Engine Idle Problem

I have a 1987 Turbo Coupe pretty much stock with the exception of a K&N air filter and no catalytic converters. It’s an automatic and has approx 164000 miles. At a cold start up
The car idles fine for 2-4 minutes then the rpm’s start revving up and down continuously from 1500rpm down to just about stalling but as soon as it hits that point it kicks back up. The rpm’s bounce for 2-3 minutes then it goes back to normal. Now if you were to drive away or rev it to the 2500 rpm the engine would hesitate/sputter. It does this until it’s warm an then drives great then those same things happen again when it’s hot (driving it for about 45mins to a hour). It does this everyday.

These items have been replaced: tfi module (3 times), tfi pig tail, the computer, tps sensor, o2 sensor, coil, pick up in the distributor, fuel pump a year ago, egr 6mos ago, plugs, wires, cap and rotor pcv valve, fuel filter, fuel pressure regulator about a year ago. The things that have been checked: no vacuum leaks, no bad grounds, iac is good, I think all the wires and harnesses have been gone through and are okay, fuel pressure is good, charging system is good. The diagnostic test shows everything is okay. Please help this is driving me crazy. Thanks.

Quick question did you use motocraft TFI, wires, plugs? What about timing?

Do a search for idle problems and you should find a solution. What about the ACT sensor.

and you get no codes in all tests?

[This message has been edited by Icefire (edited 10-24-2001).]

Did you replace the PIP - stator assy inside the distributor when you did the TFI(s)?
You say the diagnostics were done, how about the KOER part. I'm thinking VAT or 02 but I would want to see codes for these items before I replace parts.

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88 TC X 2, 86 SVO, Main TC with K&N, 3"DP to 2.5"duals through Dynamax, Ric valve at 17+ and disconnected KS.
Elite Bodega 16" chrome wheels. Autometer pod w/ A/F and Vac/boost gauges.140 mph Motorsports Speedo New engine: Total Seal rings and TRW pistons, ported and polished head w/ cc'd chambers,1.59"exhausts, SS valves, gutted upper, knife edged lower, A-230 cam, Race Engineering Adj Cam Sprocket, Crowlers, ARP head studs, and rod bolts. Walbro 255 HP pump and Kirban adj FPR, T-3. Centerforce II, KB subs and jack rails.

Originally posted by Icefire:
Quick question did you use motocraft TFI, wires, plugs? What about timing?

Do a search for idle problems and you should find a solution. What about the ACT sensor.

and you get no codes in all tests?

[This message has been edited by Icefire (edited 10-24-2001).]

Wires, plugs, cap and rotor, pcv are motorcraft just not the tfi and the timing is at 10 deg. I will probably change the ACT sensor. What does the Act sensor do? Thanks

[This message has been edited by 87turbobird (edited 10-26-2001).]

Originally posted by Pete D:
Did you replace the PIP - stator assy inside the distributor when you did the TFI(s)?
You say the diagnostics were done, how about the KOER part. I'm thinking VAT or 02 but I would want to see codes for these items before I replace parts.

KOER part was done and there were no codes. O2 is new. The PIP has been replaced. What is VAT and where is it? Thanks

If you don't know what the ACT is and where it is, why change it? Send the money to me instead. [Image: biggrin.gif] The ACT is the air charge temperature sensor and it is located on the back side of the lower intake pointing at the firewall. It is the bottom of the two sensors back there. The other is the knock sensor. The VAT is the vane air temperature sensor and is located inside the vane air meter (VAM) which is the big metal block that has a hose on the back of it going to the turbo compressor inlet. VAT seldom fail, most problems are in the wiring or connector. Symptoms are hesitation, stalling and poor fuel economy. Try cleaning the connector to the VAM. I'd also clean the connector and check the wiring to the ECT (engine coolant temperature sensor) which is located between # 2 & 3 injectors on the lower intake.


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88 TC X 2, 86 SVO, Main TC with K&N, 3"DP to 2.5"duals through Dynamax, Ric valve at 17+ and disconnected KS.
Elite Bodega 16" chrome wheels. Autometer pod w/ A/F and Vac/boost gauges.140 mph Motorsports Speedo New engine: Total Seal rings and TRW pistons, ported and polished head w/ cc'd chambers,1.59"exhausts, SS valves, gutted upper, knife edged lower, A-230 cam, Race Engineering Adj Cam Sprocket, Crowlers, ARP head studs, and rod bolts. Walbro 255 HP pump and Kirban adj FPR, T-3. Centerforce II, KB subs and jack rails.