Need suggestions on a backfire problem
I'm a rotary newbie, so I appreciate the help. I just bought a 79 in great shape except for a (hopefully) small problem. When I decelerate from abou 4000 RPM or more, I get a backfire. Occasionally, it will also stall at idle. The carb was rebuilt at the dealer in October of last year. New plugs and points were just installed a few days ago. Any suggestions on where to look next?
Thanks, I appreciate your help. |
Some backfiring is normal esp. after high RPM.
Ensure that the dashpot is properly adjusted, that could be the cause of the stalling problem if I read you right. Ensure that the idle speed is about 750rpm. |
I think backfire on deceleration happens with a lot of RX-7s, but especially with the early models. It's caused by residual unburnt fuel, which is inherent with the design of the RX-7 engine. Even with '84 and '85 RX-7s backfiring can happen, but it's pretty rare if all the stock equipment is working well. The only suggestions I have: when you're driving around town, try to remember to push in the clutch pedal before decelerating.. also, try to figure out which rpm gives the loudest backfire? :)
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I'm guessing that you have an exhaust leak. That's what caused my "80 to backfire. If you have the stock exhaust, with the thermal reactor, the headpipe may have a hole in it underneath the heat shielding.
Those pipes cost over $1100, so if it has a hole you may need to have it welded. I did that before I got my Racing Beat header. |
You might also want to check the butterfly valve in the intake manifold. Sometimes it gets stuck and causes the engine to backfire. You may also have a vacuum leak in the hose that runs into this mechanism.
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'79 doesn't have the shutter valve. Neither does '80. That's why the '79-80 manifold is sooo much better than the '81-85 part.
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