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Evo misses while crusing


Mrb00st

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i have a 2003 evo VIII, when i am going down the road cruising at 3-4000rpms, my car will suddenly start missing. If i let off the gas and get back on it. the miss will go away and then come back. It does it i would say 90% of my town driving. It only does it when i am in the 3000 - 4000 range and if my foot is steady. Once the miss starts, i can flat foot it and it will miss all the way to redline. But once i let off the gas, and get back on it. it goes away

 

just so everyone can under stand what i mean by the miss, basicly when it starts the car sounds like a WRX or something of that sort.

 

So far i have changed, Spark plugs, Wires, Coils, Mass Air Flow Meter. and done a boost-leak test

 

The mods to the car are 3" TBE, injen upper ICP, greddy Profec-b II, 3" Gm Maft. other then that the car is stock.

 

Any idea's would help greatly!

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i have the plugs gapped to .23 i have tryed more and less gap. still does it

 

i have reset the ecu. many times. lol

 

i have a gm maft. its set to stock. but i cant do a wholelot with it due to not have a wideband (due to lack of money from trying to fix the damn thing)

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Why are you running a MAFT also?

 

edit: I somehow missed your mods in the original post. I see them now

 

My car was running a MAFT setup when I got it, and its not worth the hassle. My advise would be switch back to a factory MAF. Which I also have one sitting in my garage, with an intake. Get a Tactrix cable. Throw in a factory tune, then contact someone like Dynoflash, Mellon, or TTP-engineering, who can get you a good email tune that you can flash the ECU with.

 

If you can make it to Cambridge I can throw the stuff in for you and put the factory flash in it.

 

The MAFT is 99% your problem, and your car has NO need to have one

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The car has had the miss sence i bought it. It had the stock mas on it. i have the stocker laying in the back seat

 

my intake temp sensor went bad, so a 3" maf set up was cheaper then just buying a stock mas.

 

brandon at ips hooked it up and drove it. they said the logs were fine on it?

 

my mods are, 3" TBE, injen upper ICP, Injen Intake, greddy Profec-b II

 

i am thinking about taking it brandon @ ips and letting him dyno tune the car. i'm not a big fan of email tunes.

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Dyno tunes are WAY better, no question. You need to get your problem fixed first though.

 

Invest in a wideband and a tactrix cable. Then you can drive around and log the event when it happens. Then you should be able to pinpoint the problem.

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have problems with the 4G63?

 

Loss of power at 3k RPMs and above when cruising at 40MPH+??

 

You sir are in need of...

the barometric pressure sensor trick!

 

Got me curious. Sould we take this seriously, or is this really something that needs bypassed. If IPS drove it and couldn't tell I am awfully leary about this problem. Sorry to say that it sounds like you just inherited someone else's mess. Good luck with that.

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I still believe a full log with mitsulogger, including a feed from a wideband will lead you to your problem.

 

I'm also willing to bet your long term fuel trims are out of whack, if your MAFT wasn't tuned with a wideband. Narrow band is useless for ANYTHING other than a stoich condition.

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My car has been doing this forever... I have no clue what it is and it drives me up the wall. It will start doing it every once and a while and it will not go away unless i throw it in neutral and shut the car off for like 5 seconds. Then it won't happen for a long time, or at least for the rest of that commute. The thing that worries me is that my wideband goes off the scale lean when it happens so I never get on the gas when it does happen. It has had me stumped for a while.
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what throws me for a loop, is it will only do it if i have running 3000 - 4000rpms.. no other time. and once it starts doing it.. u can hold it the clutch and WOT and it will do it to redline, but if u let off the gas, it will go away for a few seconds.
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This may mean nothing to you mitsu guys but obviously I run a chevrolet MAF on my Camaro, it's around 3000 rpms that my fuel trims get a little out of wack. I tuned it out but I had to change the curve on the MAF table in this range more than the rest. I may be on to something, maybe not, but this really sounds like a tuning/parts compatability problem, some fucked up Mitsu only sensor, or something so simple its staring you in the face. Wish I was more experienced in Mitsus that really makes me curious.
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well it has nothing to do with the gm maf. its been like this sence i bought the car. when i got it, it had a stock mas on it. the intake temp sensor went bad, so instead of buying a new stock mas... i just did a 3" gm mas setup. due to being cheaper. the missed never started at soon as i did the maft setup, other wise i would have just pulled it off
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Guest GMoney

Sounds like you need to check the long term fuel and short term fuel first. I sounds like a fuel issue. I would also check the MAF voltage, and the BPS voltage also, when it has this hiccup, to find out which sensor is causing the fuel to go lean.

 

I am also guessing that was a after market intake on the car when you first bought it right? If so that is the problem... Intakes on evo's are big no, no. Unless they are tuned for them and even then some of them are still junk!

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There are many things that it could be (some of which are things that you already replaced but should be checked again).

 

The first thing I would do is get a factory MAF back in the car. I know you said that the probem happened before the GM MAF but it is going to be hard for you to effectively troubleshoot the car with such a weird variable as that product.

 

As others said, you need to get a logger on the car during the anamoly to see what is happening. Maybe your fuel pump is starting to shit and the car is going dead lean when this happens? You replaced the plugs but with what?

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