temp up, einge idle increases

[Derick Cardenas]

this happened recently. before this about 8 months ago i replaced the thermostat.

traffic was real bad. it was night time and i noticed the temperature slowly increasing above normal levels. and the engine started going into higher rpm. i was on D mode. when i put the tranny in neutral, rpm went lower but temp is still up.



any ideas? is the cylinder head already cracked up or is there a problem with the transmission?:banghead:

 

[Bill Koonce]

The computer controls the engine RPM, both in drive and neutral. Is it throwing any MIL codes?



Just a guess, but you could have an intake leak that's causing an over-lean condition. In other words, you're getting more air than the computer knows about, and without any extra fuel, the mixture is lean. Lean mixtures tend to run hot, so...



Or it could be time for a new ECU... :boohoo:

 

[Derick Cardenas]

that's bad...new ECU

 

[EddieS'04]

fan clutch

 

[Bill Koonce]

The fan clutch could explain the overheating, but the two idle speeds are controlled by the ECU in closed loop mode. The ECU reads the flywheel timing signal, and adjusts throttle, spark and fuel delivery to maintain constant RPM.



Other sensors used in closed loop mode (like the oxygen sensors) might cause the strange idle speed in Drive. So can things that can cause erroneous sensor outputs, such as an intake leak. I'd check those first, and think about replacing the ECU only as a last resort, and only if it shows a clear fault that can't be fixed by new firmware.

 

[scott degroot]

Don't worry about the idle right now, be more concerned with the operating temp. Have you checked the coolant level to make sure that it is full?