My car has backfired when I shifted high and fast since i got it. A week ago I removed the cats and bolted up a cheap temporary muffler(till i got the money for my RB setup). The car still backfired but it was louder.
I just disconnected the airpump a hour ago.( i didn't remove it, I just pulled off the hose and plugged it, along with the cat air tube.
Heres what happens now.
Idles lower(like 400 rpms or lower, seriously)
Doesn't backfire (no matter how hard and fast)
The thing backfireslike three or four times(hard) on off throtle over 4000

What can I do to help stop this.
82 gs stock carb
My exhaust is a stock manifold, no cats, cheap thrush boss turbo muffler. exits about 6 inches before the back of the door.

I was thinking ATF treatment. (never been done to car and 90,000 miles)
adding more pipe so it exits near the axle.
Reset timing (no timing light, crank pulley timing mark not aligned, and not familiar with timing a rotary so I am dont really want to do this)

Please help!!

 

To rid yourself of the deceleration backfire, simply redesign the rotary engine.

Mine does it too, all three motors I've had in the car have done it, two different intakes, at least four different exhaust setups, and three different ignitions. I don't mind it since it only happens when I drive hard.

Just yesterday I was told that I shot a 4 foot white flame out my muffler (thrush turbo - offset in/out).

 

IF it continues I suppose it wont be so bad when I have the exhaust actualy coming out the back. flames should be cool. It just sounds so "beater" the way it is now.

 

These are pretty big backfires though.
Not, pop-pop

More like ka-bam ka-pop pop.
loud as hell

 

With disconnected air pump , did you remove the ACV and cap the opening? My 85 NEVER backfired... My 80 was bad about it, untill the RB headers and no ACV..

 

Those are the ones I get - they sound like a shotgun from in my car. Except mine only does it when you're off the throttle in at least 7k and come down to 4.5k or lower semi-fast (braking).

 

I didn't remove the air control valve, I just pluged the air pump hose (at air pump end). and I pluged the cat injection hose. (with a wine bottle cork, worked great)
I can shift hard and fast at redline and no backfire. it backfires on off throtle. a couple of loud pops.

 

why block the air pump hose, it's just tryin' to pump air....

 

yeah, but if you don't plug it, it makes all kinds of weird noises under the hood while you're driving.... hey, come to think of it, wouldn't it sound like a turbo at high revvs? *Ricy ricy ricy**

Jeff

 

You wouldnt believe what my backfires sound like.... (Well, you probably can, and have had the same prob )

Well, if i wind mine above 3 grand..... and then let off, or shift, well..... it sounds like a 12 gauge shotgun plyin under my car I hate attracting attention to the nieghbors.......LOL....... I hate attracting attention, PERIOD. So...... my timing is set right..... my carb air/fuel screw, is 2 and 1/2 out, then I adjusted the idle screw.... What else? Exaust, acv? Those are next....



LATERZ, Andrew

 

Your ACV is to blame. As long as even a few molecules of air can get to your super-heated exhaust coming from the exhaust ports, you're going to back fire. I'm running a RP header into a 3-way cat. Before the change, I had to deal with the back-fire, also. I'm still unconsciously playing the gas pedal when I shift because that was how I got it to stop popping when I was driving at speed. That was before I found this forum and the dashpot on the accelerator brackets. After the change, I have not had even a hint of any backfiring...

 

dash pot brackets? What?

 

It looks like a vacuum canister sitting near your accelerator cable bracket. When it's working right, it won't allow the butterflies of your carb to snap shut if you lift off the gas suddenly...it's a black plastic thingamajob!

 

The air pump is venting into the air. The hose for the airpump from the acv is plugged, not the pump itself.

 

It's the ACV valve itself causing the problem, it doesn't matter that the opening is covered on it....