79' backfire on deceleration above 4k rpm?
 

Hi guys, could someone lead me to a link or give me a little advice? My 79 12a w/58k miles runs good but has a backfire on deceleration above 4,000 rpm. It does have an electronic ignition upgrade. Could it possiblly be the cat. Converter or air pump? Any help would be appreciated. Thanks.

Not sure if the 79 has it, but check the richer solonoid on the carb. Mine came unplugged and caused lots of backfiring on deceleration. Plugged it back in and ran fine. If it is plugged in, I don't know how to test it to make sure it is workign properly.

In the 1980 FSM, it says to remove the richer solenoid valve and apply battery power. The valve stem should be pulled into the valve body with power applied. It is in Chapter 4 page 12. HTH

-Scott

Fix the leaks in your exhaust system. Most backfiring issues are the result of fresh air being sucked into the exhaust system through a crack or hole, then the fuel vapors ignite in the exhaust. :)



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thought this was normal >.>

i agree with Kentetsu. a leaking exhaust can cause backfiring, especially on the SA. you usually only see backfiring when the engine is no completely warmed up and is usually occurs between shifts or when you let off the gas under decel. my 80 LS has a leak in the exhaust and it pops under decel when cold.

also the SA does not have a catylitic converter

on my 79 Mine would backfire if i left it in gear and let it decel (pulling raw fuel through the carb) it would build up and them BOOM...

Thanks for all the advice. I'm pretty busy at work and hope to get to it over the weekend. I think i'll be looking at the deceleration solonoid first. The exhaust is not leaking. My handle came from a problem with a different 7 a few years ago.
Any other ideas? I'll post when i get it fixed.

Decel backfire (more correctly, an afterburn, not a backfire) on an SA with stock exhaust will generally fall to one of these:

Richer solenoid not working
Decel (anti-afterburn) solenoid circuit issues
Air Control Valve going out (the anti-afterburn valve is part of ACV on an SA) or possibly loose on the manifold
Internally fractured upper air duct (first exhaust section after the thermal reactor) or hole inside the thermal reactor
Bad or incorrectly adjusted dashpot on the carb

You will WANT this document...
http://foxed.ca/rx7manual/manuals/19...Highlights.pdf