meld

iTrader: (16)

My problems just recently started. Under partial throttle I get this bucking/hesitation but as soon as I go past a certain point in the throttle it clears up and runs just fine. This only seems to occur at part throttle during cruising/putting around. Also at idle it seems like the same issue, rough idle, yada yada. I have been reading around and seems like it could be fouled plugs? bad front o2? IAC solenoid?

Mods:
Cossie Cams
Meth
Intake
TBE
PTE 1000CC injectors
Walbro 255
Magnacor Wires

those are the important ones

any thoughts?

less10

iTrader: (17)

Sounds like you have a lean spot. Do you have a wideband on the car at all?

meld

iTrader: (16)

I have a wideband, and @ cruising its between 14.7-15.2. So thats normal...the car ran PERFECTLY till just a couple days ago.

althemean

iTrader: (5)

leak on a vacuum line? loose clamp? just throwing some ideas out. throttle body leak...

less10

iTrader: (17)

Could be a blown headgasket, pull a plug and see if it has any green tint to it. Or start your car take off your radiator cap, if you see constant bubbles then the headgasket is toast.

evo150

iTrader: (51)

no cel? when is the last time you changed out your spark plugs?

meld

iTrader: (16)

No, no smoke, no green on the plugs, just some orange from some 118 I ran a while back, and thats about it. Hrm...

EE

iTrader: (9)

Do you have an HKS SSQV bov ??

2muchboost

iTrader: (10)

mine did that same thing when i had a Hks SSQV bov on there..
I took it off and installed a recir Bov and the problem went away..

SHIFTT IX MR

Do you have a tune that is appropriate to the mods you have installed? Generally speaking, the bucking, poor idle you feel is either a spike or valley within your powerband that should be tuned out. Smooth power bands result in nearly identical transitions of power from the engine to the wheels.

If you have a good tune, look at your MAF sensor, crank position sensor, and all o2 sensors. Poor idle can mean many thing, including a boost leak, but that is an entire new can of worms, that even I stray from digging into. I have seen boost leaks go on for endless periods of time, sometimes resolving themselves - don't ask me how, I have no idea.

What I would recommend is building a check list that incorporates each and every variable that can affect idle, and engine control. This can be a tedious task, but from my experience, opening the hood of your car will generally confuse you, so you really do need a starting point to asscess your constants, and your variables.

I know exactly what your talking about when you say that at a specific RPM, the engine seems to suffer from a hiccup. In fact, thats probably what it is. Not to scare you, but you could have an electrical short. A Datalogger will enable you to see if sensors are acting up, and what EXACTLY occurs when you reach that specific point. From my experience with my EVO, I tend to ignore indactors of a problem, simply because since my car still has an existing warranty, so long as it gets me to point B, from A, I'll tolerate the car's hiccups. It is when it breaks, thats when I become concerned, but only to the extent that what is wrong with the car, will be covered free of charge. When I have to beg to get repair work performed on my EVO, that should be warrantied, that is when I begin to hate the car I drive. Its as if dealerships use the car's stigma to elude their obligations.

fixem2

iTrader: (30)

Did you figure out the hiccup?