so wtf, yesterday while driving, the backfiring shit came back. it backfires when i let off the gas and coast to a stop. i havent changed anything since it went away. the only thing i did was clean out my ML with some carb cleaner, insider and out, the whole thing. i pulled the plugs and they are white'ish greyish which i think they are supposed to be. i believe running lean cause white plugs with little blister looking things on the ends in which i dont have. a guy i work with said they look good which means im running good, but the backfiring went away and now its back, lol, any ideas why?
im running 15psi idle and when boosting on 6-8psi, my FP is around 38-42, is that good or bad? my egts dont seem to be bad though, 900 idle, 1200-1350 cruising highway and abotu 1250 around 40-45mph cruising and boosting, i havent seen above 1450 at 10psi once. dont get it, what do you think? on my afc too, 1k rpm again im at -16%, 2k im at -14% and 3k im at -10%. i have no way of telling what my a/f ratio is yet cuz i dont have my wideband yet in which im getting at end of july so what they hell do i do now? try changing the plugs or what do you suggest? its just odd that i never touched the settings or fuel setup at all and now its back, and back consistantly! wtf :shrug

I woulden't really worry about it my friends lightning backfires all of the time <sounds naasty in a good way>. I dont know too much but if I could guess, Backfire occurs when there is too much fuel being thrown into the motor and it combusts in the exaust if I am not mistaken, maybe you have 2 large of a disc in your sfmu, or maybe you need to change the settings on your safc to lean it out more on decel. BTW do you have a digital a/f gauge, if so what does it read on decel?

reads stoich, 2 bars before rich.

Originally posted by eclipse982nrRST
reads stoich, 2 bars before rich.

Your too lean. I my car backfires all the time off throttle, no big deal unless you have a cat on it.

Shrink your sig, It's way too large.

hotter weather will make you run richer (hence backfire)
colder weather will make you run leaner

Originally posted by etx
Shrink your sig, It's way too large.

x2

ya it seemed to just start backfiring again since its been in the 90 degree range this week. i will richen it up a little bit and see how she does then tomorrow maybe. i hate it, it sounds terrible.

lol, i will shrink my sig tomorrow when i have time :)

Originally posted by eclipse982nrRST
ya it seemed to just start backfiring again since its been in the 90 degree range this week. i will richen it up a little bit...

When its hot lean the car to keep it from backfiring.

cold air = denser air = more fuel needed to fight off detonation
hot air = less dense air = less fuel to keep car from backfiring

so today, a guy came into my work today and he works for a dyno shop about 45 mins away from me. he was asking me about my car and i was telling him about it and what not and i mentioned it started backfiring. he asked my fuel setup and what not and he said that an s-afc's settings are actually different. he said that when i think im leaning out, im adding. this doesnt seem true but hell i dont know, he knows more about tuning than i do. so anyway, on my way home, i changed my settings at 2k rpm that were -10% to 0 and it doesnt do it as bad now. before when at -10, it would putter real loud at decel and backfire super ass loud, now when at 0, it putters, but not nearly as bad and only backfired once unlike every time when at -10. what is up with this shit? lol

If it works.... don't worry about it.

well ya it works, i would still like to know though about the settings.

if your backfiring out the exhaust your too rich
if your backfiring in the intake your too lean.

You will need to tweak that setup from time to time as weather changes.

You can do it at the fuel reg, once you are good you will know 2 different fuel pressures to run. one for winter and the other for summer.

Terry

Im not a fan of the SAFC....messing with the timing too much under load....but that point aside, with large injectors your car will almost always backfire a "tad" under de-cel with the car in gear....it shouldnt backfire loud though....you may be WAY too rich...what size injectors are you running, and what does your fuel management consist of other than the SAFC? what fuel pump? being too rich is just as bad as being too lean, it can hurt your motor just the same.


1997 Silver RS
Built
T3/T4 BB Turbo
20psi
Most current 1/8th mile time: 8.1@93mph 2.015 60'
1996 Black Supra TT
2004 Silver Snake

Originally posted by Nitrous_RS1997
Im not a fan of the SAFC....messing with the timing too much under load....but that point aside, with large injectors your car will almost always backfire a "tad" under de-cel with the car in gear....it shouldnt backfire loud though....you may be WAY too rich...what size injectors are you running, and what does your fuel management consist of other than the SAFC? what fuel pump? being too rich is just as bad as being too lean, it can hurt your motor just the same. 1997 Silver RS Built T3/T4 BB Turbo 20psi Most current 1/8th mile time: 8.1@93mph 2.015 60' 1996 Black Supra TT 2004 Silver Snake

440 injectors, safc, sfmu, walbro 255 intank pump is my fuel setup. 14psi idle pressure, leaned on on afc -16% for 1k, -14% for 2k and -8% for 3k.