When the motor's cold it just doesn't want to be driven. It idles just fine on its own but it won't idle b/w 1000 - 1500 rpm without stuttering and bucking. It seems like it isn't reading slight throttle input properly when cold. If I hop on the gas it responds like it should. The result is that I can't drive it unless it hits a threshhold temp at which the problem suddenly disappears, almost like the computer is switching modes. Thats also when idle drops from 700 to 600 rpm. That leads me to think it's an open/closed loop problem, but what could be causing it? The engine responds to sharp throttle inputs and the like perfectly fine, acting weird only when I'm trying to take it easy when the engine's cold. I'm confused . Vader, anybody?

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'88 IROC 305 TPI
Gutted airboxes
160 degree T-stat
Advanced base TPS voltage
Relocated IAT sensor
Momo steering wheel
Ram-air setup coming soon
Flowmaster muffler
Taylor SpiroPro wires
Accel cap and rotor

 

Anyone?!!

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'88 IROC 305 TPI
Gutted airboxes
160 degree T-stat
Advanced base TPS voltage
Relocated IAT sensor
Momo steering wheel
Ram-air setup coming soon
Flowmaster muffler
Taylor SpiroPro wires
Accel cap and rotor

 

Has it just started doing this recently? This is the time of year when this oxygenated or reformulated gas hits the pumps.

 

If it's not the gas, then I'll bet it's your TPS. Those things will develop electrical "opens" along the resistive element inside them.

 

I've checked the TPS for an open condition but it checked out fine. The problem goes away as soon as the motor hits a certain temp. I know it isn't the gas, since it does it all year round. I'll try a new TPS anyway - it might solve the problem.

Does anyone have any other ideas?

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'88 IROC 305 TPI
Gutted airboxes
160 degree T-stat
Advanced base TPS voltage
Relocated IAT sensor
Momo steering wheel
Ram-air setup coming soon
Flowmaster muffler
Taylor SpiroPro wires
Accel cap and rotor

 

88,

It certainly sounds like the problem is with your open-loop operation when the oxygen sensor is cold.

If you think the TPS may be a problem, try moving the TPS lever when the engine is warming up. The lever can be moved independently from the throttle shaft on your engine. If you have a "flat" spot, you should be able to determine that by this test. If idle quality changes by advancing the TPS position when the throttle is closed, you are probably running a little lean. If the idle changes drastically, you may have a failing TPS.

You should also verify that the IAC system is clean, PCV and all vacuum hoses are intact.

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Later,
Vader
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