Jigapoofy

I have a '85 with a 12a that rumbles and spits on decel. Why does it do that? It will also backfire on demand when I press and release the throttle quickly. Backfiring also occurs when I turn it off, unless I let it idle for a bit.
The parts that I've replaced since I bought it about a month ago are: Distributor cap and rotor, plugs, wires, and the fuel filter. It has a stock header with hollow cats, and a 14x4" Bullet muffler (Which sounds very good btw).
My main concern though, is the rumbling/spitting when decelerating. What could it be? Thank you for reading this
-Greg

BrianHeston

Check out this thread, it talks about the rumbling/spitting problem: https://www.rx7club.com/showthread.p...hreadid=308740

As far as the backfiring on shut off, mine will do this if I've been running her hard. It's also fairly normal as far as I can tell.

You may want to check the plugs, and see if perhaps you're running a little rich?

Hope this helps,
Brian

r0taryr0ck3t

my car does the same but even when it is idling :|

dbtolman

Hmmm... Sounds like an RX-7. You'll learn to LOVE these quirks. Just think of it as a 4 wheeled Harley?

You could use this to your advantage, and mod it to throw fire out the exhaust... Fire on demand, look out tail-gaters!

r0taryr0ck3t

but it seems like im loosing power now that it is doing this, how about you poofy?

Jigapoofy

My car doesn't have the best tires, r0taryr0ck3t. But It can peel out all the way through first gear, burn for about two seconds in second, and chirp into third. I was told that it's the second engine the car has had.
It's not that I don't like the rumbling and backfiring on decel, it's just that of all the videos of fb's I've seen mine is the only one which does that. It's just a concern. Maybe I should buy a timing light?

r0taryr0ck3t

ya mine can do the same burn all threwout first a lil bit in second and chirp in third but it still feels like i do not the power i did, i am thinkin abotu cleaning my carb, timing it and maybe look into a new fuel pump, maybe even headers

rotary_neubie

Mine rumbles and backfires abit too.... as for burning thru gears, I just squeal abit if first and chirp in 2nd.....got an lsd maybe thats why?

dbtolman

My, 85 GSL is capable of peeling out in 1 and 2, then a chirp in 3, but only with bad tires. The LSD keeps me from doing this if I have decent traction.

As for loss of power, haven't noticed at all. Sounds like you could be having one of the following issues below, possibly?

1.) Weak Fuel Pump
2.) Clogged Fuel Filter
3.) Timing Issue
4.) Ignition issue (plugs, wires, cap, etc)
5.) Carb out of adjustment

Just a small list, but what I'd consider the be among the first items to check...