88 yj running rough - JeepForum.com

 
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post #1 of 15 Old 04-26-2013, 01:44 PM Thread Starter
sloopie
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1988 YJ Wrangler 
 
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88 yj running rough

I have an 88 yj with 4.2 and Weber 32/36 carb. It has the nutter bypass. Under load it is missing and has got progressively worse in the past few weeks. It used to happen at higher rpms. Now it does it at any rpm. I put née cap and rotor plugs and wires. Along with a new fuel filter. It has a new coil also. Could it be the original exhaust plugged up or off time? Any help appreciated.

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post #2 of 15 Old 04-27-2013, 10:23 AM Thread Starter
sloopie
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No?
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post #3 of 15 Old 04-27-2013, 11:35 AM
Que89YJ
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It is only missing under load?
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post #4 of 15 Old 04-27-2013, 12:45 PM
Old4X
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Check for vacuum leaks, especially under the carb and at the intake to head mount.

418 miles on 19 gallons of gas. Can't beat the BBD !
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post #5 of 15 Old 04-27-2013, 01:44 PM Thread Starter
sloopie
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Yes only under load. I'll check for leaks with some carb cleaner now.
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post #6 of 15 Old 05-09-2013, 09:02 PM Thread Starter
sloopie
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No vacuum leaks. Maybe my ICM?
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post #7 of 15 Old 05-09-2013, 10:12 PM
Old4X
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What is your plug gap?

Are you using the Team Rush upgrade?

Skipping under load can indicate high voltage breakdown if vacuum is OK. Also, have you looked at the timing marks (with timing light) as you increase RPMs? Is it smooth or jumpy?

Ported or manifold vacuum for vac advance?

418 miles on 19 gallons of gas. Can't beat the BBD !
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post #8 of 15 Old 05-09-2013, 10:31 PM
JeepingJustin
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Quote:
Originally Posted by old4x View Post
what is your plug gap?

Are you using the team rush upgrade?

Skipping under load can indicate high voltage breakdown if vacuum is ok. Also, have you looked at the timing marks (with timing light) as you increase rpms? Is it smooth or jumpy?

Ported or manifold vacuum for vac advance?
x2
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post #9 of 15 Old 05-10-2013, 06:57 AM Thread Starter
sloopie
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Vacuum advance is ported. Have not checked timing and no team rush.
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post #10 of 15 Old 05-10-2013, 09:29 AM
Old4X
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Re tune it for manifold vacuum and see if the problem is still there.

You can not run over .035 plug gap without upgrading wires, cap and rotor.

418 miles on 19 gallons of gas. Can't beat the BBD !
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post #11 of 15 Old 05-10-2013, 11:12 AM
dtn8tr
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After all is said and done, upgrade your cap, rotor and wires like Old4x said. That original 18,000volt coil sux. I noticed an immediate improvement when I changed all that out.

1997 TJ, 5" IRO front with 4.5" HD IRO WJ rear, 35x12.5x15 Mickey Thompson MTZ, JKS disconnects
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post #12 of 15 Old 05-10-2013, 02:08 PM Thread Starter
sloopie
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I've got new cap, rotor, plugs, coil and wires. Also new fuel pump and filter. Tried rejetting the Weber 32/36 but didn't help. My plug gap is right at 30
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post #13 of 15 Old 05-10-2013, 06:07 PM
Old4X
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Quote:
Originally Posted by sloopie View Post
I've got new cap, rotor, plugs, coil and wires. Also new fuel pump and filter. Tried rejetting the Weber 32/36 but didn't help. My plug gap is right at 30

I have gotten more junk, bad out of the box parts in the last 3 years than all of the previous 40. Make absolutelu sure yod don't have a bad plug or wire (or two).

418 miles on 19 gallons of gas. Can't beat the BBD !
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post #14 of 15 Old 05-10-2013, 06:29 PM
Que89YJ
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You need to check the timing and see if your timing chain is loose. Do you hear any slap on the timing cover?
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post #15 of 15 Old 05-11-2013, 07:38 PM
NonRubicon
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Plug gap specs for the 4.2L range from 0.033 to 0.038 for the stock coil. The gap on your plugs is a bit too small.
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