I checked around about afterburn and backfires...but my issue is a little different. At idle there is a very vaint (read not loud) 'poof' sound that comes out of the exhaust every ~3 seconds. The exhast gas also pulse with these poofs. Is this afterburn? Is this a common issue with a name? There is no smoke related with the sounds and exhaust pulses. My idle is high but steady @1.5K under electrical loads (a whole other problem) Any related threads anyone knows about. [used search but did find a similar issue) My car is a stock 93, 64K original motor.

 

all emissions intact?????

 

My car has always done what you're speaking of with and without cats. I dismissed it as afterburn but I'm not certain.

 

Does this happen only when the car is cold, only when it's warm, or both?

 

It happens when car is warm and cold. It happened in Texas as well as Boulder. I've had the car for about 3 months now and it has done it since I bought it, I thought it was a typical rotary thing, but as I learn more I'm starting to think twice.

The plugs were replaced 5K ago, but I'm about to replace them as the last change was by previous owner. I have all of my emissions equipment.

If it was afterburn wouldn't it be loud? This is a pretty mellow 'puff'

 

mine does the same thing, and i also have a high idle (1100-1200). sometimse i get normal idle, but for the most part, im at or slightly over 1000

 

it is pretty normal.

 

some times back fires can be muffled, seems pretty normal though. what kinda exhaust system do you have and what are your mods? perhaps your airpump is kicking on and off or something

 

Mine does it with a SP,DP,MP,CB. It's normal.

-BN

 

mine does that too, I was wondering about that. Its very faint.

 

If it is backfires, why don't I get any between shifts or anywhere but at idle?

-as my car stock, i have the stock exhaust system

 

I think this is even more obvious in a streetported engine.

 

mine does the exact same thing and has the same idle issues. I dont really worry about it though. Ihave a gutted precat and stock exhaust.

 

All of you guys saying you have the same problem. Do you have a higher mileage motor with stock emissions equipment? (not including cutted cats) Trying to narrow down the cause...maybe something to do with the airpump getting old? ::shot in the dark::

 

I had the exact same thing with just DP and all the rest of my emissions still intact. This was from when I first got the car with 100 miles on a new motor. Now I have the RB dual tip CB, power FC and an additional 30k miles on the motor and it still does it. I wouldnt worry about it if I were you.

 

Well, with the stock pre-cat, main cat, and catback, I never hear any of that. Once my exhaust was changed out, I could clearly hear the backfires.

Is it a possibility that the previous owner gutted the cats?

 

It could be your air pump? U should check it to see if it enage at start up and idle, only time it will stop work is when u hit 3250 rpm mark and above. Also all rotary runs rich at first when they start up. I have that problem but I notice my air pump does not click in at all times and I trace it to the wire that goes to the air pump. I play with it and I see that air pump will engage and then stop.

 

I guess anything is a possiblity when buy a used car. The guy that owned it though too real good care of it and we very intent in having it stock. Rotary Performance did all the work on it, so I doubt they gutted the cat for him. It is 100% possible that it does not have the stock pre-cat as I havent gotten that deep into the car yet. I will take a look this weekend..somethign I NEED to know anyway. I have never heard a "backfire" though at anytime since owning that car. My airpump makes a weird *** noise upon cold start though. I listened to it lately so this description will be vauge. It is a mechanical whine almost, sounds like something that isn't lubed very well but the sounds goes away as motor warms up. The sound originates from the airpump vacinity. Could it be going south?

 

It could be a leak in the exhaust somewhere. Mine does it when idleing if you slightly put your foot on the gas then lift off, and when reversing. Last time I had it serviced the guy mentioned that thegasket to the downpipe was blowing slightly as he could see a bit of carbon buildup, but nothing serious. Will get it sorted next service, gasket or maybe a new exhaust

 

I'm pretty sure that sound is overlap. Due to the location of the exhaust ports on the periphery of the rotor housing, there are times when both exhaust ports and intake ports are "open" causing exhaust gasses to be sucked into the intake. I have an 83, 89, and 93 RX7 and they all do it. It's worse on ported motors because the intake ports "open" earlier.

 

my car also has that...it has 45k miles on it with only a DP and gutted cat (no air pump).

 

Thanks for all your replies everyone!! I wasn't all that worried, unless it was abnormal. Knowing you all have it to makes me feel better haha

 

My Fd did this once at night when it was cold. It's got DP only. I thought it may be poor quallity gas but I am not so sure since I always get quality gas in my car.

It did it once and isn't a problem. If yours does it consistently, be careful as it may be something more serious related to your idle.