coolant temp sensor/misfiring

So my 95 xj with a 4.0 and 201,000 miles has started misfiring when I start it for the first start of the day, it goes away if I floor it or drive it around the block ,and runs fine for the 67 miles I drive after that..Tonight it was misfiring bad it barely left the parking lot, floored it down the street and it cleared up..Then the check engine light came on , code 22 , for the coolant temp sensor...Can these be related, like the cts causing it to run lean or rich?..Hopefully it is cause its an easy fix..It also seemed to be shifting strange and idling weird, when I got close to home byt that could have been my imagination..

Im gonna check it when I wake up..How do I check the ohms I have the multimeter to check it but never used one and dont know what to do,Like what prong do I place on what pin, etc...

And how long does it take for the truck to "warm up", I dont know because all I have is the idiot light..

sounds like it is running rich and causing it to "load up" by having such a rich fuel mixture the spark plugs cannot fire. start it, run for a lil while with it missing and do not clear it. turn it off and pull the plugs. if black and wet its too rich if they are white too lean. should be a light gray with some variance allowed

i pulled 1 plug, closest to the firewall,it is grey .I started it it was worse then ever ,but went away after like 10 seconds..I let it run for like 5 minutes...would all the plugs be black if it was running too rich because of say that coolant temp sensor ,that the light came on for?im sure with my luck they are seperate problems though and probably both are a pain in the ass

meant to say i ran the engine for 5 minutes before i pulled the plug..was that too long/burned any soot away? cuz it only misfired for a few seconds..sorry about all of the dumb questions i am new to working on cars but would like to learn as much as i can

Sounds to me like a leaking fuel injector--you shut the engine off, fuel leaks into the manifold and pools there or in a cylinder. Start the engine it runs rough until the fuel can be expelled, then runs fine until you shut it off again.

You don't seem to be getting a misfire code so the plugs are firing but the mixture is screwed up in one or more cylinders.

Fuel pressure gauge is probably what you are going to need here, find out how fast the pressure is bleeding off.

When trying to diagnose, you need to pull ALL the plugs--keep them lined up by cylinder--and compare ALL of them to each other and a chart: http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqread.asp

is it true you can rent them from autozone?

ak95xj said:

is it true you can rent them from autozone?

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Most of the chain parts stores will rent them.

I am gonna be looking into this

If I let the fuel out of that valve on the fuel rail before I park it for the night will that help

Im mostly just scared of the leaking gas washing oil out of the cylinder or somethin

i would still check the coolant temp sensor(variable resistor). not sure where it is on the 95, as its on the side of the block under the exhaust manifold on my 89.

set the multimeter to ohms, disconect the 2 pin wiring harness of the cts and put the leads of the multimeter to the pins on the cts harness. if you do a search you should be able to find a chart/table that compares the resistence values to the engine temp. the resistor changes values as the engine temps increase which allows the pcm to make changes to the a/f ratio mixture. if the sensor reads infinite or zero on a cold engine it may send too much fuel at start up


you might find the chart/table at www.lunghd.com

its right on top of the thermostat housing on mine,replaced that yesterday,the old one i took out said 400 or something like that , the new one said infinate...

ak95xj said:

its right on top of the thermostat housing on mine,replaced that yesterday,the old one i took out said 400 or something like that , the new one said infinate...

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did it help/fix the cold startup problem???

well I started it cold maybe like 5 times and so far it hasnt given me any trouble,so I guess Ill see how it works out the next few days.I also put a can of injector cleaner in the fuel tank..The morning after the light came on for this, when I went to start it to go to the parts store was the worst I ever seen the jeep,took like 10 tries to get it running badly ,and opening the throttle just wanted to kill it,it also backfired out of the throttle once..But then it just cleared up and I was on my way

About a month ago the gasket for the water pump started leaking badly , so it was definately running low on coolant a few times ,and the temp light came on a few times ,from it leaking out on the highwaym, before I fixed it,so maybe that thing got fried from that...

i also cracked the thermostat housing in half when i screwed the new one in..i was thrilled about that..i was thinking "hmm this is the easiest repair ever" *CLINK*

A bad coolant temp sensor will definitely cause the symptoms you described. The engine computer uses the sensor reading to determine if the engine has warmed up. If the sensor is bad the computer will think the engine is super cold and run very rich.

Most of the sensors are ignored on wide-open throttle. I don't know if the coolant sensor is also treated that way, but it would explain why the engine ran fine with your spirited driving

Just go to autozone and get another sensor for $15. It's the sensor sticking out the top of the aluminum housing at the top radiator hose