Excessive backfiring

[zachattack_5491]

I've been hearing a lot of backfiring lately from my basically stock redtop. It's been getting worse and worse as time goes on. Seems to be worse when it's cold or rainy outside.

I used to only get small backfires on decel while still in gear, but now I get huge ones on decel and small ones between shifts. I haven't checked timing since I put the engine in, but it should still be correct.

I just checked the FSM and it said the only diagnostic for an exhaust backfire is the ECU temperature sensor. I already had that as a suspect because my car was driving weird like it was cold, so I swapped it with the one from my KA which is only about 6 months old.

Could all of this be because I put in a colder thermostat? I'm using a Mishimoto 60c IIRC. Is there any way I could trick the ecu by throwing a resistor or something into the circuit. Any help or opinions would be appreciated.

[PyR0NiAk]

I'd check the timing first... Your colder thermostat shouldn't cause an issue..

[Sideways~S14]

Are you running a blow off valve? If so is it recericulated or Is it vented atmospherically. I know my buddys car used to back fire super loud and shoot 5 foot flames when his bov was leaking.

[zachattack_5491]

Sorry I didn't get an email on the reply to this thread. Yeah I'm running stock recirc.

I'm pretty sure my problem is that my O2 sensor is dead from getting power constantly, and my spark plugs are some stupid multi prong things. New sensor and NGK coppers on the way, so hopefully that will fix everything.

[Blown240sx]

An O2 sensor on a OBD1 SR isnt going to make much of a difference. I unplugged mine and left it unplugged the entire time I had my SR which was 2 years. Never had an issue. The Narrow band O2 doesnt feed the ECU much information and the little correction it might do wouldnt be enough that you would notice.

Id say the guy above is prolly right. You probably have a BOV leak because mine did the same thing when it was stock and wasnt recirculated. It would backfire big time on decel still in gear and would pop between shifts.

[zachattack_5491]

Really? Well that sucks. What do you mean by leaking? Like it's not holding pressure? Or it's leaking some of the air and not recirculating it? I guess I'll go look at it right now. Should I take it off and check it out or what? I've never done anything with BOVs.

[Blown240sx]

What BOV are you running?

By leak we mean the BOV is leaking pressure and loading on fuel or its not recirculated and its on a factory ECU with no piggyback or rom tune.

[zachattack_5491]

Fully stock 40k mile BOV on the SMIC.