gmrulz4u Posted May 2, 2003 Report Share Posted May 2, 2003 Even after replacing my coils, my engine is still running pretty rough. I hooked it up to my AutoXray Scanner tonight to see what I could find, and I could really only notice 2 things I THINK are strange: 1) My MAP Sensor voltage would rise by itself when I was at a complete Stop and idling in Park. It would go as high as 2.20 volts, which from what I believe, indicates LOW vacuum. 2.20 volts would normally indicate at least SOME gas pedal pressure... 2) I'm not exactly sure if this even IS a problem, but I noticed that the MAT(Manifold Temperature Sensor or Intake Air Temperature) Sensor doesn't change as often as I thought it was supposed to. Some sensors are changing their data like every single second, but the MAT data just was staying at 86 degrees F' for the LONGEST time! I'm not sure if this is normal or not? It seems like it would change by a degree or two only every couple minutes, whether I was sitting idling or moving at 35 MPH. That's all I could really see on the scanner so far... Anyone with any comments? I know you guys aren't GM Master Techs or something, so I don't want anyone to think I'm looking for BIG answers:) I understand we don't all know EVERYTHING! Quote Link to comment Share on other sites More sharing options...
Slade901 Posted May 2, 2003 Report Share Posted May 2, 2003 If your Air Temperature Sensor or (common names) Manifold Air Temperature Sensor, Air Charge Temperature Sensor, Inlet Air Temperature Sensor, Throttle Body Temperature Sensor, Vane Air Temperature Sensor does not change its temperature when the engine is running, then it probably needs a replacement. I had a similar issue with it before. I tried finding a replacement for it at Napa, Autozone, Advanced Autoparts, etc., but they don't carry it and suggested to go a dealer. Instead, I removed the Air Temperature Sensor and noticed that the tip of it is covered with hardened carbon and I scrape it off as much as I can and connected it back in and this time the Air Temperature Sensor is working again. Quote Link to comment Share on other sites More sharing options...
gmrulz4u Posted May 2, 2003 Author Report Share Posted May 2, 2003 Thanks for the info! Do you happen to know just how RAPIDLY the MAT Sensor's temp. is supposed to change? Because I think mine is WAY TOO slow to respond! This morning driving to work, it stayed at 57.2 F' for over 5 minutes of Stop and Go Driving!? THANKS AGAIN:) Quote Link to comment Share on other sites More sharing options...
Slade901 Posted May 2, 2003 Report Share Posted May 2, 2003 MAT Sensor is suppose to change just around 2-3 minutes of IDLE. While driving, the MAT Sensor temp should have already changed. I would definitely suggest removing the MAT Sensor and clean off the gunk at the tip and see if that makes a difference. Quote Link to comment Share on other sites More sharing options...
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