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Thread: 1990 Rx-7 Backfiring and idle problems

  1. #1
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    Default 1990 Rx-7 Backfiring and idle problems

    I am looking for help with the following problems on my rotary rocket..

    1:
    Backfiring when decelerating or any loss of rpm

    When I rev the car and the rpms start to fall i hear a loud backfiring noise, I am no sure if this is the airpump or some other problem. My Rx-7 needs new exhaust as it has a leak in the downpipe, is also only has one cataltyic converter. Most of the exhaust is going to be replaced anyways.

    2:
    Fluxating rpm when idling in gear
    When I idle the car in neutral there is no problem, but when the car is in gear and the clutch pedal is depressed is goes from about 1700RPM to 1500RPM and does this continuously no matter what I do, my exhaust has a leak and I also have a preformance K&N intake but I doubt that this is a sensor problem.

    Thanks for any help in advance.

  2. #2
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    Are there any mods other than a K&N intake? The Leak in the downpipe may be allowing oxygen into the pipes which can ignite with its running a lil too rich. Have you tried checking your TPS sensor? Well anyways, sorry I wasn't all too much help BUT you can look at:

    www.rx7club.com

    and do a search. It'll probably have the answers for your problems or atleast a place you can start trouble shooting.
    1987 GX - Tein HE, s4 turbo stuff

  3. #3
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    lol...let me see here...some of this might be corrected...but...
    rotaries back fire...learn to love it...mine backfires and shoots little flames. if you are running without cats and a little to rich it can shoot big flames, and I have heard tell of a guy shooting 6 foot flames while driving down the highway(and my car apparently did that for a little while too).
    you are complaining that you are only running one cat? dude...run without any(I am assuming you car is a turbo)

    as for the rough idle...a lot of rotaries idle pretty rough, although yours seems really high...is this just at start up? could be the start up valve if so. I am lost on this one sorry, my car idles at like 500rpm so why your car idles so high I don't know.
    Originally posted by HeavyD
    you know you are making the right decision if Toma opposes it.

  4. #4
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    idle problems are usually the most difficult to solve, it could be numerous things

    as for backfiring, yeah it's pretty "normal" for rotaries to do that because the nature of the engine is to run rich
    take off all your cats and you'll be hearing more/louder backfires
    just the nature of the beast

  5. #5
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    lol...I had one one day that skipped my CD...it was awesome...
    Originally posted by HeavyD
    you know you are making the right decision if Toma opposes it.

  6. #6
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    i miss my old rx-7, that thing dumped some big flames and obnocious back fires. i loved it.

  7. #7
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    Originally posted by Go4Long
    lol...let me see here...some of this might be corrected...but...
    rotaries back fire...learn to love it...mine backfires and shoots little flames. if you are running without cats and a little to rich it can shoot big flames, and I have heard tell of a guy shooting 6 foot flames while driving down the highway(and my car apparently did that for a little while too).
    you are complaining that you are only running one cat? dude...run without any(I am assuming you car is a turbo)

    as for the rough idle...a lot of rotaries idle pretty rough, although yours seems really high...is this just at start up? could be the start up valve if so. I am lost on this one sorry, my car idles at like 500rpm so why your car idles so high I don't know.
    sorry for the thread jack , but i was wondering if there was anyway to fix the rotary from shooting flames out of the exhaust?

  8. #8
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    Originally posted by chris

    sorry for the thread jack , but i was wondering if there was anyway to fix the rotary from shooting flames out of the exhaust?
    buy an SAFC or similar piggy back fuel management system and dyno tune it so that it is not running as rich...keep in mind that rotaries should always run a little rich, but the stock maps are very very rich, which is why you shoot flames...keep it just above stoich(sp) on the a/f graph and you will be ok.
    Originally posted by HeavyD
    you know you are making the right decision if Toma opposes it.

  9. #9
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    Also a Fuel PRessure Regulator could be a cheaper way to go. But you'll stiill need dyno time to get the a/f ratio right and not damage the engine.

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