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Cool backfire when accelerate!

Car is 996tt. If I want to accelerate while the car is cruising at a low speed (around 20 to 30 mph), I'll hear a knocking sound at the back of the car with a little hesitation. My mechanic said it may be a backfire. What do you think?

Old 07-03-2005, 07:18 PM
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Maybe you have injected too much fuel into your engine. Buy a exhaust gas temperature (thermocupule) gauge, This will tell you the air/fuel combination of the engine. The adecuate exhaust temperatures is 1,400 or 14:1 air fuel ratio. A number below that, like 13.1 means that the mixtures is too rich. Temperatures over 1,400 degrees or more than 14.1 means that the mixture is lean. Lean condition elevates exhaust temperatures. Rich condition lower exhaust temperatures.
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1972 911T
1991 Mazda RX-7 Turbo II
Are you car loosing power? When was last time you service your fuel injectors? Dirty fuel injectors? Why no try a complete fuel injector cleaning service and return the dignity to you car. Visit www.rennsportfuel.com and we will return your injectors back to life!
Old 07-03-2005, 07:42 PM
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Actually, it is more like a "thump" at the back (with a slight hesitation) when accelerate from cruising speed?
Old 07-04-2005, 01:56 AM
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That sounds to air/fuel mixture problems.
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1972 911T
1991 Mazda RX-7 Turbo II
Are you car loosing power? When was last time you service your fuel injectors? Dirty fuel injectors? Why no try a complete fuel injector cleaning service and return the dignity to you car. Visit www.rennsportfuel.com and we will return your injectors back to life!
Old 07-04-2005, 06:20 AM
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Dealer just changed the MAF sensor and a few diverter valves because of a slight vacuum leak.

The mechanic is unable to find the cause of the rear end clunk sound when accelerate quickly during low speed cruising (it doesn't clunk all the time when accelerate). Mechanic said everything (mounts, suspension and sway bar) is tight and he is still checking to see if there is anything else which could cause the clunk.

I've seen some web saying that the noise could be from a faulty transfer box or torque converter, any views?
Old 07-04-2005, 08:04 PM
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What about the c.v. joints?
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1972 911T
1991 Mazda RX-7 Turbo II
Are you car loosing power? When was last time you service your fuel injectors? Dirty fuel injectors? Why no try a complete fuel injector cleaning service and return the dignity to you car. Visit www.rennsportfuel.com and we will return your injectors back to life!
Old 07-04-2005, 08:20 PM
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they said they are ok too.
Old 07-04-2005, 08:25 PM
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Mechanic said the subframe and sway bar are tight. Also, the engine and transmission mounts are ok.
Old 07-05-2005, 05:38 PM
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Mech said to me today that the car has a slight backfire when accelerating from a low speed. He has not yet been able to locate the cause of the backfire. Any views?
Old 07-07-2005, 06:17 PM
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Consdier fuel injectors if you have them being clogged, or a clogged fuel filter, same thing happens to me when i ran her down to nothing and some scale came through the lines.

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Old 07-31-2005, 02:51 PM
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