North American Turbocoupe Organization



That pesky stumble at different RPM
Wags88TC Offline
Senior Member
#1
I remember reading other guys posts about this(that's right, thought it'd never happen to me). At varying RPM while driving and sometimes sitting at a light-it just stumbles! The last few days it's even stumbled so far it died, sitting at idle! This morning it wouldn't start. I'm thinkin' it's a fuel problem(dropped the tank 'cause of a leak-it's the fuel fill grommet; and put in the Walbro pump, since I'm there)but not ready to rule out electronics!
Steve Wagner
Nato member
84 SVO
88TC, 5 speed, StageII Star clutch w/ StageIII pressure plate,lightened flywheel, K&N in fender, gillis valve, 255lph Walbro, Kirban adj.FPR,Bypass valve, 3" exhaust (high flow cat/ Magnaflow muffler), A-pillar gauges(A/F & Boost), 16" ARE 5 spoke wheels 7" front 8" rear(225/50VR16 / 245/50VR16 Yokos'). Subframe connectors
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Dan E Offline
Posting Freak
#2
Wags:

I am still fighting the same thing. I don't think our TC's like it if they can't do this !!!

I still contend that the EEC-IV has to do with some of it.

However, usually the things to check are (run the codes first):

TPS setting
O2 Sensor
IAC
Fuel Filter
FPR
VAM
TFI / PIP

Just a few things to go on...

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Dan Eaves
88TC 5spd, Crower 5.5" Sportsman Rods, Short Wiseco Pistons bored .030" Over, Ported Head with Polished Combustion Chambers, Gutted & Polished Upper, Ported & Polished Lower, Polished T/B, Ported E6, SVO T3 .63AR Turbo, 3" DP w/No Cat, 2 1/2" single cat back w/DynoMax Super Turbo Muffler, RR Cam, K&N in Fenderwell, Gillis Boost Valve, Centerforce I Clutch, Removed A/C, Polished Wheels, Polished Valve Cover, Polished Crank and W/P Pulleys, Walbro 255LPH HP Pump, Kirban Adj FPR, and the DAMN Heater Core is new too !
Dan Eaves
88TC 5spd Vermillion Red, Polished...everything...
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Jeff K Offline
Administrator
#3
When did you last do a complete tune up? These cars seem to be extremely sensitive to the brand and condition of the plugs, wires, cap, rotor, TFI and PIP generator. Try a fresh set of Motorcraft plug wires and Motorcraft AWSF32C or Autolite 762 plugs gapped at .030 to .032, and new Motorcraft cap and rotor. Run the codes and look for a continuous memory code 14: intermittant loss of PIP signal.... if you get that code, your miss is ignition related for sure, but even if you dont get that code, it could still be an ig. problem. Sometimes that code means a PIP or TFI heading south, but it can also be caused by bad plugs and wires. Also check teh batt to frame, batt to EEC and motor to frame grounds, as well as the orange wire 02 ground at the turbo inlet elbow. Wiggle the TFI connector and see if you can get the car to act up while wiggling it. These TFI connectors seem to have a habit of going bad.

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Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 20 psi, forced air intercooler, water injection, bypass valve, Ranger roller cam, subframes, etc., etc.. // 86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP nitrous, ignition, gears, suspension, etc., etc.... // 91 Escort: Bone stock winter car // 00 Windstar (wifes vehicle)
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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Noname
Guest
#4
My experience with this problem leads me to suggest a tune-up. I've noticed that a dirty cap/rotor that on other cars would not have caused problems on other cars, isn't acceptable on TC's. Also, the bypass valve should be cleaned regularly with brake cleaner. My advice is first look at all the simple, basic stuff. Most times it is not expensive electronics or sensors, but rather simple things like plugs, wires, etc. Hope this is of some value to you.
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Dan E Offline
Posting Freak
#5
That actually made me recall something...

The rotor and the inside distributor cap terminals (at least on mine) have a habit of getting a corrosion/oxidation build up on them. I just scrape that off and use dielectric grease on them (not the center/top terminals).

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Dan Eaves
88TC 5spd, Crower 5.5" Sportsman Rods, Short Wiseco Pistons bored .030" Over, Ported Head with Polished Combustion Chambers, Gutted & Polished Upper, Ported & Polished Lower, Polished T/B, Ported E6, SVO T3 .63AR Turbo, 3" DP w/No Cat, 2 1/2" single cat back w/DynoMax Super Turbo Muffler, RR Cam, K&N in Fenderwell, Gillis Boost Valve, Centerforce I Clutch, Removed A/C, Polished Wheels, Polished Valve Cover, Polished Crank and W/P Pulleys, Walbro 255LPH HP Pump, Kirban Adj FPR, and the DAMN Heater Core is new too !
Dan Eaves
88TC 5spd Vermillion Red, Polished...everything...
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Scott Evil Offline
Senior Member
#6
Does the motor really have bypass valve or is it a blow-off valve?

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"I thought about being a veterinarian, an evil veterinarian."

1988 TC Black/Red Leather
2001 Audi S4 Silver (the fastest color)
1986 SVO 1D <19,000 miles
2001 Audi S4 Silver (the fastest color)
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Dan E Offline
Posting Freak
#7
Quote:Originally posted by Scott Evil:
Does the motor really have bypass valve or is it a blow-off valve?

On a Stock one...it has neither. It has an IAC (Idle Air Control) sometimes called and IAB (Idle Air Bypass [valve]).

Just to be clear...a Blow Off Valve or Bypass Valve have to do with re-routing the air charge away from the turbo when the Throttle is closed quickly (like when shifting) and the air charge reverses.



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Dan Eaves
88TC 5spd, Crower 5.5" Sportsman Rods, Short Wiseco Pistons bored .030" Over, Ported Head with Polished Combustion Chambers, Gutted & Polished Upper, Ported & Polished Lower, Polished T/B, Ported E6, SVO T3 .63AR Turbo, 3" DP w/No Cat, 2 1/2" single cat back w/DynoMax Super Turbo Muffler, RR Cam, K&N in Fenderwell, Gillis Boost Valve, Centerforce I Clutch, Removed A/C, Polished Wheels, Polished Valve Cover, Polished Crank and W/P Pulleys, Walbro 255LPH HP Pump, Kirban Adj FPR, and the DAMN Heater Core is new too !
Dan Eaves
88TC 5spd Vermillion Red, Polished...everything...
Reply

Scott Evil Offline
Senior Member
#8
Quote:Originally posted by Dan E:
On a Stock one...it has neither. It has an IAC (Idle Air Control) sometimes called and IAB (Idle Air Bypass [valve]).

Just to be clear...a Blow Off Valve or Bypass Valve have to do with re-routing the air charge away from the turbo when the Throttle is closed quickly (like when shifting) and the air charge reverses.



That is what I was thinking. Just thought I would ask anyway.


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"I thought about being a veterinarian, an evil veterinarian."

1988 TC Black/Red Leather
2001 Audi S4 Silver (the fastest color)
1986 SVO 1D <19,000 miles
2001 Audi S4 Silver (the fastest color)
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