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Join Date: Aug 2005
Posts: 34
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backfiring during deceleration
I just put 83 motor back in car after repairing broken head studs and went for test drive. During downshifting or rapid decline in RPM's engine rapidly backfires. This does not occur during acceleration only during downshifting and not at idle.
Any suggestions or ideas would be appreciated. Thanks Mike 1974 911S |
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02-08-2006, 10:12 AM
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Lean mixture? Air leaks in the intake?
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John '69 911E "It's a poor craftsman who blames their tools" -- Unknown "Any suspension -- no matter how poorly designed -- can be made to work reasonably well if you just stop it from moving." -- Colin Chapman |
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02-08-2006, 11:28 AM
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Timing? Vac leak, mixture.
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02-08-2006, 11:53 AM
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Posts: 34
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mixture check
On the CIS systems how do you check the mixture or change the mixture.
Thanks |
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02-08-2006, 11:56 AM
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CIS needs a few special tools, Wayne has 'em.
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02-08-2006, 11:59 AM
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Join Date: Jan 2004
Location: CT
Posts: 11,549
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My experience is that this condition is caused by a leak in the exhaust (hole in muffler or leak in the heat exchange to muffler connections). Lifting off the throttle rapidly causes a rich mixture leading to unburnt fuel in the exhaust stream that gets ignited when exposed to outside air at the exhaust system leak.
Check you muffler connections for carbon trails.
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Tom Butler 1973 RSR Clone 1970 911E 914-6 GT Recreation in Process |
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02-08-2006, 06:16 PM
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Air Medal or two
Join Date: Jul 2003
Location: cross roads
Posts: 14,079
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more then likely lean mixture...not necessarily a bad thing on deceleration......just too lean to fire in the c chamber....backing off is an other way to put it
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D troop 3/5 Air Cav,( Bastard CAV) and 162 Assult Helicopter Co- (Vultures) South of Saigon, U Minh Forest, Delta, and all parts in between |
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02-09-2006, 09:03 PM
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1969 Porsche 911E 2.0 E
