annoying problem..
 

so this problem has been pissing me off for awhile now. when, and only when, my car has fully warmed up, i sometimes get a backfire when i shift it at around 4000-5000 rpm from first to second. anyone have an idea why this would happen? also i notice it happens more if i let off the gas a little right after switching gears. for some reason when its not fully warmed up, this never happens. does anyone have any idea?

It probably because it is still in the warmup stage and running a bit rich yet.

so you think the car is running a bit lean after its fully warmed up? the timing is stock, otherwise that would be the first thing i took into consideration (not that im still not). also its a SD car still, its not converted yet, but i havent done any serious engine mods to throw it off(its stock except for u/d pulleys right now). the exhaust im running is just an o/r hpipe and 40 series flowies. i know since its still an SD car they can get finnicky if you are putting on mods changing airflow and such, but i really see no reason (from whats done to the car) to make me think its something i did. thanks for your input, could you explain further?

nothing wrong with the speed density cars, imo they are less finicky than mass air (that's why i will not convert mine)....

my guess is that you are not getting the problem when it is cold because the car is in closed loop, after it warms up and starts taking what the sensors are saying into consideration i'mwilling to bet it's not liking what the o2 sensors are reading. i always hear about people having problems after they've swapped to an off road H or X pipe. my buddy actually had to grind down where the o2s went in so they would read proper (weren't far enough into exhaust flow). try putting the stock h-pipe back on (with your mods it'll prolly feel a lot torquier with the stock h-pipe cause you've lost too much back pressure with the o/r one) and see if it runs better. if not, try putting in some new o2 sensors.

thanks for the help. yeah i am planning on changing the o2's soon. as for the offroad pipe, i had this problem before i had the offroad pipe on it. so i am thinking that you're right about the o2's. maybe i will consider pushing them in further if i change them and dont get the result i want. im also checking my timing tonight to see if that cant fix anything. as for sd cars, i know, ive heard the same things. problem is i don't want to have to take it in and get the value's in my computer changed everytime i do a modification. i have heard they are less finicky as well, and ive also heard some people say you can get better performance from one as well. thanks again for your help, i'll try that o2 trick for sure.

the only time you'll have to change the puter on a SD car is if you change the injectors or cam, and i know people that have gone to 24lb injectors with out touching the puter....you don't really need to worry about it for a long time. i'm sure i'll be running 11s SD with no computer work lol

really? what about heads and stuff? i heard if you do any minor things it starts to throw it off. such as cold air intake (figured that would be okay tho) and heads, cam, intake. i figure cam/intake would be the ones to throw everything off.

This is an old school problem with an offroad pipe and flowmasters...At least it's worse with offroad pipes, but is common on flowmaster mufflered stangs.
What's probably happening is that there is unburnt fuel that is hitting the mufflers and when you let off the heat in the mufflers burns up the raw fuel. It's more of a nuissance than a problem. I wouldn't get too concerned over this.

How many KM's on your motor?

You running headers as well. EGR still hooked up?

would change the O2's first

stock headers. car has 170,xxx on it. and yeah im not too concerned about it, but it sounds hella beater when it happens :LOL: . i want to fix it if at all possible. were there any solutions for the oldschool problem??

stock h-pipe and no muffs....that's my solution for the best bang for your buck exhaust ;)

i wonder if i got a new catback setup.. hmmmmmmmmmm. it just sounds SO beater when it happens, i have to figure this out.

That would probably work, the shape of the flowmasters lends well to raw fuel sitting in puddles in them.
You've checked your timing first though? How many miles on your car? Worn timing chain can cause it to backfire as well but by the time there is enough slack to make it backfire, the car will usually feel really lazy.
I'm also a fan of the speed density system, I wouldn't swap it out unless you are going to do a cam. Even then, I'd consider having a chip burned on a chassis dyno to make it idle properly rather than go to mass air. The Mass air system is good for adaptation, but the speed density cars run harder.

red82 is exactly right, and IMO Mass Air cars aren't really that more adaptable than Speed Density, if you change injectors you have to have the MAF calibrated for it :rolleyes:

There are some great sounding and performing cat-backs around.
:tup

I dont think your problem stems from running Flowmasters, thats the most ridiculous thing I have ever heard (no offense). I've had Flowmasters on many of my cars and I've only had the backfiring issue on my best friends '95 when we switched to an off road h pipe and only on a hard downshift. That was fixed when I installed a pair of new 02 Sensors. I've even had a speed density vert that ran great with a K+N, B-cam, shorty headers, off road H pipe and Flowmasters and the car never backfired.
By backfire are you talking about a loud POP or a series of pop-pop-pop sounds?
SS

it seems that after i put a new spout connector on, it corrected the issue. or it hasn't happened in a long time since then, and its just a fluke. you ran a cam on a SD car and didnt reprogram the computer?? most people make out the SD cars to be so finnicky if you don't convert, but since talking on here it seems you can do almost anything without mass air.

Well, to be totally honest with you its hit and miss sometimes. I've run several cams in SD cars without any problems, and a few others wouldnt even idle. The B cam seems to work well with SD because it has 114* of lobe separation. Not my fav cam, as I hate all letter cams but it works. Crower makes some fantastic cams, I believe one is a 51110 or something with about .480" lift, 220* duration and 114 LS. Works without flycutting the pistons (87-95) and performs great even with stock heads, obviously works great with some more work and usually you can get away with keeping the stock SD comp. You can do alot to your car without having to switch to MAF or even getting a chip burnt.
SS

thats good to know, because wasting money on mass air when i don't have to, sounds like a crappy idea. for that money i can throw in some 410's. it would be awesome if someone had some sort of database on what components work well with SD cars and which don't :D. I'm sure many people (like you) have that knowledge in their head, but it would be great to have a list, maybe I'll look around the net.

i've never come across anything like that, it just takes some experience....knowing what others have done, what's worked and what hasn't. you've also gotta be a little picky about what advice you do take and what you don't. personally i'd rather assume something will work if someone says "yeah, i did it on mine....here it is", that the advice of someone who says "oh yeah, you just can't do that to them"....seems obvious when i put it like that lol

Hey StangSeller,

I have a 95 GT and get the same problem with my car when I downshift, all you hear is pop-pop-pop.

I this a damaging problem for the car? Can it be easily fixed?