soooo my car randomly backfires wen i shift into 4th. wen i say random i of course mean it does it wen it wants but it only does it wen i shift into 4th. sooo i was wantin to kno if ne1 knows wat causes this and how can i fix it????

thanx.

 

any codes?????

 

none. iv only had 1 code since i got the car and it was because of my o2 sensor. but its backfired since i got it and iv had it since april last yr and lik i said,that bak fire has never set off a code.

 

Have you checked your timing? Done a recent tuneup? Have you checked for vacuum leaks?

 

i was actualy thinking of wen i did my last tune up early today and realized i need to that. lol. but wat concerns me is the fact that wen i got the car i had to retime it cuz it wldnt start, so im concerned that there mite be somthing wrong w my timing chain and or distributor shaft. cuz the previous owner said he had been driving it evryday for bout a month and he went across a intersection and it just died. and i noticed the timing chain gaskets r new and i had 2 turn the distributor shaft bout 180 degrees to get it started.

 

A loud backfire, or just a little popping noise? Mine will do a light popping noise when I shift to 2nd, sometimes third. No codes, and timing is right (just changed the chain). I was told it's normal for manuals to do a little pop here and there?

 

loud enough for me to hear it in the car with the radio on. i had a friend following me home 1 night and he said he saw the glow in my exhaust from the flames traveling through it.
and is it really normal for manuals to do that?????

 

I think I asked in a thread on here a year ago, but I can't recall correctly. I think they said it was normal...but if your's is that loud...I don't know. Maverick will chime in again, listen to him.

 

well its loud enough that i can hear it over my radio,but wen i hear it ovr my radio,i lik barely hav radio turned up.

 

and iv been waitin for him to get bak on and reply bak. lol.

 

It did it a couple times after I changed the timing chain, and got it timed right...then my fuel pump failed...but I doubt the two are related, I just thought it had to do with the pressure of the exhaust after the clutch going in and what not. Just that sudden change making it "pop"

 

well if it helps,i do hav a fuel leak coming off the line straight from the tank under the car,and strangly enough my car still runs rich, and i hav an exhaust leak. so i dont kno if those hav ne influenc on the backfire or not.

 

The deal with the manuals differs by the car itself. Some do it, some don't. Mine hasn't yet, but, in the almost 4 years I've had the T5, it's only been the last 6 months my idle air controller has worked right, the last year that I've had the proper ECM chip for my year, and I still have a problem with my MAF that actually raises the idle speed when letting off of the clutch. Anyways, you're not really backfiring when this happens. It's actually burning in the exhaust.

Personally, I don't think it's so much backfiring as it is improper shifting... My buddy had a '93 Daytona that he almost never shifted right and it would make that noise every time he shifted. When I had the car, it didn't do it (I'm pretty sure, anyways). It seems to me that it's in the individual driver's technique as much as it is in the tune of the engine. Also, some of the reason this happens is because of what happens when you release the clutch. If it were possible that we would slowly release the throttle as we released the clutch, there wouldn't be a problem known as a hydrocarbon spike. Think of it this way: You're going down the highway at 70 MPH (because I KNOW none of us does the speed limit, right? ), and something happens in front of you that requires you to slam on your brakes. Around 70, the engine is turning about 2350 RPM (or something like that). When you release the gas quick and slam on your brakes, if you release the clutch, your throttle plate SLAMS shut. Your fuel injectors have been pulsing to maintain AFR at that speed, and you cut off the air supply to the engine, instantly causing the AFR to go massively rich. This hydrocarbon spike has to burn somewhere, right? If it won't burn in the engine, what's the next hottest place down the line for it to burn? The catalytic converter, or the most restrictive part of the exhaust.

wesley, check your cam timing. It requires careful removal of the timing cover, but you need to make sure your cam is on time. Also, check your mass airflow sensor. Mine is bad right now, and that is why I'm running so rich, even with 3 sets of fuel injectors. Exhaust leaks also have an effect on the air/fuel ratio depending on where they are. If it's near the engine (before the O2S), get it fixed, as this affects how your O2S reads the exhaust stream.

 

thanks alot for the help i appreciate it,that helps me out alot. and my exhaust leak is actually coming from the exhaust manifold gasket. and its leaking cuz the guy who had the car b4 me tried to change the gaskets and wen he did he striped the bolt holes just enough that the bolts will go in but tightin down but yet they wont fall out. and he striped the two bolt holes closest to firewall on the driver side exhaust manifold.

 

FYI, stock, there are no exhaust manifold gaskets. It's when they are removed for a repair or something that gaskets are used. You'll want to rethread those bolt holes and get that leak sealed before anything else. But, you might want to check your MAF anyways.

 

sweet deal. thanks again for the help,i really appreciate it.

 

Yes, what Maverick said...haha.

 

he seems like a pretty good guy. im glad you both helped me out,thanx.

 

I'm gonna get some fact wrong on this and someone will point it out lol.

When the engine decelerates rapidly like during a slow shift exhaust gasses may be burning longer than usual coming out of the ports. As we know with A.I.R. injection that if air is injected into the mixture it will continue to ignite outside the head's exhaust ports.

When you are running rich (like when your exhaust or especially your manifolds are leaking air) you will accumulate a rich mixture of exhaust gasses upstream of the cat. If your cats are hollowed I have heard that a puddle of fuel may accumulate.

Well, during the shift - or if you rev the engines on some cars and let off the pedal - the exhaust mixture gets a bit whacky because the whole rich/lean situation and the still burning exhaust coming out of the ports ignites the charge in the exhaust system.

So while it could be an indicator of an exhaust leak (letting air in), stuck A.I.R. or a natural occurrence it's not causing a problem AFAIK. But if it occurs all the time you will probably want to investigate either your shifting technique or your exhaust, O2 sensor, or something else causing the richness as a constant rich condition may overwork your CAT and cost you big bucks at the pump.

I had an old 89 2.8 FWD motor that always did it when you revved it and let off the gas. Those motors use DIS so they have a waste spark so they are even more likely to ignite something lol.

I'm sure that one cylinder misfiring could have it's exhausted charge ignited by a nearby cylinder's still burning exhaust as well. Fun stuff.

 

Your post holds true. Just some additional info:

And, if this gets too severe, your cat can EXPLODE. I can post up a pic of one from one of my textbooks if you'd like to see this. I saw the remnants of the cat in person, though (one of the instructors at that school was the one who wrote a majority of our textbooks ).

Now that I think about it, this instance DOES seem to occur more on FWD vehicles... Hmmm.

 

"And, if this gets too severe, your cat can EXPLODE. I can post up a pic of one from one of my textbooks if you'd like to see this. I saw the remnants of the cat in person, though (one of the instructors at that school was the one who wrote a majority of our textbooks )."

I would imagine that the CAT would have to be inhibiting exhaust flow quite a bit before that would occur though. Probably a failing cat that pooled fuel like a hollowed cat, that combined with the fact that if it was failing it was probably clogging and - boom. lol, just a guess.

EDIT: Actually that would make a lot of sense - car running rich, destroys cat, cat partially plugged and not functioning as a catalyst, unburnt fuel pools at bottom, the plug is just enough to hold the pressure and boom.

 

I don't remember the circumstances around it, but I do know there was a pool of fuel in the cat (or near it) and a misfire in the exhaust set it off... I'll look it up in a little while.

 

i mean lik i said i do hav a exhaust leak and im guessing,now that iv read ur guys post, that the exhaust leak is contibuting to the so called back fire. and my o2 sensor hasnt gone off since prolly lik the end of oct/begining of nov this past yr. and that was just from a 30 min drive. well wen i moved bak to troy,mo from indianapolis,indiana i was expecting the o2 sensor to set off my engine light and it never did. so i dont wat to think of that. oh,and my cat is punched out. shld be something i shld b concerned about??

and id rly lik to see that pic of the exploded cat maverick h1l,if you wldnt mind posting that pic up.

 

Hollowed out CATs are a good thing, unless you have emissions. My state dropped emmissions for OBD I cars in late 2008. Kinda seems like they never should have had it. The testing was more strict for OBD I than it is II - OBD I had to go for a "dyno" run with the probe. OBD II is just an ALDL plug-in to make sure the computer says everything is okay. I dunno about you but I'm sure I could make the computer say everything was okay a LOT easier than make an OBD I car run clean on the dyno..

A hollow cat won't necessarily screw you for emmissions, it depends on the state's levels for the particular car, how the car is running, etc.. I've had hollowed cats and passed fine on other cars, never tried it with my TPI. (Don't have to now though )

 

Actually, from what I've seen, there really isn't that much of a difference between a hollowed cat and an untouched cat... As far as I can tell, if you can see right through it (and you can in most cases with newer, non-pellet cats), then you don't necessarily need to worry about backpressure. Besides, they DO make high-flow cats.

I keep wondering if Ohio still runs the dyno sniffer test. They did when I went to school there in '04, but they were talking about getting rid of it even back then. I'm kind of glad I live in NY, except I feel sorry for all those down by Long Island, who HAVE to go through the dyno sniffer. It's nice, except for the crappy oxygenated garbage gas.

Don't worry about the cat. Unless some jerk-off of an inspector decides to do a little probing with a pyrometer (infrared high-temp thermometer) on the inlet and outlet of the cat and finds out they are the same (should be a minimum of 10% difference between the in and out), you'll be fine.