North American Turbocoupe Organization



Misfire after ~3500 rpm, persists for about 60 sec
bigbillhell's Offline
Junior Member
#1
Hi all!

Want to start off by saying that I'm new here, thanks for letting me join!

Alright, I have an 88 TC, with no mods. When moving, as soon as I hit 3500-4000 RPM whether or not I'm at WOT, it feels like I have a misfire. I don't know if it would be valve springs as it persists for about 60 seconds thereafter. It will misfire whether I'm idling, or still moving, and again, no matter what I'm doing the misfire will go away after 60 seconds. Another issue is that as I'm pulling into a stop, I put the clutch in and take it out of gear. The RPMs will drop near stall for about a half second then recover to normal idle speed.

Here's what I've checked so far:
VAM is good
TPS is set correctly, doesn't jump in it's sweep
IAC is good
EGR disconnected (still occurs when connected, doesn't matter)
Fresh plugs, wires, plugs gapped to 32 as per sticker in engine bay.
TFI has been replaced with a known good TFI, didn't help.
The chingadera inside the distributor has been replaced, didn't help.
Timing set at 10 degrees BTDC with sp-out disconnected
No vacuum/boost leaks that I'm aware of.
Compression is 140 all cylinders
Stock FPR replaced with new stock part and adjustable FPR, both no change.
Fuel Pressure stable and at correct level, rises/drops with boost
Fuel is new, 91 octane
Fuel filter hasn't been touched by me, but assured by previous owner that it is new (less than 5k miles on it)
Assuming fuel pump is good because I don't have drops in fuel pressure under load

Starts and idles real nice, no misfires there, drives like a dream around town, but as soon as I'm at 3500 rpm it starts misfiring. Oddly enough, it does not misfire if I'm sitting in neutral revving to 3500, it only misfires if I go to 5000 in neutral.
2 things my father suggested I test :
Set the timing to 15, go WOT: experienced major pinging but NO misfire - NONE.
Disconnect vacuum to FPR, WOT again: Lean as all hell but NO misfire - NONE.

I am stumped. Engine runs perfectly normal, temp gauge needle is right in the middle when running about town. What do I check next?
Please help!

PS: FORGOT TO ADD - WHEN IT MISFIRES IT ALSO BACKFIRES WHEN THROTTLE IS "GOOSED"
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V6TBird87 Offline
Posting Freak
#2
Have you checked your cam timing? I've had similar issues with other cars due to cam timing.
1987 Thunderbird
1988 Turbo Coupe, 5-speed

aka Tbird232ci
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BogusSVO Offline
Member
#3
What TFI do you have?

If its not a motorcraft, it could still be the issue

The parts store brands, wells and bwd, along with the really cheap ones dont seem to ever work as well
Owns more Turbo FORDS than the law should allow....and still getting more

85 TC going under the knife
84 Turbo ranger --($800.00 ebay) Redneck work truck
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Turbo Cruiser Offline
Junior Member
#4
Sounds like injectors to me. Pull the vacuum line of your regulator, if fuel comes out while the engine is running, then it is shot.
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Jeff K Offline
Administrator
#5
^^^^ Even if the FPR vacuum line has a somewhat strong fuel smell to it the FPR is shot.

My first thought was valve springs, but that doesnt make sense since the engine free revs fine. Have you pulled the plugs to read them?
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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anasazi4st Offline
Senior Member
#6
bigbillhell's Wrote:The chingadera inside the distributor has been replaced, didn't help.

What *I* want to know is, is the "chingadera" a Motorcraft part, or can I get one anywhere? Sounds cool, I think I need one, I just have a regular rotor in mine. :giggle: :confused: :rotfl:

Seriously though...I'd agree, sounds like a fuel issue. Why not "tee" in a fuel pressure gauge and see what pressure you're getting at 5000 rpms at idle, up down or the same?

Have you pulled any EEC-IV codes?
Another proud dues-paying member.

1987 Turbo Coupe w/T5OD, 8.8 axle, grey smoke; most options. Got it in 1991 with 41K miles: 3 turbos, 2 heater cores, 1 T5OD full rebuild, 5 clutches, 1 head gasket, 2 Teves II ABS units, etc. later....
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