Hey, I have a question for everybody that I'm slightly confused about. I know that the less restrictive the exhaust is on a car, the better the flow is, but is it possible that my car is "missing" and "backfiring" because of an exhaust leak becasue its lacking back-pressure? If so, isint this slightly contradicting? Im just wondering because even after all my work the other day on my car adjusting timing, mixture, idle speed so on and so fourth my car does run much smoother, but now when you rev it up and let it drop to an idle again, it has some "poofing" noises that come from the engine. It almost sounds like the engine firing at the wrong time or "backfiring"...Since I have adjusted everything in the manual practically, I was just thinking this could be cause by the exhaust leak my car has (under passenger seat). I wrote a thread on that and got some good help so im gonna fix that soon. I hope you can answer my question. Thanks

~T.J.

 

I think that you are on the right track. My 80 used to backfire because of an exhaust leak.
hanman

 

Well then why would a car "run better" with open headers?

~T.J.

 

exhaust leaks invite fresh O2 into the raw exhuast and when letting off the gas a rapid loss of exhuast pulse pressures causing a moment of vacuum drawing in air were ever theres a leak, more raw fuel is drawn into the exhuast momentarly when the throttle plates shut thus being ignited in the exhuast by the heat and the air drawn in. If you have a very free flow exhuast like a open header that ends at the collector, letting off the throttle will be simialar because there is virtually no pressure when the throttle plates are shut thus drawning fresh air near the exhaust hole and any raw gas there might ignite.

 

yeah, a missing and backfiring isn't caused by exhaust leaks.

AFTERfiring (the correct term for exhaust pops and bangs) is usually caused by vacuum leaks or bad ACVs on our cars.

 

The air control valve is notorious for this... My 80 used to backfire like 5 seconds after I shut the motor off. It was kinda like that old John Candy movie, 'Uncle Buck' LOL

Rev her up to about 3k and then shut it off, 5 seconds later, BOOOOOM LOL

Replaced the air control valve with a blocking plate, and no more problem... Of course no more fun either

 

ok... I have a question. The backfiring im referring to I think is an inaccurate term. I think the engine "stumbling" is a better term. There is no actual backfiring, in the exhaust, but the engine "stubles" every now and then. Almost like its missing, but it only does this when the engine RPM's drop after you rev it up. I was just wondering if this could be related to the exhaust leak...I hope that help in the description of my problem. Thanks.

~T.J.

 

i really doubt that it's related.

 

Ok, well if its not related then what could be causing it? I have good spark on all 4 wires, and Ive gone through practically everything in the manual that would affect the intake of fuel and it still does this. I guess im just at a loss and the only thing left that I could think of was the exhaust problem...

~T.J.