North American Turbocoupe Organization



stumble/hesitation on full boost
Tbird-fanatic Offline
Senior Member
#1
Well everything was fine before the head gasket blew. Everything went fine, the head had a full valve job before I reassembled it. Ignition timing is dead on at 10* with the spout out. As far as I can tell I have no boost leaks, but Im gonna look into it a little more tomorrow. Cam time is on using the string method(timing mark is broke off).

Idles almost perfect and runs great until it approaches 10 psi, then it starts to stumble/hesitate. Especially if Im only in the throttle hard enough to mantain speed going up a hill. If I go WOT its not as bad, but its still there. Im running out of ideas and need a little advice here. Mods and year are in my sig. Thanks in advance guys.
1988 Tbird TC - in pieces - barn find - mods beginning while restoring
2000 F250SD XLT CCSB 7.3 Powerstoke - Daily Driver - AFE intake, Swamps tunes, straight piped
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Pete D Offline
Administrator
#2
Any codes?
Done a pressure test of the intake system?
Pete Dunham


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Tbird-fanatic Offline
Senior Member
#3
Havent gotten a chance to check for codes. Not sure how to do a pressure test of the intake system. Is there a write up on how to some where.
1988 Tbird TC - in pieces - barn find - mods beginning while restoring
2000 F250SD XLT CCSB 7.3 Powerstoke - Daily Driver - AFE intake, Swamps tunes, straight piped
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Tbird-fanatic Offline
Senior Member
#4
Nevermind on the write up. Just found it and I may have some of the pieces here already to put one together.
1988 Tbird TC - in pieces - barn find - mods beginning while restoring
2000 F250SD XLT CCSB 7.3 Powerstoke - Daily Driver - AFE intake, Swamps tunes, straight piped
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Jeff K Offline
Administrator
#5
Possible dead spot on the TPS or VAM? Measure TPS voltage (green to black) with key on engine off to see if voltage smoothly goes from .9x V to 4.5 V or so as throttle is opened. Do the same with the VAF (BK/W to W/BK wires) while manually pushing flapper door open. Closed around .35 V, fully open around 4.5 V.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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Tbird-fanatic Offline
Senior Member
#6
Adjusted the TPS, put on new Motorcraft plug wires, those were a big impovement over what it was. It actually seemed a little quicker from a stop. Still had a slight issue so I decided to check the plug gap like had been suggested to me to. They had increased gap a bit, so I regapped them closer to what was suggested. Havent been able to take it for a spin yet. Every little thing so far has made a difference, I cant test it at the full 15 psi I was running right now til my replacement turbo to intercooler boot arrives. I blew the original one almost in half!!! LOL Guess it was a little weak after 24 years!!
1988 Tbird TC - in pieces - barn find - mods beginning while restoring
2000 F250SD XLT CCSB 7.3 Powerstoke - Daily Driver - AFE intake, Swamps tunes, straight piped
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Tbird-fanatic Offline
Senior Member
#7
Well I dont think its all over yet. I swear Im hearing an air leak as the turbo is spooling up that wasnt there before the head gasket blew. So something didnt go back together the way it was. So I am building the intake system pressure tester. Hopefully this will find my problem and Ill be back to good. Should be testing tomorrow.
1988 Tbird TC - in pieces - barn find - mods beginning while restoring
2000 F250SD XLT CCSB 7.3 Powerstoke - Daily Driver - AFE intake, Swamps tunes, straight piped
Reply

Tbird-fanatic Offline
Senior Member
#8
Found one air leak at the egr valve. The egr was actually crack by the top bolt. Im still here what sounds like a air leak prior to the turbo spooling, but Im having a hell of a time tracking it down.
1988 Tbird TC - in pieces - barn find - mods beginning while restoring
2000 F250SD XLT CCSB 7.3 Powerstoke - Daily Driver - AFE intake, Swamps tunes, straight piped
Reply

Not B Anymore Offline
Administrator
#9
When you pressurize the intake, spray soapy water around where there could possibly be leaks. Works much better than just listening for them.
Brian Leavitt
'86 TC 5-Speed -- MS2x w/COP | 83 lb. injectors | T3/T4 50 Trim Stage 3 .63AR | Full 3" Exhaust - No Cat | Motorsport FMIC | Ranger Roller | Ported E6 | Walbro 255HP | Kirban | 20psi | 120-amp 3G | 8.8" 3.55 rear | '03 Cobra Wheels
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Tbird-fanatic Offline
Senior Member
#10
Well we would listen to get a general area and then start spraying anything that could leak in the area. Around the turbo seems to be the hardest with the intercooler there. Im still running the temp turbo to intercooler boot i came up with. Still waiting for my permanent replacement to show up.
1988 Tbird TC - in pieces - barn find - mods beginning while restoring
2000 F250SD XLT CCSB 7.3 Powerstoke - Daily Driver - AFE intake, Swamps tunes, straight piped
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