North American Turbocoupe Organization

driving without TPS
longbedGTs Offline
Senior Member
As many do, I also had a problem with a crazy idle. Up to 1500, back to 1000, back up to 1700, ect...
I have unplugged the TPS until I can afford a multimeter and of course another TPS. Ive been driving like this for the past couple weeks and the only adverse effect I can tell is sometimes(1 out of 10 times) the idle will drop low and stall. My mileage is still at 23MPG, power is there, nothing has changed from when it was plugged in. Im tempted to just leave it and get a TPS whenever since its behaving so well, but I want to make sure Im not slowly damaging my motor by doing this. Any input? Thanks!
88 TC 5spd~money pit
88 TC 5spd~78K miles

Jeff K Offline
Not sure on this, but my guess is that no TPS input will be interpreted by the PCM as a major problem (TPS is a major input to the PCM) and the PCM will go into FMEM mode (limp home mode). Check ignition timing with SPOUT in. If timing is 10 deg over base (20 deg is base is set to 10 deg) and doesnt change with RPM or load, then PCM is in FMEM mode. The engine will run, but no where near at its full potential if it is in FMEM mode.
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

DonH Offline
Posting Freak
I'm not sure about the limp in mode, the EEC may have an alternative strategy for dealing with the lack of TPS, but leaving it disconnected is not going to damage anything.
1987 TC stock except ATR 2.5"
1983 Pontiac Transam T-top 5.7 T56 [email protected] top speed: 176mph
1978 Fairmont 2.3 4-spd Big-top S/W
1946 Willys CJ2A 134.2ci L4 No-top

sbhjr44 Offline
Senior Member
Try just disconnecting the IAC instead. My 87 had the same problem so just fooling around I did that and then adjusted the idle with the screw and it idled perfect although it would drop a couple hundred rpms when cold. I cleaned the IAC and the idle was great after that when I connected the IAC back up.
Stinger dual3"exhaust from dp & cat to magnaflows w/2.5 outlets w/tailpipes.Homemade CAI w/boost at18psi.MM c/c plates and tubular lca/front coilovers with Koni red adjustables all around. Ported/BV head/A237 and bobslog w/a stinger fmic set-up waiting to go on.86 stang gt w/motor and T-5 from a 86 TC w/3"SS dualexhaust w/cc plates and lowered 1.5".With volvo ic installed.

Keith Nubel Offline
Posting Freak
Just about everything the computer does is based on TPS, O2, and temperature. I don't see how the computer can possible work correctly with it.
1985 TC

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