tuning a misfire out of idle? HOW TO??
 

ok,i have got almost everything working now on my first turbo install. im using crome, 450cc injectors, and an ls motor. cold start is absolutly rank, it misses, pops, and runs rough for a few minutes and then once it starts to warm up its alot better. BUT, when its completely warm i have idle set at 850 and there is still a slight miss. id really like to get rid of it. also shifting between gears i get a backfire. what all causes this? do i need to add fuel take it away or what?

Re: tuning a misfire out of idle? HOW TO??
 

I have the same exact...slight miss at idle fully warmed up. Idling anywhere from 14.0-14.7 it still pops. I have just given up on it. Could be the injectors I am using, maybe...could be something else. I dunno...I have just accepted that I cant 'TUNE' it out for some reason so it must be mechanical...

So many cars I tune have perfect idles...some lope no matter what I do. Idle is one of those things that is so far from cut and dry (and obvious) but in reality your car spends a lot of time sitting there (and you notice every imperfection in that spot only)

O0

Re: tuning a misfire out of idle? HOW TO??
 

yeah hmmm, i dunno. i dont think i can do to much anymore. valve lash is perfect, comperession is pefect. i cant think of anything else. so your tuning between 14 and 14.7. yiikes, i should lean it out a bit. its at about 13 right now. but it seems like the morei lean it out the worst the miss gets.

Re: tuning a misfire out of idle? HOW TO??
 

same here...what injectors are you running?

saturated or Peak and Hold?

Re: tuning a misfire out of idle? HOW TO??
 

450 dsm whatever they are

Re: tuning a misfire out of idle? HOW TO??
 

Sounds like an ignition issue to me

Re: tuning a misfire out of idle? HOW TO??
 

one more thing, about open and closed loop. i should tune in closed right so its not getting the o2 readings so i can see the changes i have made via the wideband. i have 2 bungs welded in by the way. and then once i tune should i drive around in open loop and let the computer find a value for the injector pulse that is somehwere between the values i have? i mean for now im not data logging just trying to remember numbers so its not very accurate.

Re: tuning a misfire out of idle? HOW TO??
 

nope, not ignition, well i mean very unlikely. new distributor. but old wires. i have 3 sets at home and they are all the same. still miss with each

Re: tuning a misfire out of idle? HOW TO??
 

i had the same problem, and just gave up on it because everything els was good but a slight pop at idle.

Re: tuning a misfire out of idle? HOW TO??
 

I got a slight pop at idle too sometimes. Doesn't really bother me.

Re: tuning a misfire out of idle? HOW TO??
 

both my cars had a little miss at idle occasionally...

Re: tuning a misfire out of idle? HOW TO??
 

well now when i go to sell my car the buyer is going to be super sketched out. if i were the buyer id think there is something wrong with the motor. but its in perfect shape, ill just have to explain to him/her

Re: tuning a misfire out of idle? HOW TO??
 

could be, i think my alternator has been on the fritz for a little over a year. over 5500 rpms my battery light turns on...LOL

im too cheap to swap it out and see if a new one takes care of it :1

Re: tuning a misfire out of idle? HOW TO??
 

i sold my car last weekend and just told him that it runs a little rich at idle and when it's cold, he looked at me like :1 so i knew he had no clue what i was talking about.

Re: tuning a misfire out of idle? HOW TO??
 

it is definately ignition issue, as I posted in the other thread about the diffent plugs I tested in my motor, and the colder I go the better the car idles, I am using uberdata with rc750cc, and gm 3 bar map sensor.

Re: tuning a misfire out of idle? HOW TO??
 

That pop when shifting is jdm. Your one of the lucky ones.

Re: tuning a misfire out of idle? HOW TO??
 

mine does this too.

Re: tuning a misfire out of idle? HOW TO??
 

How tight is your plug gap? Just for something to do, if you have a stock set of plugs. Pop them in with a bigger gap and see if it goes away. ;)

Just for some testing purposes.

Re: tuning a misfire out of idle? HOW TO??
 

gap is .028. plugs are a 6 right now

Re: tuning a misfire out of idle? HOW TO??
 

You can do two things to get rid of the popping when using bigger injector.

1 - Richen up the mixture a little
2 - Take out timing until it goes away.

The bigger the injectors are, the less accurate the ecu is when controlling low duty cycles. The injectors flow becomes erratic at such low duty cycles. Saturated injectors are crap when it comes to this. P&H injectors correctly used with P&H drivers can operate correctly at low duty cycles.