North American Turbocoupe Organization



Cold Rough/Rich idle /Bucking under load
Silver85TC Offline
Member
#1
Ok, I'm really starting to get frustrated. My 85 was running really great up until I decided to change the spark plugs last month. Short story long......

Installed new autlite 764's gapped at .034. The car ran good for a few days then started to idle really rough just after start when the engine was cold...almost like it was misfiring...exhaust smells really rich as well. Idle improves under part throttle and when engine warms up. The car also started to buck under load when boosted....never did that before. Around the same time, I noticed the fuel pump starting to get reaaaallllly noisy. Thought I was having a fuel problem. Changed fuel pump/filter...idle/boost problems still there.
Next, plug wires/cap/rotor were a couple years old, so I installed new ford wires and a Napa cap and rotor. Idle/bucking problems persisted.
Well, plugs are cheap, maybe I had a bad plug....once again, installed new autolite 764's gapped at .034. Arrrrgh ! No change. Problems still there!
Checked FPR vacuum hose....seems fine....no gas smell. Checked various electrical connectors. All seemed fine. Played with IAC valve connector...now car wouldn't start. Doh!!! Removed/cleaned IAC valve and car started again, original idle/bucking problems remained.
I should mention that no codes have shown up throughout this ordeal....always 11.

So, after all that, I'm running out of ideas. I'm thinking possible IAC valve or VAM. Would either of those cause both my rough/rich idle and bucking problems? The other thing that it could possibly be is the TFI I guess, but no codes are showing up.

ECT sensor is only a couple of months old, so I don't think it's that.

Do you guys think I'm on the right track?

Heeeelllllpppp!
85 Turbo Coupe - 5 spd, factory alarm, automatic temperature control....STOCK!! and in nice shape!

95 Black Mustang GT - 5 spd /w black leather
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88turbo Offline
Member
#2
i changed from the 764s in my '86 to ac delcos gapped at .038 and my car runs tons better now
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Silver85TC Offline
Member
#3
Anything I've read on this bb says you should use autolite 764's gapped between .031 and .035. Anyone else?


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85 Turbo Coupe - 5 spd, factory alarm, automatic temperature control....STOCK!! and in nice shape!

86 Mustang GT - 5 spd, T/tops

95 Black Mustang GT /w black leather
85 Turbo Coupe - 5 spd, factory alarm, automatic temperature control....STOCK!! and in nice shape!

95 Black Mustang GT - 5 spd /w black leather
Reply

Silver85TC Offline
Member
#4
A couple more things. When I pulled the plugs the second time, all four were black...definitely running rich.

So, what could be causing rich condition/crappy idle/bucking under boost?

IAC - could cause crappy cold idle problem, but I don't think it does anything while driving? Correct me if I'm wrong.

O2 sensor is a couple of years old. Could cause rich condition/bucking problem under load. I don't think its used at cold idle though. Again, correct me if I'm wrong.

TFI - original as far as I know. From what I've read, this generally gives problems when the engine is hot, not cold, and the engine generally won't run at all with a bad TFI.

ECT - could cause rich idle/bucking problems, but I just replaced this sensor 2 months ago with a new one.

TPS - havn't checked this yet. Could it cause both idle and bucking problems?

VAM - I think this could definately cause my rich/crappy cold idle and bucking under load problems if it was sticking/worn etc.

So after thinking about it some more, I'm leaning towards the VAM or possibly the TPS. Do you guys think I'm on the right track?

Any opinions appreciated
Thanks


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85 Turbo Coupe - 5 spd, factory alarm, automatic temperature control....STOCK!! and in nice shape!

86 Mustang GT - 5 spd, T/tops

95 Black Mustang GT /w black leather
85 Turbo Coupe - 5 spd, factory alarm, automatic temperature control....STOCK!! and in nice shape!

95 Black Mustang GT - 5 spd /w black leather
Reply

Kev Offline
Posting Freak
#5
Since your car was running good before you decided to change the spark plugs, I would look at stuff that you had to disconnect to get to the spark plugs first. Like putting the right spark plug wire back on the right spark plug. Did you hook the TPS connector back up if you unhooked it? Do you have any sort of intercooler hooked up? The air flow between the turbo and throttle body is soooo important and would cause the exact conditions that you are describing if one clamp is loose or there is air escaping anywhere. You also mentioned that the car wouldn't start until after you messed with the IAC connector so I'd make sure that the connector was good.
Kev
1988 TC 5spd
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Silver85TC Offline
Member
#6
Hi Kev,

I've triple checked the plug wires and everything is on correctly. I don't have an intercooler, so there was nothing to remove to get access to the plugs. I havn't touched the wiring for the TPS. I had the no start last night after I played with the IAC connector. Played with the IAC connector some more, cleaned IAC and got car started again, but original problems persist.

I'll double check the turbo/throttle body hose clamps tonight when I get home, but I havn't touched them, so I don't think that would be it.
85 Turbo Coupe - 5 spd, factory alarm, automatic temperature control....STOCK!! and in nice shape!

95 Black Mustang GT - 5 spd /w black leather
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Jeff K Offline
Administrator
#7
Have you checked your fuel pressure?

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Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 21 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 // 02 Taurus Vulcan(wifes car)
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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Pete D Offline
Administrator
#8
I emailed you some info for testing the fuel system and the ECT. In a sperate e-mail I'm sending you some tests for the TFI/PIP. Only need an ohm meter

What brand of ECT did you use. Personally I prefer the Ford part for this sensor.

My guess is the problem is not related to your original installation of new plugs. i think it was just coincidence.

Since you know it rich, run the fuel system diagnostics first.
Pete Dunham


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Silver85TC Offline
Member
#9
Hi guys

I don't have a fp guage so i havn't been able to check the actual fuel pressure. The new fuel pump that I installed was a Holley 155 lph.

I bought the ECT from Napa. I'll run the diagnostics when I get home.

One more question. Could the PIP be causing the problems, yet not throwing a code?

Thanks
85 Turbo Coupe - 5 spd, factory alarm, automatic temperature control....STOCK!! and in nice shape!

95 Black Mustang GT - 5 spd /w black leather
Reply

Pete D Offline
Administrator
#10
I sent you info for testing the TFI and PIP.

It is probably more likely that a code 14 - PIP signal loss could be caused by bad plug wires or spark plug problems than no code being set.
Pete Dunham


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