88' 4x4 Pickup-V6
Join Date: May 2019
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Good question. Yes, I have checked the ECT resistance at both cold and at operating temp. If fact, with the connector unplugged, I jumpered the connector with different size resistors to mimic a hot engine which had not effect on this idle issue.
Most of the smaller dia. vacuum lines have been replaced. I have also checked for leaks using a low flow propane around the various joints and hose connections.
I have removed and cleaned the throttle body. In this old version of the 3VZE, the IAC is incorporated into the throttle body which I cleaned as well. I did suspect this for a while, but that would imply it is related to Engine Temp and it is not. Also can’t find a replacement throttle body.
EGR tested good.
As stated in the original post, idle speed is directly related to the outside air temp:
• Start engine on a warm afternoon at the end of the work day (outside temp at 70°) = idle low.
• Engine at temp, driving down the road on a cold day (outside temp at 40°) = idle high, fuel cutoff with brake on at stop sign.
• Engine at temp, park Pickup for 15min in garage (engine compartment air heats up), drive again (outside temp at 40°) and idle is low for the first couple of minutes, but after that first mile, the idle high & fuel cutoff with brake on (air entering air filter is cold).