XJ Diagnosis help

[saburai]

Naxja

I totally agree with bobDog.....excellent place to get advice. 99% of them are great folks and the other 1%....well not so good.:coffeedrink:

I'm a member. TONS of info. Mostly good folks.

For me there is more of a sense of camaraderie here as well as less pontificating:smiley_drive:

 

[wardrow]

Do you have access to an Oscilloscope?

 

[saburai]

Nope, no scope. I'm gonna spend the morning tracking it down...

 

[jsolorza]

do you have a scanner with live data? also how good is your spark orange or blue, also have you tried starting your jeep with the throttle slightly depressed in case your iac is sticking?

 

[MuckSavage]

Saburia,

I had the exact same problem that you describe ('96 XJ). Long story short. It was the Coolant Temp Sensor (the one on the t-stat housing). My bro-in-law was behind me one day when I started it & saw black smoke upon finally starting. When I described the condition. He suggested that sensor. I told him it didn't throw a code, but he still nailed it. Apparantly, it won't throw a code, the sensor's still working, just telling the ECM the wrong temp. & (mis)adjusting the amount of fuel accordingly.

Good luck, hope it helps....

-Muck

 

[jcdespaux]

Maybe check throttle position sensor,

 

[dbthomson]

yeah I would look at the tps or iac( idle air control valve) just off the throttle body, pull the iac off and clean it with throttle body cleaner and give it a whirl...also the cps will kill spark

 

[bldeagle10]

agreed, it is one of those random sensors going out, could be coolant temp as previously stated, I had this issue in a dodge a few weeks ago, rough idle, no start conditions onless at WOT, coolant temp sensor is necessary for the ECM to regulate air to fuel ratio, if that is off it can cause issues obviously. for the dodge it was only a $20 part so I don't see it being to expensive for the ole 4.0, could also be TPS or IAC, not sure of the exact symptoms of those because I haven't run into any issues with mine yet. I would go through and check as many sensors as you can. good luck man, took me forever to figure out the issues with my jeep, (sticky valves, needs a head rebuild sometime in the future)

 

[Black Dog]

OP-I may have missed, but does it turn over at all when you try to start it, or is it just dead silence with absolutely nothing? Some times my '99 heap won't start for me, I hear the started solenoid engage but the starter won't go. I put it in gear and rock it a bit them jam it back into park and that is enough to move the starter off the bad spot and it fires up like a beaut.

Right now though my heap turns over but doesn't fire. This is my problem of the week.