I replaced my engine in my 84 GSL-SE with a Mazda reman, Racing beat headers, Power Pulse muffler and a K&N filtercharger. Car's been running great except when decelerating when the engine was reving over 4k it would backfire(Loud !! thought someone was shooting at me! ) TPS and all solinoids checked out, I still have my Air pump hooked up and modified to open my secondaries.
I replaced my O2 sensor yesterday and the car runs like a dream.. No more backfiring!

 

Nice. That's funny cause my car is loud as a bike under 4k when the aux ports are closed. Once they start opening my car quiets out. THen again, my exhaust is too big.

Normally it's clogged cats or a bad AAV that causes backfiring..

Did you put one of those cheap air breathers on the end of your air pump to prevent crap from getting in when you put your K&N on?

F-.

 

The air pump intake attaches to the K&N filter charger adapter. No need for an aditional filter. What the AAV?

By the way my backfiring started up again?????????
Back to the drawing board.

 

I wish stoping my backfiring was as easy as replacing the o2 sensor. but i dont even have an o2 sensor??

 

The AAV is the large round cap just below your intake manifold.

It's funny you mentioned your O2 sensor didn't fix the problem. I've been troubleshooting a high idle problem for a while and realized the only thing I changed was the o2 sensor. TIme to disconnect & see.

With respect to your K&N, thought it was a cone, sorry.

F-

 

did you have an bung put in you RB header for the O2 sensor or it came with one?

 

Actually I still have the stock manifold with the O2 bung. (header coming soon hopefully).

See my problem is, my tranny went about 6 months back..I didn't have the time, parts or tools to do it, so I had someone swap a 90 tranny in. I also brought a new O2 sensor by while he was working on the tranny and he installed it.

So it went in with a perfect 800 idle. And it came out with an 1100rpm idle. So I'm thinking it's gotta either be the O2 sensor or he damaged a hose putting it back together.

I've taken apart and cleaned by BAC, ASV, cleaned the TB and readjusted the TPS many times.

F-

 

It had a bung in the RB header.