Fuel pressure is good, 39 psi at idle, 41 psi with key on engine off, 47 psi with simulated full throttle (vac line off). Pressure drops very very slowly after engine is off

Fuel Pressure reg has been replaced, walbro fuel pump, egr removed, ccp removed, injectors are not leaky, compression is good (174-182 after 5 strokes per cylinder), has knock retard when quickly punching the throttle with stock and madz28 tune. Engine has never ran good since the engine swap.

What else should i be looking for? I've been trying to figure this out for 3 months and have not fixed it, if i don't figure it out soon I will be taking it to a mechanic.

 

I had the same problem as well but it was my fuel pressure was WAY too high (more like 65 psi). Even yours is tiny bit high, it should be more like 43.5psi with the vaccum line off. You can try adjusting that down a bit if you have an AFPR, but more than likely that isn't what is wrong.

Another thing, do you have a descreened or ported MAF?

 

regular MAF, regular FPR

 

Try unplugging the MAF or swapping in a spare one. It's also possible that you have a bad MAF so unplugging it will make the car go to speed density. It's a shot in the dark, but well worth a try.

 

If i unplug the MAF, the LT1 will run at idle. If i give it any throttle with the maf unplugged the engine dies.

 

Thats really wierd. Are you unplugging it with the car running? I unplugged mine when I was trying to figure out why my BLMs were at 108 too and it ran just fine without it, even WOT. With it idling without the MAF, what are your BLMs? Are they the same?

 

" 41 psi with key on engine off, 47 psi with simulated full throttle "

That seems weird to me, it should be the same PSI with the car off, pump primed as with the vacume line off when the car is running...

 

i unplug the maf and then start the engine. I'll work on getting data for blms with maf unplugged, i'm having computer problems.

 

Could be bad O2 sensors also, although if both banks are 108 I wouldn't suspect that first.

 

my bad, i was reading it only with the engine off. While priming the pump the psi is the same, 47 psi.

I've changed out the O2 sensors b/c one wasn't reading correctly. Didn't change anything though.

 

You might look for exhaust leaks also. If you are leaking, fresh air can be sucked in fooling the O2's into thinking it is lean and then it will dump fuel making it very rich. My car was doing the samething and it is O2 related. It will run fine in open loop, then the moment it would go into closed loop, it would dump fuel.

 

No leaks. Runs bad in open and closed loop.

Finally got a laptop to borrow but can't get datamaster to work on it. I got 108blms in cell 18 while driving around slowly.

 

well i ended up having a bad map sensor and when i replaced that it got rid of the pinging/detonation.

Last nite i reset the battery and changed the oil and the blms at idle at cell 16 were 112/115 after letting it idle for a while, it may still drop to 108. This morning i decided to try it with the MAF unplugged and BLMS at idle were 135/138. I'm going to try swapping MAFs from another car but the other car has a de-screened MAF so i dont know if i can completely trust it.

Anyone have an explanation why the BLMs would go the other way with the MAF unplugged? I'm suspecting something with the MAF sensor but maybe its something else.

I barely tested it with the MAF unplugged but i revved on it once and it had a few degrees of spark retard.