Backfiring on stock SR20DET, didn't use to..always had open BOV...help

[junk240sx]

I have open BOV and many say that's why it backfires. BUt it's never backfired before. Now, when i let off gas and start slowing down in gear, it backfires constantly.

I don't think it has anything to do with BOV because it should only backfire once when you let off the gas pedal and BOV releases a bunch of air. Plus it didn't use to do it.

So I'm wondering why it would happen now? Could it be because the timing got skipped a notch? What other possibilities are there?

[Fenvy]

after I did my sr20det swap, I was still running stock exhaust... no backfiring and the plugs show that I was running lean. phase2 was concerned and told me to get exhaust asap

after I get my exhaust, it start to backfire, especially when I let go of the throttle, plugs read normal

backfiring usually means your car is running rich (too much fuel, too little air). It could be that your bov vents already read air and cause the ecu to think that there is more air then actually is. If your bov can be recirculated, do so... or you can try to stiffen the spring alittle to see if the problem reduce a little. Don't do it too much though, yesterday I soften my springs by 2 rotation and my car stalled after blow off, that means losing power brake/steering: dangerous!

[junk240sx]

well like i said, BOV has always been vented and always drove fine except for the occasional backfire. now it's like a backfiring machine gun if decelerating in gear. I'm thinking it's more than just the BOV venting...any other opinion?

[mynismo]

backfiring upon decel is usually a sign of running lean. i could be wrong...

[junk240sx]

I'm pretty sure that's the opposite. Backfire usually is accompanied by 'fire' because it's either running too rich or the timing is off enough to where the igniting of the fuel is the same time the exhaust valves are open.

Only problem with me is trying to figure out what could have suddenly changed to cause this.

I have the SFM for s14 SR20DET except somehow the page for diagnostics on 'backfire from exhaust' doesn't exist. It's overlapped with page 102. Does anyone have this section available?

[Ralph]

boost leak and/or fouled out spark plugs. Change plugs with proper gap and all should be good or at least...should give you a good start.

[Ralph]

Also, what side is the bov on, hot or cold?

[junk240sx]

I could change spark plugs...any reason to why that would cause backfiring though? I just want to make srue I'm not wasting money...things can get expensive if you just keep trying to replace possible suspects...

My BOV is on the cool side.

[Fenvy]

just go to autozone/kragen and buy the 2$ ngk platium plugs for 91 sr20de, gap them and try again

check out this for some spark plug info...http://www.ngksparkplugs.com/t...ry=US

[Ralph]

Backfiring is usually caused by running rich...if your running rich you probaly fouled out your plugs, depending on how rich your running. Or even so, take one out and look at it, you'll know. Running an atmospheric bov can also cause backfiring here and there, depending on what side you put the bov on. If its on the hotside I believe its common to backfire everynow and then without a tune, if its on the cold side, you shouldnt have any problems with a stock setup MAYBE a hiccup here or there. Make sure you dont have a boost leak which would in turn make you run rich, which would in turn make you foul out your plugs, leading to....backfire.

[lee_harvey]

mine backfired like crazy until i invested in an inline fuel pressure gauge and a nismo FPR.Now everything is happy, happy.

[junk240sx]

Thanks. I'll take a look at the plugs today. I don't like the popopopopopopop sound when coming to a light. I have to take it out of gear to avoid it right now.

Backfiring is usually caused by running rich...if your running rich you probaly fouled out your plugs, depending on how rich your running. Or even so, take one out and look at it, you'll know. Running an atmospheric bov can also cause backfiring here and there, depending on what side you put the bov on. If its on the hotside I believe its common to backfire everynow and then without a tune, if its on the cold side, you shouldnt have any problems with a stock setup MAYBE a hiccup here or there. Make sure you dont have a boost leak which would in turn make you run rich, which would in turn make you foul out your plugs, leading to....backfire.

[chickentendah]

mine backfired like crazy until i invested in an inline fuel pressure gauge and a nismo FPR.Now everything is happy, happy.

I'm sure we'd all learn from your experience here. (I run open bov, walbro fuel pump, and stock FPR). Elaborate please.

I have not installed my Nismo FPR yet. But, what did you do to your fuel pressure setting?

[junk240sx]

Just to reiterate my problem. It worked fine and rarely backfired with vented BOV until recently. I wonder why it worked fine until now. I'm gonna check my spark plugs later tonight to see if that was the problem...

[Ralph]

Discount Auto BK6RE gapped to .028 $8ish bucks or so. I think that is your problem if you did nothing different at all and out of no where the car starts to backfire. I usually change my plugs when I change my oil, if not every other oil change no matter what condition they are.

[junk240sx]

Ok, so I put new plugs in and it's still backfiring like a mofo. But again, only when decelerating in gear. I checked timing and it's right at 15. Nothing has changed....any other suggestions as to why it is starting to do this?

[SpeedRacer1]

Plugs gapped properly? Try changing the timing to see if the backfire fades. Check ECU for any codes at all? Sometimes the engines just begin to run different in colder/warmer weather. Also have you actually had someone ride behind you to spot any actual fire? It may make cracking sounds and some poping but when it fires you can feel it pretty good.

[Ralph]

My second guess would be that your maf might be on its way out. Try running it to redline under heavy load and see if the power feels like its still there...its hard to determine without checking the air/fuel but that was a problem I had...my bad was going bad and I never knew it. It started backfiring one day and just got worse and worse but drove ok. All of a sudden, after 5k or so, I could notice a significant lose in power. One a/f dyno pull and I was dumping fuel like a mofo after 5k causes lose in power and backfiring like a champ.

[junk240sx]

Well it idles rough now and lost quite a bit of power. Also burning fuel like crazy. I will check the MAF using the SFM's instructions.

I was also wondering if maybe one of my coil packs went bad. What do you think? Since it idles kind of rough now, I was wondering maybe if...never mind. that won't explain why i'm burning os much more fuel.

Could it also have anything to do with my fuel pressure regulator/injectors? It's still the stock ones but maybe one of them is broken? Like an injector stuck open or fpr not doing it's job?

** On a side note, I retarded the timing to a little below 10 to see if it still backfires and it does. So it's definately not backfiring because of a timing issue. I'm thinking somehow I'm just getting WAAAAY too much fuel into the engine. ***

[lee_harvey]

I'm sure we'd all learn from your experience here. (I run open bov, walbro fuel pump, and stock FPR). Elaborate please.

I have not installed my Nismo FPR yet. But, what did you do to your fuel pressure setting?

the presure should be @ 44psi with the vacuum line off. when its put back on it should go down to around 36psi. my bov is a greddy type s. with a stock FPR i was running at around 42psi with the line on(assloads of backfire). install was so simple is was 1st grade level.

[nismostate]

im surprised nobody mentioned anything about the o2 sensor. it might be because your o2 sensor has gone bad. mine has been running rich lately too. im planning on rechecking everything, test out the o2 sensor, and get a safc.

[junk240sx]

I wasn't throwing any codes but i'll check again.

BTW, now things are WORSE! I don't have any power if you press on the gas any more than maybe half an inch. I know I'm not leaking boost because i'm definately building boost..all the way to 6psi (what I have set at). But any more than 1/2 inch on the gas pedal and you just loose all power even though turbo is spooling more and more.

Any clues? Bad MAF??? HELP!@!

[junk240sx]

Ok, so I AM getting codes....code 11 and 12. 11 is cam shaft position sensor. 12 is Mass Air Flow sensor. That could very well describe all my problems...what do you think?

[nonvtecaccord]

this exact same thing happened on my friends tsi, yes its a talon but has about the same engine management system. it was a bad maf.

[junk240sx]

Cool. THanks for the reassurance. I'll try another MAF just to see if it fixes the error codes as well as the problems.