stumble/hesitation on full boost

Well a little more info. Ive started to hear a howl before I hear the normal turbo spooling sounds. Also Ive been having some extended cranking hot and cold.

Well Im still trying to figure this out. Ive been thru about everything I can think of on the intake side for leaks and if its leaking anywhere itll be so small it shouldnt matter Ive been doing some searching and other than boost leaks Ive found fuel pressure issues or possibly the O2 sensor. One thread I found that the guy had a head gasket blow, it was suggested to try a new O2 sensor. Which makes sense since I was dumping massive amounts of white smoke out the exhaust. I do have an extra one from my extra motor, so I may pull it off and try it and if thats it Ill buy a new one. Im also gonna stop down at my buddys shop and see if I can borrow his fp tester. If anyone else has any suggestions let me hear them. I starting to get really frustrated.


Also its still running fine with no boost and then after about 5 psi it just falls on its face and rpms dont matter. If I run it up to 4000 without boost its will do it just like it does running 2500. Going up hill I have to downshift to 4th just to keep speed and out of boost. I need to figure this out really soon, a turbo charged 5.0 starts to get more tempting the more I fix little issue with no improvement!!

Also a little more info I forgot about. When I was first constantly rechecking cam timing, I forgot to set ignition timing and took it for a spin with the timing REALLY advanced and it ran a little weird but it pulled all the way thru boost. Dont know if that would happen now, but thought it was worth bringing up.

Put a scanner on and all I got was the system pass code. I did put a fuel pressure tester on and with and with out vacuum was perfect. Pressure also rose with boost just the way is supposed to up to 50psi at WOT at about 10psi of boost. Double checked cam timing and it was DEAD on. Swapped out the O2 sensor with the one from my other motor and in the process I noticed a possible boost/vacuum leak. When I installed the Gillis I didnt have a plug to block off the one set of nipples that your supposed to. So I looped a hose. Looked today and there was a tear in it. Fixed that, but I wont be able to go for a spin till tomorrow morning. So my fingers are crossed!!!

Well im still having issues, just been trying to pick away at little things hoping one of them was the problem. I have my Gillis set at about 13 to 15 psi running only premium fuel. It still feels like its falling on its face at about 8 psi, but I discovered upon accident the other morning that after 4500 rpms it takes off like a raped ape all the way up to red line. Which to me seems weird since I thought the RR was useless up that high. So I finally found the correct procedure on here for the KOER test. I got a few Im only gonna post the ones that I cant explain

41- system indicates lean
73- Insufficient Throttle Position Change During Dynamic Response Test (which I ran all the way to the required rpms about 3500)
76- Insufficient Vane Air Flow Sensor Output Change During Dynamic Response Test

Any help here would be greatly appreciated.

Well ran the code agian right after getting home and those 3 didnt come back up. But went to my cell phone store to get my wifes phone taken care of and the car wouldnt start. After some running around in this heat diagnosing, i discovered little to no fuel getting to the motor. So either the pump went out or the hose ruptured agian. If its the pump that could explain this running problem. Enough pressure but no enough volume.

I'm sure you are, but if you are not aware of the procedures for testing the fuel pump and system...

http://www.turbotbird.com/techinfo/Fuel_...ostics.htm

http://www.turbotbird.com/techinfo/Fuel_...ostics.htm

Been thru most of that, did the jumper wire to run the pump and i cant hear it running and im getting little to no fuel at the test port. Ill find out tomorrow though, taken to the shop i work at and doing a full diagnosis to it. Something just tells me though that the 24 year old pump has about had it.

Well the original pump finally bit the big one!!!! The bulk of this issue has cleared up, so far (knock on wood). My buddy had an extra Walbro 255hp laying around, so he hooked me up with it. Im gonna go thru tomorrow and check some of the adjustable things like base idle(tps to since it will be affected) since its idleing a little low. Otherwise she sounds great, no popping out of the exhaust at idle anymore, even seems to idle smoother.

Sounds like good news. Congrats.

Well that wasn't the full problem, but I did discover what was. I was still having issues under full boost, so I kept tinkering. Low and behold,I though well maybe something is tripping the knock sensor. So I unplugged it and went for a ride. No issues and no detonation, so either the sensor took a dump on me or the sensor is mistaking something else for detonation. So now I need to figure out what is causing it.