Hi all, I have an 84 RX-7 GSL-SE. If I rev the engine up and let off the gas, it will often make a few backfire sounds (not gunshot loud, more like BB gun sounds) at around 3K rpm. Could this be exhaust-related, injector-related, or spark plug-related? Thanks

 

did you modify the exhaust?

 

No, everything is factory stock on the car, except for a fuel bleed-off valve that the previous owner installed Fuel Injection Pressure Bleed- Off Kit

 

reading Mazdatrix's website they state...
Your fuel injectors might be leaking and putting excess fuel into the motor which is popping in the exhaust on decel.

 

Right, I was thinking about that being a possibility, but wanted to get some opinions and experienced theories before making the purchase of new injectors.

 

regardless, it also may be worth your while to give the exhaust a good once-over. the extra fuel in the exhaust still needs air to explode/burn, just like in the intake and the thing with those exhaust backfires is they can and WILL blow out pieces of gaskets, creating more air leaks and thus more backfires.

 

Sorry to seal post but this comment made me abit worried.

Mine back fires hugely as in gun shots all thru the rev range untill I give it gas or clutch in.

Would it be worth changing the injectors to see if this fixes the problem and going from there as far as the gasket? Also is the exhaust gasket the same type of deal as a piston exhaust gasket? A somewhat easy fix? Or more like a rota seal, quite costly and not something is want to try on my own (have done level 4) automotive and have a decent idea of what I'm doing.

It is also heavenly over fueling I have been told and will get it retuned. This could be adding to the back firing I'm guessing too?

Thanks

 

exhaust gaskets are exhaust gaskets whether reciprocating or rotary. they should be at every joint in the exhaust system. they may be a pain to get at because of rusted bolts and such, but nothing complicated.

i'm not familiar with your car/setup, but based on this ^ i need to ask if you're running some kind of aftermarket EMS. are you?

 

Ems as in engine management system?

I have a plug in link g4 and a after market exhaust

And have had a power run done where I was told it was over fueling and another company look at the set of the timings on the link when I got the car checked out and he was saying the timing was off quite abit to where he would tune it

 

well, unfortunately, your needs may have overrun the scope of this thread because you actually have tuning issues. the OP, with a stock GSL-SE, does not.

i'm not familiar with the system you have. in fact, i can't say if i've ever even heard of it. at any rate, you may have to start a thread seeking help if your tuner is unable to solve your issues.

 

That's ok I was Morley just wanting to find out a bad tune could also cause this problem.

I don't need tuning help ATM as my tuner has it all sorted but I wasn't awear the back firing can be a big problem with the exhaust gaskets so didn't bring it up with him.


Thanks for the help

 

Holy thread jack Batman!

I have an 85 gslse. Mine seems to have a stumble in the low rpms, with an occasional muffled pop on decel. It passed smog fine, but I'm searching to solve the same symptoms.

New fuel filter, plugs, wires, cap/rotor, cleaned terminals and used dielectric grease in some major spots.

 

Thanks for the reply all. My next step is to replace the spark plugs with new NGKs and then remove the injectors to be sent in for servicing. While that's out I'll be checking the exhaust system for leaks. Wish me luck!

 

Also make sure the ACV works.

Test procedure is in the FSM. There's an anti-afterburn valve within that whole assembly on the lower intake.