1996 Jeep Grand Cheeroke smokes black under throttle and idles rough?

G

GSD PAL

New member
The ECM uses the coolant temp readings to adjust injector on-time. With the engine cold the coolant temp sends the appropriate signal (resistance) and the ECM in addition to other inputs will adjust the injector on-time so that the mixture will be richer. AS the engine warms up the coolant sensor resistance changes and thus the ECM will then make a corresponding correction.
 
The guy told me that it was the coolant sensor and thats what the on board comp says. Im a mechanic but im old school I dont know much about fuel injection and computers but From what ive seen this could possibly affect it any insight would be awesome.
 
The problem you are experiencing is because the computers default setting if it doesnt see an accurate signal from the temp sensor is -40 degrees farenheit.
Basically no matter what the actual temp is your computer thinks it's buried under a snowbank in Fairbanks Alaska in January,so it naturally goes full rich.
Replace the temp sensor.
 
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