my car backfires everytime i down shift to slow down. or if im just cruizin on the freeway, and let off the gas it backfires. why is this?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by vtaaakkkk!!! &raquo;</TD></TR><TR><TD CLASS="quote">my car backfires everytime i down shift to slow down. or if im just cruizin on the freeway, and let off the gas it backfires. why is this?</TD></TR></TABLE>

One reason, Frank Stallone.

 

wtf?

 

i dunno...

but...

if u watch the pro scca races on speed, some cars backfire when they slow down or downshift...

eh.. i'm a noob ne wayz..

just my 2 cents

 

Do you have black smoke out the exhaust?

Could be EGR or emissions. Could be timing problems. Check your spark plug wires to make sure they are in right spot or in good condition.
Could be alot of things. Anything from something major to a minor thing.

Does it idle fine and otherwise drive ok and only does this when downshifting? Any other hesitations or bogs or anything?

 

ya it only happens when im off the throttle. and it tends to only do it from 3200to 3500 rpms. so if im at 5000rpms and let off the throttle, as the rpms come back down it will make a load backfire at 3200-3500rpms. i just put i turbo on it. and turbed ignition timing all the way down, to 10degrees.

i understand how gas can get into the exhaust but what makes it ignite?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by vtaaakkkk!!! &raquo;</TD></TR><TR><TD CLASS="quote">ya it only happens when im off the throttle. and it tends to only do it from 3200to 3500 rpms. so if im at 5000rpms and let off the throttle, as the rpms come back down it will make a load backfire at 3200-3500rpms. i just put i turbo on it. and turbed ignition timing all the way down, to 10degrees.

i understand how gas can get into the exhaust but what makes it ignite?</TD></TR></TABLE>

what kind of management, sounds like the tune. if you just lowered the base idle you have more issues than backfiring, or will soon enough.

 

your cat burns the excess fuel after it leaves the cylinders

 

ur running too rich

 

i can't wait till the

"how can i make my car backfire like indy cars upon downshift"

threads to start!!!

 

makin your car poop flames is better mine did it on the dyno once.

 

you are runnin too rich, check ur spark plugs.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Jhonny Ricer &raquo;</TD></TR><TR><TD CLASS="quote">your cat burns the excess fuel after it leaves the cylinders
</TD></TR></TABLE>
i have no cat. so how does it combust in the exhaust with no spark??

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Syndacate &raquo;</TD></TR><TR><TD CLASS="quote">ur running too rich</TD></TR></TABLE>

 

Your exhaust somewhere near your headers is above the heat required for the flash point to occur. You dont need spark just heat and your heads get hot enough to ignite the left over gases. When you let off the throttle the left over gas in the chambers doesnt get fully ignited causing it to release in the exhaust system. At least thats my perspective im not saying im right here either so dont hate me....
Other words your running to rich like they have said numerous times.

 

^^^^^
I think this guy is basically right. Not all of you fuel is getting burned in the combustion chamber and is getting sent out the manifold. When it hits the hot exhaust piping, it ignites.

 

when you let go of the throttle, the spark plug won't spark until its about to die (ECU makes it fire) or your back on the gas, so it sucked in gas/air on its last cycle, you let go of the gas (disabling the spark plug) compression stroke did nothing, it got expelled to the exhaust on the piston's next stroke and ignited since your exhaust manifold and cat are red-hot (not litterally but you know what i mean)

 

What?? so your saying that when my TPS is at 0% the spark plugs dont spark? then how does a car idle.

 

you need to check your valve lash, look at your plugs, look at your timming, if all of this checks out fine then you need to rebuild your dying engine. valve job, valves, valve guides, rings, gasket, etc

just go bring your car to someone and pay some money, or engine will be dying soon.

 

Oh man, not to jack thread but I didn't know it was such a big deal. My car backfires but the engine is still running strong, ngk plugs/wires, plugs look normal, just did timing belt and valvelash adjustment, eating some oil but that's about it...I guess I'll cross my fingers

 

well it could be NUMEROUS things. i dont doubt that your ignition is fine, but dont overlook a burnt exhaust valve/s. Take it to a shop and a 5gas reading on it and maybe a power balance test. An exhaust valve like i mentioned may be burnt(prob not) but that does let raw fuel slip into exhaust port, and with a boost application you are running higher cyl temps which could be burning that fuel in the mani. Ive seen it happen before, but not on a 4cyl. Another question to add is what kinda cam you are using? Just take it to someone with experience and have them spit their 2 cents.

 

Do you have a catconverter

 

I have the poping too on my NA car. It's simply because you don't have a cat. Every cat less car I know makes a poping sound regardless of dispacement, arrangement or number of cylinders.

 

Yea there's no way to fix it, Basically your car has to return to idle during that time it doesnt ignite the spark plugs so it will send out feul air ratio. Ive got a 96 cx with some gay exhaust from autozone that the guy before me put on and it does the same thing. Its nothing serious and its not hurting your engine, If you really want to get rid of it. Honestly I think your going to have to get your ECU reprogrammed but i doubt that would even work. The only reason your hearing the backfiring now is because you have no real muffler. With the original setup the stock muffler has baffles that the sound hits wich quiets the backfiring when it occurs. With the performace exhaust its basically like blowing up a firecracker in a tunnel if you get the idea. Gl anyways and have fun


Modified by soundpsych at 10:02 AM 8/1/2006

 

Thanks for clearing that up, I was a little nervous about that whole dying engine thing...that wouldn't be good right before school starts.