New 04 evo 8. Pretty much completely stock. Really smooth car -has 50k miles. When im going fast and I let off the gas all of a sudden, the car jolts pretty hard. Seems like my friends old wrx was the same way. What do u guys thing? I assume thats what happens when a whole lot of torque is suddenly removed.
Is this ok?

btw, anyone want to buy a skateboard? I need gas money =)

 

Make sure the DV/BOV is not on backward as this will cause the car to shutter/buck pretty bad coming off the gas. 50K mile EVO was likely modded at some point and returned to stock.

The bottom port to the UICP side port to the Intake/Airbox

 

ya its most likely the blov. and also check you ic piping.

 

i vote BOV problem

 

check the ic piping for leaks?
Anyone have a diagram or any usefule info (pictures) of the stock diverter valve so I know what Im looking at? I hear some people talking about reversed bovs but this definately has a diverter valve. Can that be put on backwards? I dont hear the sound of dumping to atmosphere so i assume it is only equipped iwth the stock div valve.

 

DV/BOV they are called the same thing around here.

Yes they can be put on backwards very easily. Like I mentioned the bottom port needs to go to the UICP and the side port needs to go to the Intake/Airbox

 

yeah i would guess look at the intercooler hoses and check ur bov thats my guess

 

When your accelerating really hard and are letting off, are you pressing the clutch in or just letting off of the throttle? This would explain a good bit

 

Yeah, its just the evo. I have a stock (+bolt ons and a tune, see sig). If i get around 14-18 psi and then drop to like 20% throttle (about 10 mm hg vac) the DV will open and there will be a 'surge' or 'buck'. Its even worse now that i tightened the stock DV spring to keep it from leaking (you'd be surprised how much air i was loosing thru that pos). I say its normal for a stock DV. Im used to it and can compensate for it by changing my driving style. Slow the rate of throttle change on a 'down-power' This will prevent the DV from opening, and allow the compressor to slow down by itself.

 

if your bov has a leak to it can also cause this, ive had it happen before under colder temperatures with an old bov

 

my old mazdaspeed protege did this alllllll the time.


culprit - ****ty diverter valve

 

Why is this in the advanced section?!

 

cuz i didnt know where to put it.


Ok I will go look today. A boost guage is probably a great thing tohave huh?

 

Btw... I believe it just happenes If i have 100% throttle and let off completely. I don't do that often except to avoid running over a squirrel =) i hate getting blood on my tires!

 

Yes it's nice to have, however it won't tell you much on your whole reversed bov situation. Either that or your vaccum line is kinked/sliced.