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Unread 02-22-2002, 01:41 PM   #1
JEEPIN DAKOTA
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Join Date: Feb 2002
Location: San Diego, California
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MISSING ON#3 AND #6 CYLINDERS

I'VE GOT A 85 JEEP CJ-7 258 I6 BASICALLY STOCK. IT HAD THE SAME PROBLEM BEFORE AND AFTER A REBUILD. I'VE CHANGED OUT BOTH OF THE COMPUTERS,CHECKED FOR VACUUM LEAKS, REPLACED THE DISTRIBUTER, CHECKED OUT ALL OF MY CONECTIONS ON THE WIRE HARNESS, CHANGED THE CARB,CHECKED THE TIMING, DONE A TUNE UP,AND CHECKED THE COMPRESSION. CAN ANYONE HELP OR AM I DOOMED WITH MISSING FOR EVER. BY THE WAY MOST OF THESE THINGS WERE SUJESTED BY THE DEALER (AFTER A DIAGNOSIS) AND OUT OF FLUSTRATION.

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Unread 02-22-2002, 02:07 PM   #2
Jeep Daddy
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What was your compression? It should be about 150 psi with no more than 10% variance. Is it any lower on 3&6? Are you sure it is missing on 3&6? Did someone put it on a scope? Do you feel it when you drive it? or just when it idles?

What did your tuneup consist of? Plugs? Wires? Cap? Rotor? Are you sure you have the wire back in the correct firing order? What about your timing chain. If it is real hard to start and runs with about 1/2 power, the chain may have jumped a tooth.

The only thing the computer does is adjust the carb via the O2 sensor after the engine is warm. Look down the carb and see if the stepper motor is actuating the 2 metering pins. They should be going back and forth at idle.

Are you sure that when you installed the plugs you didn't get grease on them or some other crud? That will foul things up.

Wish you luck. Keep us posted after you've tried everything. Let us know what the solution is after you fix it too.
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Unread 02-22-2002, 02:18 PM   #3
JEEPIN DAKOTA
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I'M NOT REALLY GOOD WITH EXACT NAMES BUT CAP, ROTAR, PLUGS (CLEAN), WIRES, O2 SENSOR (CLEAN), ALL CYLINDERS SAME COMPRESSION, MANIFOLD NO LEAKS, ONLY WHILE IDLEING BUT I THINK THERE IS POWER LOSS. EVERY THING IS EXACTLY THE WAY THE HAYNES MANUAL SAYS TO DO IT. I'VE BEEN TINKERING WITH CARS AND MOTARS SINCE MY DAD WOULD LET ME IN THE GARAGE WITH HIM (AGE 9-10) AND THIS JUST COMPLETELY STUMPS ME. EVERY THING IS THE WAY ITS SUPOSE TO BE.
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Unread 02-22-2002, 09:40 PM   #4
Jeep Daddy
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How many miles on the engine? As I said before, did you scope it to determine it is missing on 3 and 6? or did you let it run and just pull a plug wire? When you do that on 3 and 6 do you notice a big difference? (one at a time) If no difference, you know your deffinately missing on those cyls. If it does change it a lot then you are probably not missing spark, but probably have a hi-voltage leak somewhere. Probably the cap and rotor.
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Unread 02-23-2002, 09:59 AM   #5
Guy Hollister
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What makes you think its missing on 3 n 6 ? you have virtually a new everything !

g
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Unread 02-25-2002, 12:15 PM   #6
JEEPIN DAKOTA
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Yes, I did scope it and it was intermitently missing on 3 & 6. It was not a constant miss like if you pulled a plug wire. More like if you would pull a plug wire off about every 4-5 sec. then replace the wire, 4-5 sec. pull the wire. There is only about 5000 to 8000 miles on the rebuilt motar but it missed the day I put the new motar in and fired it up. I'll check out the distributer again but everything there is new, less than 1000 miles.
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