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  #1  
Old January 30th, 2013, 18:58
tn_outside2003 tn_outside2003 is offline
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HELP! Yet another XJ Low, Rough Idle with Misfire Issue

First: THANK YOU for taking the time to read this post.
I am a long-time member of JeepsUnlimited forums but new to . I am really in need so I came to , looking for new friends who may be able to help. This post is quite long because I wanted to be very thorough.

Second: YES….not only have I already (re)searched the topic…. But I have read just about every forum post and otherwise regarding the issue that I could find in forums and in google. I have several hours invested in reading previous posts.

BUT: I need YOUR help:

I have a 2000 Cherokee Sport, 4.0, 145,000 miles, mostly stock, OME lift, well cared-for. Every button, switch, lever, etc works as new. I am that guy that wants his XJ RUGGED….and FACTORY. Leather, sound system, cruise control, good tires, good lift, good roof rack, good disconnect, good slip yoke eliminator, etc. I USE my jeep. Scratches, minor dents and all....but exterior cosmetics aside, I am meticulous about keeping it in factory working condition.

Like MANY XJ’s…..I am having a LOW, ROUGH, idle and MISFIRES (codes). But it is new…and worse.

Here is the complicated history:

Ran fine. No worries.

Last summer it started up (what appeared to be) the cylinder 3 heat-soak misfire (indicated by rough idle and rough running after a heat soak on hot days. Ran fine after a minute or two and then it threw a flashing check engine light (once) and a misfire code on #3.

To verify, I swapped #2 and #3 injectors. The missfire followed the swap to #2. Hummm……So I put in a non-siemens, replacement injector from O’Reilly’s in CYLINDER 2, where I had swapped injectors and still gotten a misfire code. Replaced plugs with Champion (OEM) at the same time. I got some rough idle, but no engine codes.

A few weeks later I got a misfire code again. On #3. Heat of Summer. So I replaced THAT injector with some off-brand part from eBay. Heat-shielded the injector. Still idled a bit rough…but no codes.

Then, recently, (idle stayed rough since Summer…but no codes, January now), during an early morning, driveway idle warm up, I went to get back in the Jeep and it had thrown a CEL in the driveway. Misfire on #2, #3, and #5. This occurred during IDLE, during (or after) warm-up. I drove to work (35 miles, 80 miles an hour, hard-driving, non stop, every day, every other week) and it ran perfectly fine. Idled pretty rough at the stop light on the off-ramp.

Put in a new battery (it is winter now and it was cranking slow…fine now-just being thorough).

I figured my problems arose from mis-matched new injectors mixed with old injectors. So I ordered a whole set of the Bosch 4-hole “upgrade” from eBay. (NOTE: DO NOT DO BUSINESS with ULTIMATEINJECTORS on eBay….he is slow, holds your money for a week before shipping, and lies. Purchase from the guy in Tacoma, “leah7306.” VERY professional. Prompt. Etc.)

ANYWAY: I put in all 6 refurbished, flow-matched injectors and 6 new plugs. Old plugs smelled a little like gas and the ceramic around the contact was a little brown on all plugs…but no obvious carbon or oil fouling. Not white or burnt.
I pulled the (original) coil pack and checked resistance. It seemed consistent on the circuits…but I really could not “test” the pack. Boots look good. I put the same pack back on. No dielectric grease. Never used it on the XJ…why start now? The coil pack has springs that connect to the plugs. The springs were not oxidized and have worked perfectly for 12 years with no dielectric grease and Chrysler does not ship the XJ with dielectric grease in the coil pack. I am an OEM kind of guy (despite my use of the Bosch injectors…they seem to do no harm and are pre-made for a dodge (a neon I think).

I also pulled the cap off of the Cam Position Sensor (the sensor by the oil pressure sensor, on the side of the block) and cleaned the contacts and wiped it clean. It was clean before I started cleaning it. Just being thorough.

Reassembled and it started right up. Runs well. Drove to work (35 miles each way, 80 mph), for three days and calculated mileage to be at 14.9 mpg. Not bad for a roof rack, 235 75’s with aggressive tread, and 1” lift. So I think my Bosch O2 sensors are working right. I think.... I know I need NTK sensors…considering it.

It is still idling rough. And low. IMPORTANT (I think): it idles at 900 rpm when choked and purrs like a kitten. But as soon as it fully warms up the idle drops to about 400-500 rpms and is rough. I am pretty sure I am throwing misfire codes again (but I have not read it in three days).

I have thoroughly cleaned the Idle Air Control valve. I have sprayed a whole can of Mopar Combustion Chamber Cleaner into the throttle body and let it soak for 2 hours in a hot engine, then drove it at 4500 rpms, in 1st gear, 5 times to follow TSB to unstick any sticky exhaust valves.

So it has had:
Full set of rebuilt injectors
New battery
Cleaned IAC
New plugs
Cleaned CPS
Combustion Chamber Cleaner (basically a better seafoam treatment)

It runs FINE. It idles LOW and ROUGH. It throws misfire codes at idle sometimes. IMPORTANT (I think): When reversing, at idle or near idle, when fully warmed up, it runs more rough than normal and that is typically when it will throw a check engine light (no CEL since replaced injectors and plugs 4 days ago).

Exhaust smells normal. Some moisture drip (a good thing, right? Means cat is working, right?), No white/blue smoke. No black smoke. No antifreeze smell. No gas smell. Soot IS present around edges of tailpipe.

WHAT is wrong? What do I do now? Leak down test to check valves? Compression test? (not done yet), Bad Crankcase Position Sensor?, Bad MAP? Bad engine temp sensor (the one that controls fuel mixture when warm (essentially the choke sensor, I think)? A bad coil-pack? Bad heater on the O2 sensors (no O2 codes). Obviously I cannot just purchase all of these parts and throw them at the Jeep and hope it fixes the problem. Too expensive.

It seems to run fine. It is getting decent mileage (14.9), it idles rough WHEN FULLY WARMED, and idles MOST rough when idling in reverse. It has thrown misfire codes on #2, #3, and #5 so far. No CEL light for 3 days since new injectors and plugs.

What is going on here? It’s a jeep. It has always idled a bit rough. But these misfires at idle are new and the rough idle is a bit worse than “normal” and idle is a lower than it was. It used to dip to about 700 rpm when hot. Now 400-500 rpm.

My gut tells me that the fuel-to-air mixture is not right when warm. How can I check this? Where is the sensor that checks engine temp and determines choke...and how do I test it?

I am praying that just the right person finds this thread and can offer me advice. The local mechanics think I am insane. No code means its fixed (wrong!). All of the things I mention cannot be related (wrong!). They just want to assume it is fine until it throws a CEL again and then throw parts at it at $70 an hour until it works or I go broke.

Someone please come to my rescue!!!!! Please!!!!!


Thanks!!!
__________________
Jay in Tennessee
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  #2  
Old January 30th, 2013, 20:30
88trailcrawler's Avatar
88trailcrawler 88trailcrawler is offline
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Re: HELP! Yet another XJ Low, Rough Idle with Misfire Issue

Well, I am far from the right person. But I did read that whole post so I feel obligated to comment.

Have you checked fuel pressure?
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  #3  
Old January 30th, 2013, 20:37
WB9YZU WB9YZU is offline
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Re: HELP! Yet another XJ Low, Rough Idle with Misfire Issue

What codes is it throwing?
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  #4  
Old January 30th, 2013, 22:02
Renegade_Azzy Renegade_Azzy is offline
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Re: HELP! Yet another XJ Low, Rough Idle with Misfire Issue

Does it do this after it is run after being shut off for a short time? Like it has to heat up first and then it does this?

You may have the infamous heat soak, which I believe gets worse from those 2 damn pre-cats (which have to stay because of those 2 extra O2 sensors, and well, federal law). My wife's has it as well. Best fix i have seen is to put in a heat damn or shielding below the intake, which when it gets nicer is what we are doing here.

It would not hurt to do a leakdown and compression test if you have the tools to do both.
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  #5  
Old January 30th, 2013, 22:10
cdrake261 cdrake261 is offline
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Re: HELP! Yet another XJ Low, Rough Idle with Misfire Issue

I kinda have this problem as well...only I don't get the cylinder misfire code, just p1391...still haven't fixed it yet.
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  #6  
Old January 31st, 2013, 05:05
tn_outside2003 tn_outside2003 is offline
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Re: HELP! Yet another XJ Low, Rough Idle with Misfire Issue

Will post answers tonight.....
Off to work.
THANKS for replies.
JG
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  #7  
Old February 2nd, 2013, 09:25
xonlyj xonlyj is offline
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Re: HELP! Yet another XJ Low, Rough Idle with Misfire Issue

I have a '00 and had a intermittant code for misfire on # 3. Changed the injector and the problem went away-for awhile. I found my harness had chaffed on the back of the fuel rail. When I moved the harness to change the injector I cleared the condition and it settled back down after time to cause the same code. Applied some electricians tape and resecured to prevent the harness from sagging and has been fault free for months
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  #8  
Old February 9th, 2013, 12:30
tn_outside2003 tn_outside2003 is offline
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Re: HELP! Yet another XJ Low, Rough Idle with Misfire Issue

Sorry for the delay. I had to order a code-scanner so I could efficiently monitor codes.
AND I decided to replace the coil because it is the first question everyone asks.

I have been driving it daily for two weeks. I have an intermittent code (meaning I have driven for three days with no codes..then suddenly I get two in a row in one afternoon).

The code is P0305 (misfire on cylinder 5). I have not done a compression test because I assume a bad head would be a constant misfire and would not run correctly for three days with no codes.

I tried to test fuel pressure but the O'Reilly's gauge was broken....twice. But again...low pressure would give a more frequent code, right? Pumps work or not....they don't vary pressure....or am I totally wrong about this?

My scanner shows no codes with the emissions (O2 sensors).

The jeep is still idling low and rough.

I am not sure what direction to go in now.

Any help would be appreciated.

Thanks,

JG
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  #9  
Old February 9th, 2013, 12:31
tn_outside2003 tn_outside2003 is offline
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Re: HELP! Yet another XJ Low, Rough Idle with Misfire Issue

Oh--this is NOT a heat-soak issue. That happens sometimes in Summer....but this is not the same issue.
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  #10  
Old February 18th, 2013, 14:52
tn_outside2003 tn_outside2003 is offline
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Re: HELP! Yet another XJ Low, Rough Idle with Misfire Issue

Update:
A lot of these threads just stop part way through the repair process.

I checked the indexing of the Cam Position Sensor (toothpick alignment) but it was perfect and did not require adjustment.

Took it to a local garage and paid $88 to have the Crank Position Sensor replaced, a smoke test on the vacuum system, verify cam position sensor is reading "0" on the scanner when running, and test fuel pressure. A TOTAL bargain no matter how you look at it.

After one test drive I have no codes and no misfires. Still idles around 600 instead of 900 and a little rough...but not like it was. It was shaking the whole jeep.

Could this really have been a crank position sensor?
I am not convinced yet.

Consider that CPS tends to cause hard start or no start.

I was having misfires, exclusively. Random misfires (P0300, and various cylinder misfires (P0302, P0304, P0305). And CEL on and sometimes flashing.

I will post up as the week progresses. It is my turn to drive this week. 32 miles each way at 80 miles an hour.

Even though no one is still replying to me and I am on my own here...at least other people will be able to reference this thread and hopefully it will help them.
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  #11  
Old February 18th, 2013, 14:56
tn_outside2003 tn_outside2003 is offline
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Re: HELP! Yet another XJ Low, Rough Idle with Misfire Issue

Oops:
Duplicate.

Last edited by tn_outside2003; February 18th, 2013 at 14:56. Reason: Duplicate
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  #12  
Old February 18th, 2013, 15:18
cdrake261 cdrake261 is offline
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Re: HELP! Yet another XJ Low, Rough Idle with Misfire Issue

Quote:
Originally Posted by tn_outside2003 View Post
Even though no one is still replying to me and I am on my own here...at least other people will be able to reference this thread and hopefully it will help them.
I'm reading along, not an expert at fixing jeeps yet
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  #13  
Old February 18th, 2013, 17:37
SBpunk SBpunk is offline
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Re: HELP! Yet another XJ Low, Rough Idle with Misfire Issue

Sorry didnt read all the replies but this is what I did on my 98'. Take it for what its worth. I spent probably 300+ on a 60$ part.

First off check, clean and replace if necessary all of your grounds. Then test your battery under load.

Go to Checkers or Napa and get a spark plug tester or if you're ballsy get a flat head screwdriver and test your spark. Yellow is bad and white is good. If everything is good then move on. If not try buying a new coil, dist. cap and rotor. They're not that expensive.

Next up run a check on your TPS. Its in the back center of your throttle body. Gotta google this one because I don't remember how. Its pretty easy tho with back probing. If it comes up faulty go to the dealership or WeRMopar.com (much cheaper). DO NOT buy a knock off sensor. I did this and it had my chasing my tail like a moron for almost a month now. Anyway it sounds dumb but I was having random misfire codes and this solved it. Anytime these things get wet they short out.

Lastly because its the most expensive is make sure you have the right injectors. Shouldnt be more than 19lb injectors. Any more than that will cause misfires and you'll eat up your gas fast.

Like I said though I didn't read thru all the posts so if I'm repeating I apologize. TPS's are horrible and I hate them... lol
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  #14  
Old February 18th, 2013, 18:30
sandsgg sandsgg is offline
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Re: HELP! Yet another XJ Low, Rough Idle with Misfire Issue

If yellow is bad and white/blue is good, what is purple
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  #15  
Old February 18th, 2013, 18:42
cdrake261 cdrake261 is offline
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Re: HELP! Yet another XJ Low, Rough Idle with Misfire Issue

Quote:
Originally Posted by sandsgg View Post
If yellow is bad and white/blue is good, what is purple
between white and yellow...otherwise fair
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