My 7 seems to backfire alot on deceleration is this normal as nobody in the real world seems to know.

The exhaust has been replaced with a jan speed and the air blower etc has been removed .

If it aint normal what can i do to fix it.

Stu

 

From my limited experience with rx7s I would say it is normal. All of the mostly stock ones with air pump removed run quite rich, which are the ingredients for backfiring.

 

Thats ok then, I was getting worried as it is really loud sometimes (great fun for me watching people diving for cover)

Will it damage the exhaust.

 

From what I read here with all the cats removed its normal. I had a custom Y pipe done that removed the main cat and it would backfire everytime I'd redline at WOT and let off/shift. Now after having gutted my precat (busted honeycomb) it backfires noticeably louder.

 

Depends on what exhaust you have.

 

I have a header and a cat and it still backfires like crazy all the time. My car is running stupid rich apparently.

 

Actually, it's not unless you're hitting redline every 10 seconds!
Try and adjust the TPS...


-Ted

 

My narrow range tps is broken, so i have it unplugged right now. That could be why I'm constantly back firing.

 

omg i have cats and i still backfire going to all gears. does that mean im running super rich??

 

If you don't have cats, that's not uncommon. I have the same thing happen, but only on deceleration in the higher RPMs (i.e. not below 5k). Oh, and I'm n/a.

Stupidkid- I believe that does mean you're running crazy rich.

 

One of the REAL roles of the TPS is what RETed mentioned above. When you let off the throttle, the injectors shut off, or are supposed to shut off. On a properly set tps they will. If the fuel does not shut off when you let off the pedal, then excess fuel goes into the rotor chamber and explodes in the exaust.

Also, the ACV has a anti afterburn valve built into it. That puts airpump air into the INTAKE during rapid deceleration to lean the mixture out that is going into the exaust. That's the only time a ACV should put air in the intake.

 

How do you go about adjusting a TPS? Is that the little "****" on top of the engine that changes the lean/rich?

 

The tps adjustment is a screw near the tps sensors. It is on the cam that moves the throttle position sensor button as you move the throttle plates. It is not the lean/rich screw or the intake air bypass screw. Adjust it with an ohm meter or the 2 lights method.

 

there's a good writeup somewhere that I used... gimme some time and I'll see if I can find it.

 

I couldn't find it... I might have it at home somewhere. somebody else linked ME to it, so I know others have seen/used it, too.

 

Several causes of backfiring but 2 main ingredients.....air and fuel. When you remove a cat, or gut it, there is more unburned fuel in the exhaust than with a well-functioning cat. Anything that is making the mixture excessively rich sets up a dynamic for backfiring. Excessive oxygen entry from leaky exhaust gaskets, bad air injection control valves, etc. adds to this. My N/A backfired every time I accelerated hard until I got my 5th/6th ports to start working again. Rarely backfires now and just barely when it does. Hailers is right, the tps plays a major role in shutting off the injectors on decel if adjusted properly.