Hi everyone. This is my second time posting a thread regarding my ride and my backfiring problem. I have a 90 integra with a b16a and 2 1/4" piping and whenever i shift from 1st to 2nd, to 3rd...sometimes to 4th gear there is a loud pop. I was told by some knowledgeable people on here that it could be my PCV valve, my CAT converter since its hollowed out, my ignition timing or my oxygen sensors. I was instructed to replace the PCV valve first since its the cheapest part ($10) , and if not replace my CAT. So i replaced the PCV valve a few days ago and it still backfires. I had a hollowed catalytic converter but I replaced it like 2 hours ago with a brand new direct fit CAT converter and....it still backfires. I was also told by someone on here that if i replace the cat converter and still have problems then its possible that my O2 sensors have gone bad. I've replaced plugs and wires in the past and the backfiring still persisted. I don't know what i should do but I don't wanna waste any more money. I just spent $240 bucks and the problem is still there. Can one of you guys please help me out and tell me what i should do now? Thanks.

 

what idiot told you it was the pcv valve

 

There were several "idiots" that mentioned it could contribute to the problem. If the PCV valve is stuck open, an excess of blowby gas could enter the combustion chamber and increase the possibility of pre-ignition.

 

Couldnt this be a contribution of backpressure ?.. I know my 00 Gt eclipse had a rowdy backfire when shifting gears after I added a Greddy EVO my first week of owning the vehicle from 0miles(Brand New, No mods or motor problems).. Just a thought, not saying this is your solution, But it may not be anything to worry your self over.

 

Theres many possibility's. Does the car burn oil at all?

 

well lets not resort to name-calling please..... nobody who gave me previous advice was an idiot. they know way more then i do when it comes to engines and technical solutions. well i don't think my car burns too much oil.... i have no idea what to do man..... i'll take whatever advice or suggestions you guys feel could help me. i know it's not gonna destroy my ride or anything but its funny cause its like people on the sidewalk act like its a driveby or something. even the cops pulled me over once and asked me what the deal was with the backfiring......now we all know that's way too much attention...

 

alright thanks for the reply. do you have any suggestions for me that you feel could help me with this annoying occurence?

 

Back to basics for a bit, I can't find your other thread about this.

What mods does the car have?
Have you checked your ignition timing, and valve lash?
Are you aware of any leak in the exhaust system, exhaust manifold or intake manifold?

 

What size is the tip you are running ? and is 2 1/4" your stock size piping ?..

I would go with the advice above, timing lash and leaks, and if thats not it maybe it is the cat. There are alot of things that could contrubute to this. I know in my old LS it would backfire with a stock cat, and 2.5" piping, But I replaced the whole system back to a stock style and it got rid of it, pretty much confirming it was an air flow thing. Does your tip have a silencer ? If so, try pluggin that in and listen for it..

Ohh, when you shift, what rpm range does it do this in, or is it all ranges ?

 

What is stated about the PCV valve "could" be true but it is on the lower end of possibilities. To rule this out inspect the air filter and see if there is any burned out looking spots on it. That is a good sign something is wrong with the PCV valve.

Moving on. Backfiring is commonly caused by un-burnt fuel igniting from the heat of the exhaust, thus causing combustion and the backfire. With straight through exhaust it will be more noticeable as well.

1. You already replaced the cat so rule that out. Did you notice a reduction in the backfiring after doing this?
2. If the o2 sensors were bad you would throw a CEL.
3. It could still be running rich which is calling for an adjustment to the fuel supply and a tune on the timing.
4. A resonator and chambered muffler may eliminate this as well. I am saying that because when I had my greddy exahaust it was straight pipe from the cat back into a straight through muffler and it backfired like a bitch. When I switched to the Apexi WS2 it all went away.
5. Have you noticed if the exhaust tip is heavily blackened? How about the paint around the bumper.
6. For starters I would run Honda Top end cleaner though the motor to clean it out good and blow the crap out. Then go from there.

So pick your poison and think what you think it might be with the new info. provided. Everything listed is a possibility.