Rich snorty idle cured by unplugging the coolant temp sensor? - JeepForum.com
 
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post #1 of 2 Old 01-13-2017, 02:08 PM Thread Starter
8v-of-fury
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1998 ZJ 
 
Join Date: Nov 2015
Location: Orillia
Posts: 382
Rich snorty idle cured by unplugging the coolant temp sensor?

Why would this happen? Is my random bad running caused by something only when in closed loop?

The coolant sensor ohm'd out good at stone cold, never tried at op temp.

Could this be a bad 02 or just a faulty ECT?

PS. sorry for multiple posts, but directions of thinking changed and people who may know the answer dont check back in to the thread to see whats new.

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post #2 of 2 Old 01-13-2017, 04:28 PM
Uniblurb
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1996 ZJ 
 
Join Date: Jan 2012
Location: Central
Posts: 8,494
I did read your other post but was trying to find some more info first. I remember another member on here who forgot to connect their engine coolant temp sensor and he was pretty shocked to find his engine ran a whole lot smoother. Tried to search the post out and couldn't find it again.

The ECT provides input to the PCM in the form of voltage based on resistance/coolant temps. The PCM uses this input, along with input from other sensors, to adjust injector purse with along with engine timing. The fuel mixture is more rich when the engine is cold.

Believe I'd go ahead and check your ECT resistance at normal operating temps to make sure it's less than 1340 ohms. And believe you have access to the chart on what it should be according to temps.

I'd lean more towards the ETC being the problem rather than your o2 sensor. But you can unplug the upstream o2 sensor and see if your roughness smooths out indicating it may be faulty. Good luck.

96 4.0 ZJ Laredo, 2004 4.7L WJ Limited, 96 4.0 XJ (son's)


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