The hestiation has been going for about 10,000 miles. The A/F ratio is within specs. I thought previously that it was simply a minor warm up issue but the engine stumbles badly. (Not the typical minor irregularity of a cold motor warming up.) This is a distinct point at 130F where the timing advance all of sudden works again. Below 70F the timing advance works fine too as it does when you are off throttle regardless of the engine temperature. On very cold days the motor runs fine but when the cooolant reaches 70F it's as if a switch is triggered or signal is lost. This signal again returns at 130F. I think somewheres I'm losing a signal to the ECU when the coolant is between 70-130F and just on throttle. The only things in theory I can come up with is a temperature sensitive short in the harness or an uncharted switch in the circuit that has gone bad or a corrupted timing map in the ECU.
08:44:15 12/16/07
