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deceleration backfire and engine studdering

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Old 10-18-2007, 08:27 AM   #1
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deceleration backfire and engine studdering

searched but couldnt find the exact situation.
acceleration is no problem. nice and smooth with plenty of power. when the RPMs level off and hold steady, I get a studder or miss with some light backfiring. the studdering and backfiring gets worse when decelerating in gear. 22re w56. has a thorley header with i believe 2 1/2 inch exhaust. the exhaust is new but there could be a small leak at the manifold. I doubt that would cause it though. any thoughts. thanks
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Old 10-18-2007, 08:38 PM   #2
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Look this over for the related symptoms.
http://personal.utulsa.edu/~nathan-b.../3troubles.pdf
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Old 10-18-2007, 09:20 PM   #3
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i have that same problem, but i wouldn't call it a problem. i get that same backfiring with my new exhaust when I'm in gear. i think it sounds cool. i dont really think theres any performance problems that come along with it. i have a modified intake too and that could also be one of the reasons for my "backfiring." is there anything else i'm missing?
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Old 10-18-2007, 10:10 PM   #4
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Yeah, you're air/fuel ratio is off or maybe an exhaust leak. Depending on if it's the exhaust or the intake depends on how serious it is. Either way, valve damage can happen. You ought to fix that.....even though it sounds cool.
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Old 10-18-2007, 11:02 PM   #5
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maybe a dirty AFM?
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Old 10-18-2007, 11:15 PM   #6
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Did the problem first appear when you put on your new header. If so, I would also suspect you have an exhaust leak. If air is entering the exhaust system it can fool your O2 sensor into thinking your running lean. Then it adds more fuel than your engine can cleanly burn. The left over fuel from the combustion mixes with the air from your air leak and you have combustion in your exhaust system. Make sense???
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Old 10-18-2007, 11:30 PM   #7
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What sort of sparkplugs are you using?

I have a similar problem, running the 22re with an LC header, new cat and Flowmaster 50 through new 2.25" tubes. It only happens at idle. I definitely had an exhaust leak before the new system was installed, because the stock header had split at the weld where the individual cylinders pipes come into the common header. Anyway, when I got the new system on, my problem didn't diminish. But, when I was getting my new tires put on, I had the shop do a compression check. While doing that, the owner suggested that my plugs might be the issue, as I had Bosch plugs in at the time. He said he'd go ahead and swap them out for some NGK's (which I have always used in the past) since he already had the wires off doing the compression check. The NGK plugs reduced the problem by a couple orders of magnitude, but did not completely eliminate it.

Any other possibilities besides an air leak? I have considered a bad O2 sensor, but those are usually accompanied by a check engine light. The other thing I've considered is that the injectors might need cleaning. Could that be a cause? If it is a bad air/fuel ratio, what would be a way to pinpoint that, or would you only be able to know by cleaning the AFM and seeing if it helped?
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Old 10-19-2007, 09:02 AM   #8
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Quote:
Originally Posted by thook View Post
Yeah, you're air/fuel ratio is off or maybe an exhaust leak. Depending on if it's the exhaust or the intake depends on how serious it is. Either way, valve damage can happen. You ought to fix that.....even though it sounds cool.
Leak at exhaust manifold could definately have something to do with problem as well as a possible total lack of backpressure
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Old 10-19-2007, 12:58 PM   #9
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Timing?
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Old 10-19-2007, 01:17 PM   #10
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When I bought the truck, the header was already on and there was flow master with oversized pipes and no cat. loud as hell but it ran just fine when I got it. I put a better exhaust back on it with a proper muffler with more backpressure. this problem didnt start till a few months after I put on the new exhaust. That is why I dont think its a back pressure issue. As for the timing, the PO claimed he replaced the chain and put new steel guides. Those guides are leaking a bit so maybe the timing job was botched. If it were timing, wouldnt I notice it when accelerating. like a missfire or something? I think I will start with the simple things like a new manifold gasket and plugs, cleaning sensor connections and whatnot. Then move to more complicated things like the timing. The backfiring doesnt bother me as much as the noticeable engine studder/missfire. ALmost like it wants to stall or something.
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Old 10-19-2007, 01:30 PM   #11
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Timing?
Valve Lash also ?
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1994, 22r, 22re, 43l, accelerating, backfire, backfires, backfiring, decelerating, deceleration, engine, gmc, intake, jimmy, studders

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