serious backfiring!

[turbocarslut]

My car has recently started to backfire horribly when I engine brake. I took out the plugs and they are white which would mean a lean condition to my understanding. Yet my muffler is black with soot which would mean a rich mixture. I know its not the ignition system cuz there is no hesitation whatsoever when I accelerate. It idles rough though. Any one have a clue?_______

[NiTeRiDeR]

sounds like my carhavent been able to pinpoint it though

im going to take it to my friends shop and get a tune up and adjust the timing (it smells like im running rich)

[turbocarslut]

changed O2 sensor, plugs, oil, and pcv valve...$64 spent and still it backfires...

[Phat_Optimo]

It is alots of pops or 1 loud bang. What kind of car and are there any mods.

[turbocarslut]

I'll rev the engine...and let the rpm's fall..then I get like 4-5 pops consecutively. Or I am in 4th and downshift to 3rd to engine brake then I get the damn pops.

[Toahk]

Replace your fuel filter lately?

[koukis13]

my car is doing the same thing i just put in my header and i accidently cut the wire to the o2 sensor , could that be the problem??

[red240ne]

Adjusting the igntion timing would help, but you don't want to just cover up the problem if the timing isn't it. Does it sound like it's missing? Seeing that you replaced all of those parts, including the 02 sensor, that narrows it down to a couple of things.

Check your air filter/fuel filter. The pressure regulator can sometimes have an effect too. Try disconnecting the vacuum hose from the pressure regulator and driving around. If it gets better, then it may be fuel related.

Also might want to try a diagnostic test in Mode 2 on the ECU. To get it into Mode 2, turn it and hold until you get the double flash, and then turn it back. If you get any flashes then, record the flashes, and have someone with an FSM tell you what those flashes mean. You might want to time the flashes too, like however many there are within 60 seconds. Some are like that, and some are not....anyways, hope this helps.