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  #1  
Old May 13th, 2008, 06:55 PM
Andrew Vick
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Andrew Vick
95 D90
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Backfire

I did a search and nothing caught my eye.

I live in the mountains, and commonly use 2nd and 3rd to control my speed coming down grades. I'm getting an occasional backfire, which to me means unburned fuel, so probably running rich. Any suggestions?
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  #2  
Old May 13th, 2008, 09:30 PM
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Davis
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Chris Davis
94 NAS D90 6.2LS
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Sounds like one of your cylinders is not firing and the cat is exploding the fuel. You can try and use an infrared thermometer and check the exhaust manifold to see if there is any temp difference--that would be the bad cylinder (either compression or spark). If it is only very occasionally, it is much harder and an inspection of the plugs may tell you--it will probably be more subtle or you won't be able to tell at all.

If there are no indication, start with a compression test. If they are all in range, you may have a bad plug wire , fuel injector, or even an alternator that has a zenier diode going bad that bleeds A/C into the system and can cause misfiring fuel injectors.

Maybe this helped, maybe no. No easy answer from me, plus I am really tired and have been drinking and it is only 7:30 on tuesday.

Good luck!
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  #3  
Old May 13th, 2008, 09:55 PM
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Dave Lucas
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Have you modified the exhaust system? Lack of backpressure can cause a poping / backfire type of noise on deceleration.
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  #4  
Old May 14th, 2008, 07:49 AM
Andrew Vick
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Andrew Vick
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Thanks for the input! I'll pull the plugs and see if that leads to anything. Dave: the exhaust is aftermarket that was put on previous to my ownership. Given it's sound, I would bet you're right.

Any other thoughts?
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  #5  
Old May 14th, 2008, 05:59 PM
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Gren_T
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Gren Thomas
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Hi Andrew, i would also go for an exhaust problem most likely a leak in the joints or on the manifold, i used to have the same thing happen on my v890 after a hard time off road.
A quick trip around with a 13mm spanner and it would stop.

could also be a leak in the air intake maybe a split or crack in the air inlet hose or leak in the inlet manifold.

have fun

Gren
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  #6  
Old May 16th, 2008, 08:38 AM
Andrew Vick
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I'll try that this weekend. Thanks for the suggestions.
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