1980 RX-7, all original, original owner, has a serious problem with backfiring, especially when cold. Is this normal or not?
Any advice will be helpful!

Thanks

 

Checked your timing? Backfire's are pretty common in a rotary... but if you check for vacuum leaks and make sure your timing is good, you shouldn't have any serious problems with backfiring...

FS

 

Afterburn is really common on the '79-80 models because of the thermal reactor. Does it go away after it warms up? If so, you have nothing to worry about. They did that when new from the factory

If it still pops around town, there could be any number of things to check. I've found that even a small change in the idle mixture has had a great effect on reducing afterburn in my '79. Also, if there is a problem with your air control valve, the car will afterburn quite a bit.

 

It is entirely normal. Welcome to thermal reactors.

Heck even if you read the roads test from the day, they talk about the popping and banging noises on deceleration or when letting off the throttle.

 

Shoot, my 82 pops when I let off the gas... then again, there are no emissions.

 

My bridgey just started doing that...i checked the timing, all spark plugs and everything looks good. Could it be to the fact that i just decided to try 89 octane gas with some 2 stroke oil in it? That's the only thing i can think of.

 

if the engine is still completely stock then i would go get it serviced. check timing and air/fuel mixture

but like everyone else has said. its normal.
i got a fantastic flame tonight.. the side mirror went blue from the shotting flame.. havent had a good one like that in a while.

 

Ok, it's normal to a certain degree. If it has really bad backfiring you need to get ignition (timing, plugs...) checked. It ain't supposed to shoot flames, in that case you might be running too rich. If it's only during warm up, it might be the automatic choke relief system (might be different on US models then overhere though) being not very good anymore.
Some backfiring is rather normal, a lot of backfiring isn't.

 

I actually get one loud backfire - especially if I just past someone while changing gear and at high revs. I do notice its a little less once its HOT, but still get a "bang" during high speed gear change. .

 

Yes, it's pretty normal for a thermal reactor equipped car, but if the backfiring is accompanied by a sort of ringing "ping-ping" noise, the ACV is probably faulty.

 

The air fuel mixture is stupid rich. That is how thermal reactors *work*, after all. They make sure the engine runs rich all the time and then they pump a bunch of air into a glorified exhaust manifold to burn it off.

Another name for thermal reactor is "afterburner", which is a great one-word explanation of how a thermal reactor works.

 

Car is 100% original except for replacement muffler(recomended for rotary engines), and seat covers.
About how much would this service cost? Is it worth it?
Thanks for quick replies

 

You can futz with it all you like but it won't stop the popping

If you really wanted you could make sure the exhaust system is *completely* sealed up - no leaks *anywhere*. I found that the popping/banging lessened when I brazed up any small cracks in the system - was easier than replacing gaskets which would have required fighting with badly rusted bolts. But it didn't go away entirely, and it never will.

 

is your shutter valve functional?

 

This is a real RX-7... no shutter valve BS.

That's why the '79-80 intake manifold is so desirable... no shutter valve, and it is more or less symmetrical front to back.

SA's are different beasts altogether than FB's... the list of similarities is a lot shorter than the list of differences, when you get down to nuts and bolts details. They would be an entirely different generation if it weren't for the fact that the bodyshells and basic layout are sorta kinda the same.

- Pete (SA Guru)

 

i learn something everyday on this forum

 

Check: timing, vacum leaks, ignition components, exhaust leaks, AF ratio......

Good luck

 

It's a vacuum leak. The fresh air is getting inside the thermal reactor where a lot of good unused HCs are waiting for ignition. Because the thermal reactor is supposed to run hot, that's exactly what happens when you lift and the carb closes.

 

I guess it's time for me to convert a tape I have into MP3 format. Me driving my '80 around on the Last Night It Was Stock... basically lots of whirrrrrrrrRRRRR >>*BANG*<< blip >>*BANG*<< whirrrrrrrrrrr.... as I'd drive and shift and whatnot.

 

You break that technological barrier man!

 

I have converted a lotta stuff into MP3 format, it's just a PITA because I end up spending one hour recording and encoding, and four hours getting the sound balance *just right*.