2003 Chevrolet Tahoe

Engine Performance problem
2003 Chevy Tahoe V8 Four Wheel Drive Automatic 142000 miles

Hey Guys, love the website. I have a 2003 CHevy Tahoe 5.3 Z Flex Fuel. Troube began with a CEL/SES light. Few days later Tahoe started idling rough, varying idle speed, and on cold start may die if left idling during warm up. On a cold start, I also notice occasional knock in the engine, and if I slightly rev engine or place in drive before waiting for engine to warm up, it is VERY apparent. At first, it would idle better after warm up, but now it idles rough regardless, however, the knock does go away after it is warmed up. Only codes it spit out are P0174, and P0171 bank 1 and 2 lean. I cleaned the MAF sensor, and didn't notice a significant change at all. Should I go after new MAF, new O2 sensors? Thanks for your help.

Shayne J. Benoit
Spring Cityl, Tennessee
January 5, 2010.

Start by checking for vacuum leaks that would allow extra air into the intake system (thus a lean mixture) Also, I would check the ambient temp sensor. If it is telling the computer it is warmer than it actually is, that will cause a lean mixture too. Usually when an O2 sensor or MAF is bad, they set their own code.

Let me know what you find.


Any more specifics on the ambient temp sensor as far as location on viehicle. There is one in grill, but I think it feeds the rear view mirror thermometer.

Jan 5, 2010.
Could the ambient temp sensor also be called the Air Change Temperature Sensor?

Jan 5, 2010.
See if this helps and let me know.


I discovered that the IAT (Intake Air Temperature) sensor I inquired about is integrated into the Mass Air Flow sensor on many Chevy's. The harness on the MAF has a Black and Tan wire that attaches to the IAT sensor. If this has failed, JET has a Intake Air Temperature Sensor Relocation Kit 61635 for 2003 Chevy Tahoe

equipped with a Mass Air Flow Sensor that has a Integral Intake Air Temperature Sensor. The Intake Air Temperature Sensor is a negative coefficient (NTC) thermistor that is used to sense air entering the engine. The computer utlizes the IAT to adjust the air/fuel ratio in accordance with air density. It’s also used to modify spark advancement and acceleration enrichment. This kit allows the IAT to be relocated away from the hot engine compartment so the computer can get a more accurate reading of ambient air temperature thus improving

Feb 14, 2010.