North American Turbocoupe Organization



Idle Speed Problems
Cullen Offline
Member
#1
I have an 85- 87 2.3 Turbocoupe engine I am having problems with in setting the idle.

Problems started a couple weeks ago when it started dying at stop signs. I got home to find out the connection going to the idle air by-pass solenoid had come off the sensor. However, just reattaching it did not cure my problem. Since, it will not idle down to around 900  to 1000 rpm. I checked my voltages and I set the middle terminal of the throttle position sensor to .9 volts. It will get down to about 1500 rpm and then just drop to dead zero rpm. I have changed the throttle position sensor but the new one will not maintain a voltage. I will set it to .9 and then when I tighten it it drops to zero. Put the first one back in but it will not idle down.

I have 5 volts to the throttle position sensor and when I rev the rpms up, the voltage on the middle terminal goes to maybe 1.2volts. 

I also have tried to change the idle stop Screw that the throttle lever rests on at idle. It helps keep the engine running but is just about to die it runs so slow and I have screwed that screw tight or until the spring no, longerallows me to screw it in more. I have read that the idle set screw should not be different than factory setting.

Seems crazy that the vehicle ran great up to the point the idle air by-pass solenoid connection came loose. I have replaced the solenoid since this was an old part on the engine.

Anyone have ideas why I am having such idle problems?

I have my timing set at 10 degrees BTDC with the spout removed.

Thanks for giving me direction.
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Jeff K Offline
Administrator
#2
Vacuum leak.
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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anasazi4st Offline
Senior Member
#3
(08-09-2020, 07:06 PM)Jeff K Wrote: Vacuum leak.

^^^^ What Jeff said.

I have mine set at .94 volts, but I don’t know that extra .04 makes that much of a difference.

One thing to consider: when you installed the TPS, are you installing it so that the rotary tang is in position over the throttle shaft blade—and did you then rotate the TPS CLOCKWISE into position? If not, that could be causing your idle speed problem.

I know you said you have been turning wrenches a long time. Just a suggestion.
Another proud dues-paying member.

1987 Turbo Coupe w/T5OD, 8.8 axle, grey smoke; most options. Got it in 1991 with 41K miles: 3 turbos, 2 heater cores, 1 T5OD full rebuild, 5 clutches, 1 head gasket, 2 Teves II ABS units, etc. later....
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Cullen Offline
Member
#4
I did look for vacuum leaks early on but did not test.
Good suggestions Togo back and check out.

Thanks.
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Jeff K Offline
Administrator
#5
Beat way to check for vac leaks is a smoke machine. Years ago I picked up a "party" smoke machine from Wally World for around $35. Made up some adapters out of heater and vacuum hoses so I could feed the "smoke" into the induction system is various places. It has worked well and simplified finding leaks.
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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Cullen Offline
Member
#6
I tried checking for leaks today. I used carburetor cleaner and made small spray patterns around hoses, tubing, the intake etc.
I would wait a minute before moving on to the next area. When I sprayed up under the intake plenum the engine immediately gained rpm and ran smoothly for a couple minutes. If this is truly a leak, it is where the positive crankcase vent connects to the bottom of the plenum, near the underside of the throttle body.
I like the idea. I used to use a bee smoker when trying to find air leaks in homes for energy conservation. You could see exactly where the air was traveling.
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Cullen Offline
Member
#7
I will try to locate the possible leak under the plenum tomorrow when I have more time.
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Jeff K Offline
Administrator
#8
Years ago the bung that connects the PCV hose to the intake plenum actually fell off. Must have lost its interference fit somehow. Glued it back in with JB Weld. Has been fine for at least 15 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
Reply

Cullen Offline
Member
#9
I have replaced the hoses, pvc valve and the fitting in the underside of the plenum.
And still, the 2.3 will not idle. It runs great above 1500 rpm but will start falling and pass right over 1000 and straight to zero.

I have tried 2 new throttle position sensors, a new idle air by-pass solenoid and fixed possible leaks in the pvc chain. I have also checked for leaks in the intake side from the mass air flow to the intake plenum.

I read another article regarding resetting the throttle position sensor and that mentioned that the ECU May take up to 75 miles of driving to reset itself to the new adjustments. Has anyone ever heard of this with these engines?
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Jeff K Offline
Administrator
#10
Did you replace the PCV valve with the correct Motorcraft EV127A part of some aftermarket junk? The only PCV valve that will perform correctly is the Motorcraft part.
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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