, only when i unhook the CTS or something is when the SES light comes on. otherwise, just code 12

I'm lost, i found a similar problem on here, and the problem was the guy's fuel pump, so i replaced it. still have the problem!! AHHH!!

Thanks
Brandon

crossy's son

Anything?

panhead201

www.thirdgen,orgHi,new parts is meaningless anymore,theres a lot of reman junk.They just clean it up and throw it in a new box.Put a fuel pressure guage on it.Sounds like a kinked line,low voltageclogged screen in tank.Or a sticky valve,burned valve seat,flat spot on cam,timing advance is dirty,rusty,whatever,I'd check fuel pressure first,vacuum modulator next,fuel pressure regulator.Autozone will rent you a fuel pressure guage,vacuum pump.put the fuel pressure guage right on the inlet to tbi.If all else fails,take a rubber hammer and beat on the tankThose lines in the pump kink really easy.

panhead201

What color is your spark?put a vacuum guage on it and look for a pressure drop.Vacuum leak could be anywhere.Airbox door under the glovebox door.

panhead201

Ithink theres a speed limiter built into chip.Gm high performance website tech help,maybe.panhead201