Cylinder 6 Misfire
02-21-2014, 03:19 PM
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Year: 2001
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Engine: 4.0
Cylinder 6 Misfire
Hello, seeing if anyone can help me out. I have a 2001 Cherokee sport 4x4 about 120k miles. Check engine light is on for a cylinder 6 misfire. So far I have replaced all spark plugs with champion, correctly gapped. Ignition coil, and 6 new fuel injectors. Once in awhile (typically when getting off of the interstate or highway) the check engine light will flash and the jeep sputters with little power. Once you turn the vehile off you can turn it right back on and it runs fine. no hesitation or rough idling. Anybody have similar issues? 
02-21-2014, 06:19 PM
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Year: 1990
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Good chance there's some carbon under one of the valves in #6.
2 things you can do.
Never a bad idea to add a can of BG 44K to a full tank of gas and run it to 1/2 tank. Fill again. Run to 1/8 tank.
This worked on my buddy's 99 after everything else he tried didn't work.
Pretty easy.
Get a cup of water, preferably something like a Dixie cup.
With the air cleaner off, hold the engine RPM at 2000 RPM or higher and dribble the water from the Dixie cup, which you've pinched to look like a spout on top, into the carb or throttle body. Go slowly and the engine will bog a bit. Stop and let it recover. Repeat until the cup is empty.
2 things you can do.
Never a bad idea to add a can of BG 44K to a full tank of gas and run it to 1/2 tank. Fill again. Run to 1/8 tank.
This worked on my buddy's 99 after everything else he tried didn't work.
Pretty easy.
Get a cup of water, preferably something like a Dixie cup.
With the air cleaner off, hold the engine RPM at 2000 RPM or higher and dribble the water from the Dixie cup, which you've pinched to look like a spout on top, into the carb or throttle body. Go slowly and the engine will bog a bit. Stop and let it recover. Repeat until the cup is empty.
02-21-2014, 06:38 PM
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I'd also recommend a simple compression test. On all cylinders. See where cylinder #6 is compared to the others.
The compression spec. for the 4.0 is 120-150 psi, with no more than a 30 psi variation between cylinders
The compression spec. for the 4.0 is 120-150 psi, with no more than a 30 psi variation between cylinders
02-24-2014, 08:45 PM
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Okay, thanks for the ideas. I'm going to check the compression in the cylinders and give a can of BG 44k a try. I've used two cans of sea-foam with out any difference.
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03-04-2014, 08:23 PM
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Update, compression is good in all cylinders. Tried Techron fuel system cleaner with no improvements. Actually seems to be getting worse, almost everytime I slow down from about 50mph or higher the check engine light flashes and I have to restart the jeep. 
03-04-2014, 08:34 PM
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Techron is noting compared to 44K. Try the water deal first.
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