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Join Date: May 2005
Posts: 95
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Backfire!
Does anyone know how to fix a backfire problem which happens on deceleration (car is 996tt)?
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06-21-2005, 06:24 PM
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Location: US
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Remap your fuel injection. But backfires on decel are nothing out of the ordinary.
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06-21-2005, 06:40 PM
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I think there may be unburnt fuel getting into the exhaust that cause a "pop" sound. Will cleaning the injectors help?
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06-21-2005, 07:31 PM
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Exhaust leak? Check at idle for pressure escaping around your flanges. Mine and a friends were both doing this. Flanges were leaking due to warp from age and improper seal. Sealed them up, problem fixed.
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Jim Dean LL.B. - London, Ont, Canada. 1969 911T "Blood Orange" Euro (Brought over from Germany in 86) Engine and brake system rebuilds 2006 & 2007 "Oversteer scares passengers, understeer scares drivers." |
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06-21-2005, 08:35 PM
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Location: south western ct
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definately check for exhaust leaks before remapping fuel. finding a crack or weak spot in your exhaust (while it is no fun) is certianly better than concealing the problem by leaning the mix. plus in a turbo car you would then have to worry about preignition (which would be much worse than the occasional pop). sorry if i am stating the obvious but as a person who grew up with rx7's though, backfiring on engine breaking is something that i have become familiar with.
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06-22-2005, 12:04 PM
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Do you guys think a dirty fuel injector or spark plug may cause this popping (causing unburnt fuel to flow into the exhast)?
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06-22-2005, 08:12 PM
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Mechanic said there was a leak in the exhaust. However, after fixing the exhaust leak, there is still a little bit of popping when decelerate. Do you guys think that this may be caused by a bad "air injection diverter valve"? What exactly is an "air injection diverter valve"?
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06-24-2005, 05:37 PM
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procedure i would go throught after squaring all exhaust leaks:
pull your plugs to see if everything is consistant between cylinders. if that checks out (i'm not sure if a 996 has a boost/ vacuum guage) check to see if manifold vacuum is normal on engine brake. double check ignition timing. clean your plugs and generally test/tune up all ignition components (can't ever hurt). replace diverter valve/remove emissions if not in ca. or even if you are and are willing to do the work every other year. shorten injector pulse. learn to live with slight backfiring on sharp lift off. god knows i have.
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06-24-2005, 06:20 PM
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what is an air injection valve? part of your smog eqpt.. a preasure differential opperated switching diaphragm that deals with supplying o2 to either your cat or to atmosphere vbased on engine opperation as a catylist to burn off remaining hco's with o2 from your intake or to vent to atmosphere to avoid backfiring on decel.
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06-24-2005, 06:25 PM
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so yeah it could and likely is that but why not look into the easy stuff first?
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06-24-2005, 06:27 PM
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1969 Porsche 911T
