92 5.0 sputtering at WOT - Third Generation F-Body Message Boards

cfbird · 05-29-2009, 07:30 PM

I have been modding my L03, new cat back, new peformer tbi intake, MSD ignition, wires, distributor, new plugs, custom TBI mods, 55# flow matched injectors, injector spacer, adjustible FPR, inline fuel pump. I am running out of ideas on what is making is sputter at about 4000-4100 RPM and up? any help would be great.

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8t2 z-chev · 05-29-2009, 11:16 PM

could be a bad coil or ignition module.

cfbird · 05-29-2009, 11:22 PM

the msd coil and module are only about 3 months old

transam85dudeman · 05-30-2009, 04:06 AM

Its maybe your timing or gap on plugs. I had a coil that worked just fine, but after 5minutes of warming up, it would fail. so it wasnt working. My sister old truck did the same thing only at 1000rpms though. i tried a lot. but i always suspected it a timing advance issue. try adjusting your TPS also. that has to do with the computer's wot signal!

cfbird · 05-31-2009, 01:31 AM

timing is set 3.5 BTDC, plugs are gaped to factory. i've been searching a little and think im gonna replace the msd blaster coil with a msd HVC blaster coil seems like the standard blaster coil just cant stand in the higher rpms since its pretty much a stock replacement. i dont know much about adjusting the TPS how would i do that.

cfbird · 05-31-2009, 01:40 AM

what would be a good gap setting they are set at .035 now

transam85dudeman · 05-31-2009, 04:00 AM

0.035" is cool, thats stock, im guessing you need to diagnose your TPS. that tells your computer to go all out. (WOT). When your computer goes into WOT MODE< it ignores a majority of sensors. ha, maybe check your fuel charcoal canister to see if maybe there a vacuum leak. I know that a lot of hot rodder's run there TPI setup in limp mode, but as soon as they wot, they haul ***. TPS should be at .555volts.

cfbird · 05-31-2009, 01:32 PM

how do i check the TPS sensor for the .555 volts. this is my first TBI car and dont know very much about checking sensors. i have replace every vacume line on the car now if the charcol canister itself leaks i dont know, i will have to look into that today.

cfbird · 05-31-2009, 11:57 PM

i went too check the TPS voltage and noticed the black wire was worn about half way through so im gonna replace that and see what happens.

cfbird · 06-02-2009, 12:15 AM

well i replaced wires to TPS, TPS reads .498 closed and 4.73 WOT. i read that .45 to .55 was good, so the TPS seems good to me. so im going to replace the coil friday, i'm just about out of ideas.

cfbird · 06-05-2009, 07:57 PM

ok, new coil, new module, new TPS, new air charge temp sens. and its still the same.

akmusclecar · 06-06-2009, 01:08 AM

Do you know what your fuel pressure is? Sounds like it could be your pump going out or clogged. Is it the original pump? If you have a A/F gauge you can hook it up to see if the car is leaning out.

cfbird · 06-06-2009, 11:48 AM

I bumped the fuel pressure up to 15 PSI and that didn't help. i have an accel inline fuel pump along with the factory intank pump. I just downloaded some data logging software and orderd the cable witch will be here tues. or wed. then hopefully i will know a little more about what is going on with the car.

cfbird · 06-22-2009, 06:44 PM

Advancing inital timing to 6 DEG BTDC helped alot but i dont see what would cause it too need timing to help the problem just don't seem right.

transam85dudeman · 06-22-2009, 08:02 PM

hey i was thinking, did you happen to replace the fuel filter? and i dont think you need an inline pump, your tank pump is all your car needs. PLUS theres usually a filter screen on the tank pump that sometimes gets clogged. if you really want to, inspect the check valves on the vacuum lines and inspect the EGR diaphragm. i was reading up on TPS-its should be 0.525 volts. um and id clean the Idle air control valve. might wanna vacuum test the vacuum lines. the fuel pressure shouldnt be higher than 13psi, maybe try lowering it, and check the screens on the injectors for clogging. the hesitation could be lack of atomization due to clogged injectors screens.

cfbird · 06-23-2009, 11:56 PM

i put the inline fuel pump in place of the factory fuel filter and put a new fuel filter under the hood on the rubber feed line by the fenderwell, i installed the inline fuel pump because once i get it running right, i plan on getting a NOS system after a few more mods . i have a new EGR valve and i double checked it before i installed it just to be safe. i could only find one check valve and it seemed to be fine, looks old though, i've already replaced all the vacume lines. with the new TPS it reads .54 volts. i read up on cleaning the IAC just havent got around to it yet. i just installed new flow matched injectors from turbo city, the spray pattern looks pretty good to me, but i realy wouldn't know exactly what to look for. i'll go lower the fuel pressure once i get done with this message, with the adjustible FPR i cant get the pressure below 13.5 PSI. i dont want to pull the factory pump untill its the very last option so i dont have too cut a hole in my trunk because it seems to be a pain in the *** to drop the fuel tank. im stumped on this one.

cfbird · 06-24-2009, 12:20 AM

i just lowered the fuel pressure as far as it would go and it would only drop down to 14.5 PSI so i dot know if i need a diffrent spring because when i installed the AFPR i went and bought a stock FPR rebuild kit from the local parts store so i would have fresh gaskets and a new spring to go with the AFPR.