I just got my Evo two sundays ago and I been babying that car until today. Here is my problem, if I accelerate from a complete stop, the car runs fine. BUT, when I go on the freeway speeding up on 3rd, 4th, or 5th, the car jerks when it boost to about 1.2-1.3bars (around 5-6k rpm). To describe how it feels like, think about you flooring your car and when the boost is building up, you let go of the gas pedal for a second and immediately flooring it again. My car only have 850miles, anyone can tell me what I should be looking for or should I just bring it back to the dealer for service. I would rather take care of it myself cause its hard for me to find time go leave my car at the dealer. All help will be appricated. Thanks BTW, I live in cali so I have to use **** water 91 gas in my car.

 

hmmm...and no CEL? (check engine light)

 

no lights....the car seems to run fine if i don't push it.

 

I wouldn't do anything except take it back to the dealer. You have a warranty, it's virtually brand new, take it back and make them fix it.

 

does ur rpm move up still smooth or does it stay the same for a bit then go back up or even go down a bit...... if dats the case ... it could be the clutch going.. but i dont see how since u've just finished breaking it in...

 

I don't think the rpm drop. I think it feels more like a boost spike but I never hit anything higher than 1.3bar.

 

maybe its your engine breaking in?? Heck i dont know

 

It is definetly boost spike. I took my cat off yesterday and it did the same thing you describe. Come to find out I had to turn my boost down. I think you should take it back to the dealership. Dont touch anything man. There must be something wrong with your cpu because it should not be doing that

 

Diagostic test :

Get a can of NOS or VP octane booster - pour in tank

Disconect neg batt terminal for 3 mins to reset ecu

Test drive and report back

 

I installed a blitz turbo timer with boost gauge, do you think the dealer will give me **** about it if i bring it back?

 

The turbo timer no. But the boost gauge maybe. If you tapped into the intake manifold like I did, the dealer can say that you tapped into the BOV vacum hose. So if you can take it off try to. Also I hope you did not splice into the IGN wires to hook up the timer

 

What were the weather conditions when you noticed this? And was the engine only running for a short time (but long enough to be warmed up?) I get this bit of stumble under the same circumstances during cold dense weather, it could be boost spike, or some other anomoly.. But I suspect it may just unfortunately be weather related.

 

I live in the bay area so it doesn't get too cold around here, around 45-50 degrees. It has been raining here for the past few days. I am not sure if that will affect the car tho. I just tried resetting the ecu and went out for a test drive. It doesn't seem as bad as before. I am thinking if my turbo timer has anything to do with it. Maybe I set my peak boost too low or the boost warning too high. I ran an auto peak boost test and I boosted at 1.39 peak. Anyways, I will try again tomorrow when on my way to work. Hopefully the prob will be fixed; I keep you guys updated. Thanks for all the responses, again...all help are greatly appreciated.

 

I have had the same thing happen, It does feel like a boost spike or a letting off the gas and right away full go again. it happens when the weather is cold 50 or less, and when boost is over 20 and at about 90% throttle, It happend for the 3 time today, And it feels like the engine just hickuped really quick, the other thought is that colder air causes the mixture to be more lean thus causing some sort of knock or higher boost pressure from denser air. I had to readjust my boost controller since the weather here in chicago has gotten below 20 today, don't know if that makes since, but i had it set for 20 psi in the fall 40-70 as temps and today when it got 20 the dam thing was up at 23, so i backed it off

 

Uninstall everything and take it to the dealer, thats not boost spike, boostspike is completely unnoticeable, the car should still transistion smoothly as the boost changes.