A short history first. My 95 GT was experiencing the typical hanging idle, rough idle problems this past winter. I installed new ECT and ACT sensor's from NAPA in February. That seemed to fix my hanging idle problems, however my cold idle was still pretty rough. Idle improved as car warmed up. My cold starts also seemed quite long (engined turned over 10-12 times before firing - warm starts were fine) and the car usually bucked once or twice driving away.
Now the car was running pretty good in general, but the cold start/idle issue was buggin me because I figured it should be better than it was. After much research of various books/internet threads, it seemed to me that a bad ECT would be causing my cold engine problems, even though I had just installed a new one in February. I should also mention that NO codes or CEL lights had occurred.
Yesterday, I pulled the connector for the ECT sensor and checked the cold resistance with a DMM. The resistance was about 5000 ohms too high for the temp. Not off alot considering the range the sensor puts out, but I decided to investigate further. I also had another old Ford ECT sensor from a different car that I checked, and it was within spec. I pulled the NAPA sensor and placed both ECT sensors in the freezer. After 10 minutes I checked the resistance on both ECT sensors. The NAPA sensor was reading WAAAAY less resistance (30,000 ohms) than the old Ford sensor (less resistance means the sensor is saying the temp is warmer). Hmmm, might be on to something here...!!!
I then check hot temp's by dropping both sensors in almost boiling water. The resistance levels on both sensors was almost identical. BINGO!!! PROBLEM SOLVED!!!! When my car was cold, it started/idled bad because the 3 month old ECT sensor from NAPA was telling the computer that the engine was warmer than it really was, therefore the fuel ratios were screwed. Once the car warmed up, the ECT sensor was telling the computer the correct information and the car ran like new.
I installed my old used Ford ECT sensor and the car started almost instantly and idle great from cold all the way to normal operating temp's. No bucking either when driving just after cold start
In summary, JUST BECAUSE A SENSOR IS NEW, DOESN'T MEAN THAT IT IS GOOD! Stupid friggin NAPA sensor!!!! From now on, it's only quality Ford sensor's for me!!!
Hope this helps someone in the future.
Now the car was running pretty good in general, but the cold start/idle issue was buggin me because I figured it should be better than it was. After much research of various books/internet threads, it seemed to me that a bad ECT would be causing my cold engine problems, even though I had just installed a new one in February. I should also mention that NO codes or CEL lights had occurred.
Yesterday, I pulled the connector for the ECT sensor and checked the cold resistance with a DMM. The resistance was about 5000 ohms too high for the temp. Not off alot considering the range the sensor puts out, but I decided to investigate further. I also had another old Ford ECT sensor from a different car that I checked, and it was within spec. I pulled the NAPA sensor and placed both ECT sensors in the freezer. After 10 minutes I checked the resistance on both ECT sensors. The NAPA sensor was reading WAAAAY less resistance (30,000 ohms) than the old Ford sensor (less resistance means the sensor is saying the temp is warmer). Hmmm, might be on to something here...!!!
I then check hot temp's by dropping both sensors in almost boiling water. The resistance levels on both sensors was almost identical. BINGO!!! PROBLEM SOLVED!!!! When my car was cold, it started/idled bad because the 3 month old ECT sensor from NAPA was telling the computer that the engine was warmer than it really was, therefore the fuel ratios were screwed. Once the car warmed up, the ECT sensor was telling the computer the correct information and the car ran like new.
I installed my old used Ford ECT sensor and the car started almost instantly and idle great from cold all the way to normal operating temp's. No bucking either when driving just after cold start
In summary, JUST BECAUSE A SENSOR IS NEW, DOESN'T MEAN THAT IT IS GOOD! Stupid friggin NAPA sensor!!!! From now on, it's only quality Ford sensor's for me!!!
Hope this helps someone in the future.