North American Turbocoupe Organization



At My Wits End!!! kinda long
turbocoupes Offline
Senior Member
#1
For about 9 months have been chasing a misfire/bucking in my 87 5spd TC. Did an exstensive search in all catagories here and at TF. The problem is a mild to severe missfire/buck during light to easy "tip-in"/acceleration ALMOST everytime...under moderate to hard acceleration with boost...runs great. To date have swapped throttle body for TPS,MAJOR FoMoCo tune up with PCV,IRCM with BPM,ckd fuel pressure...all good FPR not leaking ,swapped ignition switchs,4 dizzys (now NAPA reman is in),swapped 2 known good ECMs,replaced harness from dizzy to firewall(wasnt replacing whole harness yet)replaced timing belt and tensioner...TIMING IS CORRECT. Codes were KOEO 54 air charge(replaced and most other codes went away)...CMC was 14 erratic PIP and KOER 21 coolant sensor(repl for GP),24 intake air temp sensor,72 TPS(Throttle body replaced and basic idle and TPS have been set per FORD manual),75 Minimal air flow at VAM.Have gone over all of the above and replcd vam hoses and yes the intercooler hoses are on right with no leaks...have gotten rid of all codes EXCEPT CMC 14 Erratic PIP...hence I still have a miss/buck...short of rplacing the engine to ECM harness...any ideas???
Garry McVey "BIRDS OF A FEATHER" TBird TC owners are usually wingin' it
TC's 83 project, 86 donor for 83, 86 FUN street car daily driver with speed equipment from Red 88 donor, 87 blue to be stock street car, 87 red donor for blue and others, 87 red donor, 88 street and strip(now a donor) 14.01 chasin 13.0's, 87 XR4ti project,
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Walsted Offline
Posting Freak
#2
Possible bad injector?
Mike Walsted - Sold my 1986 5-speed TurboCoupe
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Jeff K Offline
Administrator
#3
The CM 14 can come from electrical noise interfering with the low voltage PIP signal to the PCM. Can be caused by EMI/RFI from wires, bad cap/rotor, etc, but it looks like you have that covered.

Bad grounds can also lead to electrical noise causing interference with the PIP signal. Many years ago, I kept getting a CM 14, but never really noticed much bucking, etc. The engine to frame ground was iffy, so I cleaned that up, and added a second engine - frame ground and the problem never returned. Check batt ground at motor, and batt terminal connections.

What shape is the alt in? Any chance it has a bad diode (open) which will lead to electrical noise? Got a scope to look at system voltage to see if it is noisy?

Is the TFI harness shield intact and grounded properly at the PCM?

As Mike said, could possibly be a partly plugged injector or leaky injector. Got a known good spare set to throw on?
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.
11 Crown Vic Interceptor
14 Toyota Camry (wifes car)
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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Matt S Offline
Posting Freak
#4
My car ran funky with 2 different Napa PIP's; occasionally I'd get a cm14 regardless of TFI brand. I bought a Motorcraft PIP and TFI together and that smoothed out alot of things.

However I still have a slight miss/buck at light throttle, 25-35mph that is most pronounced when cold. I think my last hurdle is electrical noise. I'm going to fork over the change to Magnecor 10mm wires. Pricey, but I like what I read about them.
Sold it Sad*
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turbocoupes Offline
Senior Member
#5
I would have thought that an injector concern would magnify under boost??? uh maybe not with additional fuel and pulsewidth??? Do have known good ones to try if need be. The "electrical noise" I didn't think about...(just found out after all these years the TFI was shielded!!!)and the shield IS flaking apart...other than replacing the complete engine harness is there a way to repair the shielding on the TFI wires??? I did add another gound from battery to engine but not engine to body I'll do that first...the altenator "seems" to be in good working order...yeah I have a scope will ck that also...I could just take the belt off and see if the car runs ok without the alt. right? shouldn't be any noise then? I pretty much ruled out dizzys and TFI/PIP by trying 3 known good dizzys. Thanks for all the input guys...
Garry McVey "BIRDS OF A FEATHER" TBird TC owners are usually wingin' it
TC's 83 project, 86 donor for 83, 86 FUN street car daily driver with speed equipment from Red 88 donor, 87 blue to be stock street car, 87 red donor for blue and others, 87 red donor, 88 street and strip(now a donor) 14.01 chasin 13.0's, 87 XR4ti project,
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Walsted Offline
Posting Freak
#6
Quote:Originally posted by turbocoupes:
I would have thought that an injector concern would magnify under boost??? uh maybe not with additional fuel and pulsewidth???
If the injector letting more fuel through than it should, the problems would be worse at low engine loads than high engine loads.

The main reason I suggested injector was that was a cause of one of my gremlins. I had replaced the usual suspects to no avail. I finally measured resistance across each injector, and found out I had a bad one. Luckily, RDOG had a few spares just down the road a few (dozen) miles.

Hope this helps
Mike Walsted - Sold my 1986 5-speed TurboCoupe
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turbocoupes Offline
Senior Member
#7
Makes sense!
Garry McVey "BIRDS OF A FEATHER" TBird TC owners are usually wingin' it
TC's 83 project, 86 donor for 83, 86 FUN street car daily driver with speed equipment from Red 88 donor, 87 blue to be stock street car, 87 red donor for blue and others, 87 red donor, 88 street and strip(now a donor) 14.01 chasin 13.0's, 87 XR4ti project,
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Jeff K Offline
Administrator
#8
Sure, you could run the car with the alt disconnected and see what happens, as long as the batt voltage doesnt drop too low while testing it, as low system voltage can in itself cause problems.

Shielding: If the original is bad, you could always fab something up, like wrap wire mesh screening around the harness or something. Note that it is important that the shielding be grounded at only one end, otherwise ground loops currents can flow and make things worse.
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.
11 Crown Vic Interceptor
14 Toyota Camry (wifes car)
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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Mike C Offline
Senior Member
#9
I must be the the only vote for air or vacuum leak. This is the one I chased for months, spent every weekend changing the next part I read about during the week. By Tuesday I had the same problem, Maybe the engine twisting or the hood shaking was causing it to come off? It was an intercooler hose that was split internally, never found it, saw it after I changed it, just because it was the last thing left!!
Another .10
Mike C
86 5 speed TC black with MS spats and spoiler since 88, 3.73 8.8 since 89. Fresh rebuild at 240K with new Racer Walsh roller cam, 88 hood. All 3" exhaust w/3" performance cat. 13" Cobra brakes,SFC, Max/Motorsport C/C plates,adjustable lower control arms w/ double adjustable uppers. Konis & Eibachs.
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turbocoupes Offline
Senior Member
#10
OK! After HOURS of retesting/rechecking EVERYTHING...squirting everything imagineable all over the engine and lines/hoses/etc,ohm'd injectors and harness...unpluged alt. harness...wrapping TFI/PIP harness...added HEAVY ground from engine to frame/unibody...NOTHING changed the miss/buck. SOOOOO I figured I would restart at the basics ...OHMAN!!! my long phillips is in the van and its in Baltimore! Oh well let me atleast try another COIL WIRE...Fired it up...no miss/stumble...give it a little throttle...still no miss/stumble...run to the store and back...NO MISS/BUCK/STUMBLE!!!YEEEHAAA!!! Looks to be Secondary ignition problem...Will get another set of wires TOMORROW!!! Looks like this engine WILL be going in the drag car after all in good shape!!!Who would have thought!!! Age old saying I should have remember..."just because it's new doesn't mean it's good"...THANKS for all the input guys!!!
Garry McVey "BIRDS OF A FEATHER" TBird TC owners are usually wingin' it
TC's 83 project, 86 donor for 83, 86 FUN street car daily driver with speed equipment from Red 88 donor, 87 blue to be stock street car, 87 red donor for blue and others, 87 red donor, 88 street and strip(now a donor) 14.01 chasin 13.0's, 87 XR4ti project,
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