random misfire help

ryant25bb · Mar 25, 2009, 11:00 AM

its been going on for a while but in first and second gear it seems alright but if im in 3/4/5 gears it will misfire horrible 3grand and above or on the free if i hit boost in 5th gear it will misfire. Its almost like im hitting the rev limiter and when its misfiring if i let of the gas for a sec and get back on its ok. It also runs alittle rough at idle. Throws code p0300 random/multiple cyl misfire. ALso if i give her hell it will misfire really bad for a while after. Some or most of the plugs are pretty white/ lean. And on the airfuel gauge eventhough its like a light show it does lean all the way out when it misfires. I'v gone through plugs,wires,vac leaks,boost leaks vac stays steady at 20 at idle,coil packs,comp test 195pounds on all cyl. ?????

blaze_125 · Mar 25, 2009, 11:29 AM

what's your fuel management?
have you checked it?

mx4life85 · Mar 25, 2009, 11:33 AM

That was the exact same problem I had.

Go one step colder with your plugs and you should be good. I went with the Denso IKH24.

senate6268 · Mar 25, 2009, 08:43 PM

Are you using a wideband or narrowband O2 gauge? What is your AFR at when you misfire at WOT?

blaze_125 · Mar 26, 2009, 06:53 AM

Quote:

Originally Posted by senate6268

Are you using a wideband or narrowband O2 gauge? What is your AFR at when you misfire at WOT?

He's using narrow band, and getting lean when it misfires. It's in the post.

4g94T · Mar 26, 2009, 09:08 AM

Maybe it's the injectors

ryant25bb · Mar 26, 2009, 10:11 AM

all im using for managment is a 255lph pump and regulater. RRm intercooled turbo kit. It ran fine for 3 to 4 years and just started acting up. Its been like this for a year or two now sometimes it would clear up for awhile but no its all the time. I'v looked at it numourous times mitsubishi looked at it and a couple local shops and nobody could find the prob. Colder plus with the same gap.030?

ryant25bb · Mar 26, 2009, 10:19 AM

also when i reset the computer (disconnet battery). I go through all the relearning but it will keep killing at idle until i turn the car off. and then next start up it will be ok Is that normal. I could check the pump again it doesn't seem as loud as it used to be. If i return the car back to stock which i did last summer just to see what would happen it still had rough idle. by rough i mean i can hear and tell but if you didn't know the car you prob wouldn't even notice. but stock it doesn't misfire when driving it, pretty much runs good.

blaze_125 · Mar 26, 2009, 01:46 PM

Quote:

Originally Posted by ryant25bb

all im using for managment is a 255lph pump and regulater.

could your fuel pressure regulator have gone bad?
do you have a way to monitor fuel pressure? Maybe take it to a dyno, hook a gauge on your fuel line and monitor fuel pressure throughout the powerband in every gear? Just an idea... Most people know alot more than I do about boosted cars.

If you got the type of regulator I think you have... it's probably the "raising rate" type or whatever. It increases fuel pressure as it sees pressure in your manifold. After a few years I have no doubt it could fail.

mx4life85 · Mar 26, 2009, 02:58 PM

Quote:

Originally Posted by ryant25bb

all im using for managment is a 255lph pump and regulater. RRm intercooled turbo kit. It ran fine for 3 to 4 years and just started acting up. Its been like this for a year or two now sometimes it would clear up for awhile but no its all the time. I'v looked at it numourous times mitsubishi looked at it and a couple local shops and nobody could find the prob. Colder plus with the same gap.030?

Are you saying you have those installed? Or you want to install them?

ryant25bb · Mar 26, 2009, 04:22 PM

if your talking about the 255pump and vortec fmu yea there installed

ryant25bb · Mar 26, 2009, 04:24 PM

or if your talking about the plugs no im just using the ones recommended from the kit. But if those plugs worked fine a year ago why would a colder plug solve the prob?

ryant25bb · Mar 26, 2009, 04:26 PM

i should get the inj pressure tested. Or like blaze said do a fuel pressure test which i did a few months ago but just at idle and it was fine.

ryant25bb · Mar 26, 2009, 04:31 PM

i should have put this all on the same post but o'well im running about 9-10 pounds of boost which i'v been running since i'v had it. And i by no means baby it im surprised it's held up this long. I checked for air leaks but found none like i said but usually at idle its at 20 inches of vac but sometimes it wil be at 16-17 which im sure is ok?

Jonas · Mar 26, 2009, 07:11 PM

Wow, i'm getting the same thing with my turbo set up... i have the RRM 16G set up with 5th injector set up... the care still has the pretune from RRM... I'm getting missfire at the same places youre getting... the only time i don't get it is when i floor it... is this due an untune car?