Spotty hesitation and idle - JeepForum.com

 
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post #1 of 3 Old 08-15-2006, 06:47 PM Thread Starter
sentinal02
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1992 YJ Wrangler 
 
Join Date: Feb 2003
Location: New York
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Spotty hesitation and idle

Hey guys, looking for some opinions on this one.
The past two days the jeep has started hesitating in all gears when i try and accelerate. it doesn't happen every time though. ran fine to the store last night, come back out and it would hesitate. go for a little while and it would go away. this all happened out of the blue with no gradual loss of power or any other indication that anything was wrong. also it tends to idle erratically when it happens, ie drops to 400 rpms climbs to 800 drops again, and keeps on cycling like that. this morning i started it, it went to stall so i blipped the throttle and it backfired, sounded like it was on the exhaust side. since then it hasn't done the hard hesitation i was getting but i THINK it's still a little sluggish. could be that i'm just paranoid though. this is all before i've done any work to it. since this morning i've done a full tune up except for the O2 sensor. the rest (plugs, wires, cap, rotor, air and fuel filters) were changed. I don't notice any difference but like i said it wasn't acting up after that backfire this morning and i put close to 30 miles on it between that start and doing the tune up. the exhaust is new (maybe 3000 miles) from the manifold back. the O2 is about 30K miles old. from here i'm thinking one of these 4:

O2
Fuel pump
Coil
TPS

the plugs looked perfect when i pulled them so i'm kind of ruling out the coil. they were however gapped between .055 and .067 which is almost double the .035 spec. it was fairly even on all four plugs however and the burn pattern is a nice even coat of tan. seems to me that while they were due for a change they didn't seem to be the cause of the problem, or indicate that i'm fouling out or running lean. any thoughts guys?


RIP: '88 YJ 2.5L Ax-5 NP231
Posi-Loked. Herculined. Optima yellow top. 1" Shackle, 2" BDS. Cragar 397's Aussie front.

92 YJ 4.0L Ax-15 231
5" springs, 1" shackle 31's or 35's depending on my mood
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post #2 of 3 Old 08-16-2006, 10:43 AM
King03Kev
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Is it possible you just got a bad tank of gas, maybe a little water in the gas that after backfire cleaned out the injectors. Just guessing because it sounds like you checked just about everything else.

kevyj87 '87 I6 5spd, 215,000+ miles, Herced, Nuttered, Weber, HEI, RE 4", 1" BL, 4:11's, np231, 33x12.5's, SYE & shaft, 1" brown dog mm, home made bumpers front & rear, Ramsey 8,000lb winch
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post #3 of 3 Old 08-16-2006, 03:51 PM Thread Starter
sentinal02
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1992 YJ Wrangler 
 
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Quote:
Originally Posted by King03Kev
Is it possible you just got a bad tank of gas, maybe a little water in the gas that after backfire cleaned out the injectors. Just guessing because it sounds like you checked just about everything else.
yeah, was thinking that myself as well. mainly because this tank was from a station that i don't usually fill up at being i was on a long trip. i dumped in some STP fuel system cleaner with the new tank of gas yesterday so we'll see. right now the hesitation seems to be gone, but it's idling a bit higher than normal and when i first start it up in the morning it idle rough until the engine starts warming up. gonna check for vac leaks tomorrow.

RIP: '88 YJ 2.5L Ax-5 NP231
Posi-Loked. Herculined. Optima yellow top. 1" Shackle, 2" BDS. Cragar 397's Aussie front.

92 YJ 4.0L Ax-15 231
5" springs, 1" shackle 31's or 35's depending on my mood
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