Cold Start Idle Problem

the truck in cold weather, after about 3-5 minutes the idle starts fluctuating by about 300-500 RPM's up and down at regular 1-2 second intervals. It is almost as if someone is depressing the accelerator and then letting off. It does this until the truck has been running for about twenty minutes and then it runs fine. Please advise, thanks.

I had the same problem with my '89n 22RE, it turned out to be the thermostat wasn't functioning properly. I remember distincly. Replace the thermostat, make sure your hoses are good, and fill the radiator and report back!!

Dave

starting the truck in cold weather, after about 3-5 minutes the idle starts fluctuating by about 300-500 RPM's up and down at regular 1-2 second intervals. It is almost as if someone is depressing the accelerator and then letting off. It does this until the truck has been running for about twenty minutes and then it runs fine. Please advise, thanks.

1-2 second intervals sounds kinda frequent, but it could just be the fan turning on. i believe the 94's were still running 22re's. in my '89 22re, i notice a definite change in idle speed (500 vs 800) depending on whether the fan clutch is engaged or not. of course this is more like on a 1-2 minute interval rather than a 1-2 second, but maybe the fan clutch is bad or something.

you may also want to clean out the throttle body. i had a problem with a very high high-idle and a very low low-idle a couple of months ago. a simple cleaning of the throttle body brought everything back to normal.

mike

I replaced the thermostat and the problem remains. Do you know what role the throttle body plays with the coolant? thanks for your suggestions, -Miles

I removed the air intake hose to the intake manifold and sprayed the throttle plate. Needless to say it was pretty gunked up. I'm sure this helped but it did not cure my problem. Are there any other areas of the throttle body I can clean easily?. Several questions arise, could the EGR valve need replacement? and could there be a problem with coolant circulating in the system/throttle body? Thanks for your suggestions so far, -Miles

Throttle Position Sensor most likely

starting the truck in cold weather, after about 3-5 minutes the idle starts fluctuating by about 300-500 RPM's up and down at regular 1-2 second intervals. It is almost as if someone is depressing the accelerator and then letting off. It does this until the truck has been running for about twenty minutes and then it runs fine. Please advise, thanks.

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I highly doubt it's the Throttle Position Sensor or EGR, the EGR kicks in at crusing speeds, and if the TPS was bad it would run extremely lean. Just replace the thermostat like I said. I bet that would do it.

Dave

I replaced the thermostat this past weekend. I replaced it with a NAPA thermostat. This did not solve the problem. I am thinking that it is something related to the cooling system also. Today after I started it up in 50 degree weather I did not expect it to idle high as though it was a 20 degree day. Do you know anything about the two stage thermostats available? Would one help? I replaced mine with the original style (one stage). Also I think the heater is playing games cold air to suddenly hot air when the heater is on, not the gradual warming I would expect. The air gets hotter as I accelerate. Let me know your thoughts, thanks -Miles

thermostat. This did not solve the problem. I am thinking that it is something related to the cooling system also. Today after I started it up in

50 degree weather I did not expect it to idle high as though it was a 20 degree day. Do you know anything about the two stage thermostats available? Would one help? I replaced mine with the original style (one stage). Also I think the heater is playing games cold air to suddenly hot air when the heater is on, not the gradual warming I would expect. The air gets hotter as I accelerate. Let me know your thoughts, thanks -Miles

This may not help your problem, but.... Someone posted a link to a Toyota TSB for 83 - 84 pickups... I don't know the link, unfortunately, but I can tell you that they recommended if you didn't want to buy one of the dual-stage thermostats, you could take the original style one out and drill a small hole or two in it and that would keep the cold water rush from the heater core from closing the just-opened thermostat... I've used this trick on a BMW 735i that I could not get to 'burp'.. works like a champ. Going to do it today on my '83 Celica.