ok, here's the deal. I recently purchaced an 84 gsl. I know nothing about rotarys, and i have a problem. Since i bought my car it has always sputtered and backfired during deceleration. My exhaust is straight-piped from the manifold, into a high flow muffler. No cats or resonators. Today i noticed a tooting sound coming from my air cleaner. There seems to be a possible link between the two. When i plugged the vacuum hole in the air cleaner, the car didn't seem to backfire as much. However, it did take longer for the RPM to come down after reving the engine. I really want to stop the car from backfiring!! It's really embarasing to be driving such a great car that sounds like a poorly tuned Ford Pinto. If anyone knows how to help me with this problem, it would be greatly appricated. thanks!

 

welcome to the rotary world my friend,
the backfiring is like a rx7 signature,
i grin when mine backfires cause i know im trailing flames out the rear,
theres alot of hp hidden in that engine of yours,
i suggest looking around here on the forums for some usefull info to put that rotary to work,

the thing you were reffering to is called anti afterburn or some **** like that,
its all in the chiltons manual,
i suggest picking one up,
and grab a haynes ,there more specific but leaves out somethings that the chiltons has,
keep it in the bathroom at the least and use it for reading material.

also click my sig and check my tech section,
it needs some updating i know,

most links in my tech section have more to them,
you just have to poke around a little,

also search the forum for dlidfis
and atf treatment

if need more lmk

 

hey V8Kilr
another question for ya
this "anti-afterbuen" can this be cured by running a hotter plug, better aftermarket coils ( I.E. Accel super coils) and better plug wires?
~vince~

 

The only way to "cure" it is to sell the RX-7 and get something else. All rotaries will pop and spit out the exhaust to some degree, it's one of their characteristics.

 

if that's the case, ( selling it ), i will deal with the backfiring! I'm not willing to part with my baby!
i love her too much!
~thanks for the input~

~vince~

 

In my opinion, if you have a stock port motor, stock carb and manifold, you should not be backfiring. I think something in your emissions control system is functioning incorrectly.

My RX-7 (stock Nikki, full RB exhaust) used to backfire and spit flames until I removed the emissions junk. Now it *never* backfires, ever. This is the same with other nicely tuned stockport FB's I've seen.

I think the backfiring has a lot to do with the shutter valve system operating incorrectly, mine was definitely fucked up in some way. Backfiring might be cool, but it's unnecessary with a stock motor and definitely no good for exhaust components.

 

even with my exhaust, the seven still backfires.. just does not sound the same as before with the stock exhaust.

all sevens, all generations, do it.. just part of the fun.

i have only shot flames out of my car once.. kinda dissapointed about that.. i need to figure out how to do it on demand

 

Again, relatively stock RX-7's should not backfire. Get rid of that malfunctioning emissions control garbage and watch your backfires disappear.

 

the high rpms when you let off the gas may be from the dash pot settings,http://pittdp.homestead.com/underhood.html

 

Is this the vacuum hose that you plugged? You say it got better, and that hose is making a noise. (Like a rabid goose being sucked through a shop vac in a tornado?)



If so, just plug it up permanantly... It should not be sucking at idle, only on decelarion to about 1000 RPM.

It's the shutter valve. It causes rough idle, backfiring, and noises as you describe when it fails. You must remove the carb and some of the intake to get to the actual valve for removal and/or replacement.

Many of us just plug it up. Results are some small backfiring, slight change in fuel economy, slight change in acceleration/deceleration of the engine.

 

Pele,
Thank you, for taking the time to take a pic and post it. That really helped me understand what was wrong with my car. I haven't tried permanantly pluging the hole yet (gonna do it first thing in the morning). Tomorow i will try your suggestion. I will write you back,and let you know how it went.
thanks again!


~Vince~

P.S. Would it be a good idea to replace the shutter valve, or, just plug it up? And, the change in fuel economy and acceleration/deceleration?? better or worse?

 

not true
here is what you will need,

about 6 cats, maybe 7
a big thick restrictive air filter,
very very hot plugs,
direct fires ,full blown msd

am i forgetting anything?

but yes in the real world the best thing would be to sell it,

i really hate to steer someone from an rx7,but thats the first complaint i heard the it "really" bothered someone,

it may get anoying but if you really cant deal with it then i dont think a rex is for you my friend,

come to a rx7 meet,
you'll fit right in

 

btw the more i modded my 7 the more noise it made,
now it gives out a puff in between gears if i take to long to shift,
its not a pop,
just and nice mellow poof

now on the other hand if im in lets say third gear and take it up to 5,000 rpm then leave it in gear and let off the gas,
well
grrrrrrrr,pop,pop,pop,pop,pop,pop,grrrrr,poof,pop, grrr

 

Things to check:
Deceleration valve
ACV valve
Holes (even little ones) in your exhaust
Timing
Distributor cap and rotor
Plug wires
A stock well running RX will not backfire. In fact my 80 with the RB exhaust does not backfire either. Do not listen to people who say it's normal, it's not.
of course that's just my opinion, I could be wrong,
hanman

 

i think that it is normal for all rx-7's of all generations.. every seven that i have seen or heard of back fires..

now , it was definatly less noticable when i got my new exhaust, but it is still there.. sounds more like back pressure now.

 

Exactly

 

My 85 never did it, I removed the ACV , air pump, all the emission stuff, and straight pipe from maifold all the way back to the factory muffler and mine was OK

No my 80 was a different story.... I just went to a set of headers on it, and no more problem...

 

My RX-7 had some small backfiring, very quiet, not very often... Here's what was wrong with it:

Bad shutter valve, plugged that pipe up.
Rich mixture
Precats fallen apart, rattling inside
High performance Midas catback exhaust
High milage
Lead foot on the pedal
Umm. I think that's about it.

Backfiring and sputtering and popping is NOT normal, but can be expected as many of us do not maintain the emissions systems or remove them.

 

I plugged the shutter valve this morning with good ole' duct tape (the handyman's tool for fixing everything).

It worked great!! Not near as much backfiring, smoother idle, (idle now at about 950RPM) a little bit higher than before, but, at least it idles better.

But the biggest improvement is the deceleration!! Huge difference!! Not near as much backfiring. And when it does, it's quiet little poofs, instead of loud BANGS.
Thanks again Pele!
You saved me alot of time and money.

~Vince~