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Registered
Join Date: Jul 2007
Location: Indiana
Posts: 1
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,73 911 w/mfi backfires when slowing down
My 1973 911T w/mfi backfires ( with a very loud and annoying ka-bang) when the car is slowing down. This occurs when coasting and slowing in 4th or 5th gear and in a fairly short distance ( hundred yards or so). This problem was going on before and went away when I replaced the timing belt a couple of years ago. Now, 10,000 miles later the backfiring is back again.
Problem cause and remedy suggestions? By the way, if it were easy to replace the timing belt, I'd have already tried that... Hoping someone has a cure. |
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07-01-2007, 07:35 PM
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Registered
Join Date: Feb 2005
Location: SF Bay Area
Posts: 152
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There is a circuit to stop backfiring when coasting. It consists of the switch on the left stack, the rpm speed relay and the solenoid on the MFI pump. The way to test is to rev the engine to 2000 rpm (in neutral) and while holding it there, depress the switch on the left stack. The rpm should drop to 1300 rpm then rise to 1500 rpm and continue cycling between the two. When you let go of the throttle, it should drop to idle. At idle, the switch on the left stack should be depressed by the lscrew at the end of the lever arm. All this is described in CMA. Is all this working properly? Gary
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07-02-2007, 06:54 AM
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