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  #16  
Old February 18th, 2013, 18:47
sandsgg sandsgg is offline
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Re: HELP! Yet another XJ Low, Rough Idle with Misfire Issue

Hmmm mines purple at the coil. Gonna have to clean that too..
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  #17  
Old February 20th, 2013, 10:31
tn_outside2003 tn_outside2003 is offline
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Re: HELP! Yet another XJ Low, Rough Idle with Misfire Issue

ONE single misfire at a light so far.
Possibly a result of very low idle.
I plan to pull the throttle body Saturday and re-clean the butterfly valve and the IAC.

Then I will look at TPS and MAP sensors.

Plugs and Injectors replaced...twice. And coil pack. And passed smoke test and fuel pressure test.

Will post up as situation progresses.
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  #18  
Old March 12th, 2013, 12:12
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dinorl007 dinorl007 is offline
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Re: HELP! Yet another XJ Low, Rough Idle with Misfire Issue

dont know if you checked it yet but it was mentioned ina earlier post check the grounds had same problem with a misfire jumping cylinders and was ground above the valve cover along the firewall is where they are all connected for the injectors try grabbing the harness and wiggling it with engine running and see if it getworse or better. all the gronds for the injectors share one wire with a rubber heat shield over them could have a bad connection hth
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  #19  
Old March 12th, 2013, 16:19
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Droopy76 Droopy76 is offline
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Re: HELP! Yet another XJ Low, Rough Idle with Misfire Issue

If you solve this, please post what you found. My brother has a 00 XJ. It has an extended crank, and misfires on cyl 5 & 6 at idle. Runs fine off idle. I've replaced the coilpack, plugs, CPS and swapped the injectors around. Still get the same misfires at idle.
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  #20  
Old March 12th, 2013, 17:11
cdrake261 cdrake261 is offline
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Re: HELP! Yet another XJ Low, Rough Idle with Misfire Issue

Quote:
Originally Posted by Droopy76 View Post
If you solve this, please post what you found. My brother has a 00 XJ. It has an extended crank, and misfires on cyl 5 & 6 at idle. Runs fine off idle. I've replaced the coilpack, plugs, CPS and swapped the injectors around. Still get the same misfires at idle.
Compression test? New champion copper plugs?
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  #21  
Old March 12th, 2013, 18:10
joe_peters joe_peters is offline
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Re: HELP! Yet another XJ Low, Rough Idle with Misfire Issue

Well, for those 2000-2001 XJ 4.0s that are cursed with "Hot Soak" or "Heat Soak"--the cylinder 3 misfire due to excessive engine heat on the injector, TSB NUMBER: 18-031-03; GROUP: Vehicle Performance; DATE: Sep. 05, 2003--the Chrysler fix is a JOKE. The only known down and dirty for sure fix is to put in a timer on the efan that will run the efan for about FIVE minutes after engine shutdown. Period.

The second issue is the mysterious multi-cylinder misfire, TSB NUMBER: 09-003-03; GROUP: Engine; DATE: August 1, 2003 applicable to XJs 1999-2001 and relates to the failure of the exhaust valves to properly rotate. It sounds like the OP used the MCCC--but the OP didn't post if he followed the inspection procedure in the TSB to determine if that was part of his problem.

Third, there is the LOW idle. Ok, lets simplify things for an easier discussion. An engine running LEAN will idle higher than an engine running RICH. If we accept that basic premise, then what could be causing the OP's engine to run rich? Could be those NEON injectors. I know of no recommendation for NEON injectors in the XJ past 1998.

Check the following information posted by rainman: http://naxja.org/forum/showthread.php?t=1085574

Last edited by joe_peters; March 12th, 2013 at 18:13.
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  #22  
Old March 12th, 2013, 23:45
ScienceguyXJ ScienceguyXJ is offline
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Re: HELP! Yet another XJ Low, Rough Idle with Misfire Issue

This may have been covered already... but have you thought about replacing your precat? Supposedly they can get pretty clogged over the years, 13+ years for yours probably, and it get too hot and cause misfires on hot days. Had this happen to mine once or twice on hot days and replaced the precat last summer and haven't seen misfires since.
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  #23  
Old January 6th, 2017, 20:07
bensimpson1981 bensimpson1981 is offline
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Re: HELP! Yet another XJ Low, Rough Idle with Misfire Issue

My 96 xj is currently doing the exact same thing?

Does anyone know what range the TPS should be reading when throttle is wide open?

My OBDII scanner has a live datastream feature and it reads absolute TPS 16.5% when throttle is completely untouched and maxes out at 77.4% with the throttle fully open.

Is this normal? Is it just the way the scanner is translating the signal from the sensor, it is a rather cheap bosch bluetooth scanner?
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  #24  
Old January 7th, 2017, 17:46
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Ecomike Ecomike is offline
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Re: HELP! Yet another XJ Low, Rough Idle with Misfire Issue

That may be a little low at WOT, but that alone would not cause the issues listed in this thread by the OP.

Quote:
Originally Posted by bensimpson1981 View Post
My 96 xj is currently doing the exact same thing?

Does anyone know what range the TPS should be reading when throttle is wide open?

My OBDII scanner has a live datastream feature and it reads absolute TPS 16.5% when throttle is completely untouched and maxes out at 77.4% with the throttle fully open.

Is this normal? Is it just the way the scanner is translating the signal from the sensor, it is a rather cheap bosch bluetooth scanner?
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