plugs, wires, and 180 degree thermo

Originally Posted by AGT

mfuller...are you sure it will make it run richer. I mean really the only difference is the spring that allows coolants in at lower temps. I dont understand how it affects fuel/air mixture.

According to my service manual from Helm, yes. The Coolant Temperature sensor tells the PCM what the coolant temp is, and the PCM references several tables and adjusts fuel trims accordingly.

[AGT]

Yes but the coolant temp is not changed by the thermostat. It just changes when coolant flow is provided. When depends on which thermo you have. If you ran richer you should throw code or notice problems.

Originally Posted by AGT

Yes but the coolant temp is not changed by the thermostat. It just changes when coolant flow is provided. When depends on which thermo you have. If you ran richer you should throw code or notice problems.

I know. The theermostat stays closed until the engine coolant reaches a certain temperature, and then opens to allow coolant to flow back to the radiator to cool it down. Now, if the thermostat opens at a colder temperature, the PCM thinks that the engine still has some warming up to do, and dumps in more fuel to bring temps up. If you've ever monitored air/fuel ratios when your coolant is cold as compared to hot, you'll find that colder coolant temps (in general) equal richer air/fuel ratios....but they aren't enough to throw a Rich code.

[Cliff8928]

If you use too low temperature of a thermostat, you can trigger a Insufficient Coolant Temperature code though.