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Unread 10-22-2013, 09:46 PM   #1
trailnYJ
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Join Date: Jul 2012
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Cuts out then backfires!?!

I have been havering this problem to were I'll loose rpms even if I haven't changed how much I am on the gas pedal. It then kinda sputters then back fires. Now this doesn't really happen unless I'm on a 1/4 tank of gas or if I've been driving 1/2-2 hours on the freeway. It popped up a code for the AIS circuit? I was wondering if I can replace that or any other ideas on why this is happening!

95 YJ 2.5 4 banger with 4"rancho lift on top of 33x12.5/15

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Unread 10-23-2013, 05:23 AM   #2
Que89YJ
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1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
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The AIS has nothing to do with timing and if you are "backfiring" then I doubt the AIS is the culprit. The gas is interesting. If it truely is gas related then you are going to need to put a pressure guage on the fuel rail and drive it until it happens. By the symptoms I would have thought you have a cat problem. If it is anything electrical it would be more consistent so I am thinking fuel or exhaust.
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Unread 10-23-2013, 08:15 PM   #3
trailnYJ
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Well It had done it more before I had replaced the exhaust manifold gasket, now it only really does it when I am at 1/4 tank and it's warm. Why would it show a code for the AIS? It had popped on right after a backfire :/

95 YJ 2.5 4 banger with 4"rancho lift on top of 33x12.5/15
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Unread 10-23-2013, 08:17 PM   #4
Que89YJ
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1989 YJ Wrangler 
 
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Do the pressure guage. It is easy enough to check
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Unread 10-24-2013, 05:03 AM   #5
vadslram
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1990 YJ Wrangler 
 
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I would bet more on an ignition problem. When it cuts out there is still fuel and air going into and out of the cylinders. Once the plugs fire again you have a bunch of combustable mixture in the exhaust system and it will ignite.
Not that I ever did that on purpose by turning the key off in gear then turning it back on to freek pedestrians out
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Unread 10-24-2013, 05:58 AM   #6
Que89YJ
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1989 YJ Wrangler 
 
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Location: Detroit, Michigan
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TrailnYJ Please fill out your profile. I see the info at the bottom of the first post but it is a pet peave with a lot of people here.

The backfire word gets thrown out on the forum real quick and it drives me nuts because it immeadiately means there is a timing issue. The backfiring should mean you have the cylinder firing through the throttlebody and the exhaust if it is real backfiring.

Vadslram
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You are one of those guys! LOL
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Unread 10-24-2013, 12:14 PM   #7
vadslram
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Quote:
Originally Posted by Que89YJ View Post
TrailnYJ Please fill out your profile. I see the info at the bottom of the first post but it is a pet peave with a lot of people here.

The backfire word gets thrown out on the forum real quick and it drives me nuts because it immeadiately means there is a timing issue. The backfiring should mean you have the cylinder firing through the throttlebody and the exhaust if it is real backfiring.

Vadslram
BTW:
You are one of those guys! LOL
I am one of something at least

Backfiring isn't ALWAYS timing. It is definitely timing if it is a constant backfire, Either from the intake or exhaust and it could be spark timing or valve timing.
If it is intermittent and accompanied by a sudden loss then return of power and the backfire comes from the tail pipe then it is most probably in the primary ignition circuit. Maybe call that external combustion since it is technically going through the system in the right direction?

It COULD also be a symtom of bad valves if it is coming out of the intake.
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Unread 10-24-2013, 01:05 PM   #8
Que89YJ
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1989 YJ Wrangler 
 
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I agree with the backfiring too. My only problem is the word is thrown around too easy and it isnt what they meant if you know what I mean. Loading up with fuel like...somepeople around here do on purpose....give you a what could be misinterpited as backfiring. If you have a timing issue it is usually constant not intermittant. The air intake temp sensor is interesting. It will cause a flat response in the pedal so it needs to be fixed asap but it doesnt explain all the symptoms. I am betting there is a bad O2 or coolant temp as well. PM me when you get back to this one. I like an interseting issue to troubleshoot.
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