North American Turbocoupe Organization



Funny idle after T5 swap
86thunderchicken Offline
Member
#1
I’m just trying to see what would make my 86 TC idle funny after I’ve swapped it to an 87 T5. I’m trying to rack my brain to figure out why. Only thing I could think of is vacuum but I only capped one vacuum line from the old C3 transmission. Any ideas as to why gentlemen? 

It will idle high for a little while then kinda bounce around
1986 TC 240,000 miles. Walbro 255. Soon to be under the knife for an 87 5 speed swap

1992 Mustang LX 5.0, headers, H pipe, and soon to have subframe connectors to boot!
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Jeff K Offline
Administrator
#2
What exactly do you mean by "idles funny"? Low idle, high idle, hunting idle?

You might be on the right track with the vac leak idea. Could have easily snapped or cracked one of the very brittle by now Nylon vac lines during the swap. Carefully check EVERY vac line in the engine compartment.
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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86thunderchicken Offline
Member
#3
It will start up and idle around 1500 for a few minutes then settle down to around 1000 rpms and after it settles down it will start dropping and try to keep itself running so it’ll drop to say 600 then rev back up to 1000 or so. It just keeps doing that over and over and keeps running just really oddly that way.
1986 TC 240,000 miles. Walbro 255. Soon to be under the knife for an 87 5 speed swap

1992 Mustang LX 5.0, headers, H pipe, and soon to have subframe connectors to boot!
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gtbird Offline
Member
#4
(11-22-2020, 06:19 PM)86thunderchicken Wrote: It will start up and idle around 1500 for a few minutes then settle down to around 1000 rpms and after it settles down it will start dropping and try to keep itself running so it’ll drop to say 600 then rev back up to 1000 or so. It just keeps doing that over and over and keeps running just really oddly that way.

Vacuum leaks definitely can attribute to those conditions. I used to find the caps on the unused ports of the vacuum tree dried out and cracked. New caps, and surging idle would be gone. Good luck.
1988 T/C Silver with red interior, fully loaded except for leather. 5 lug conversion with 97 Cobra wheels, Cobra 13" brakes up front, Mustang brakes out back, Koni adjustable shocks and struts, NOS Koni lowering springs . Maximum Motorsports control arms and caster/camber plates, subframe connectors.
SOLD September 2020. Will miss this car after 19 years of building/driving/showing....time for a new chapter in my life.
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Jeff K Offline
Administrator
#5
^^^ Ageed. BTDT more than once.

If you find a split / damaged / cracked spot in a Nylon vac line, and the rest of the line is still in good shape, just cut out the bad section and splice it back together with a small piece of 1/16" ID rubber vac hose. Done this many times on our older cars with great success and had this type of repair last for 20+ years.
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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86thunderchicken Offline
Member
#6
Any other ideas besides vacuum leak? I literally only changed the transmission from C3 to T5 and it had one vacuum line that went to the C3 and that was it. I capped it
1986 TC 240,000 miles. Walbro 255. Soon to be under the knife for an 87 5 speed swap

1992 Mustang LX 5.0, headers, H pipe, and soon to have subframe connectors to boot!
Reply





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