I have a stock 2004 Evo VIII, aside from the BOV that was on there when I bought it. It has started to miss or maybe hesitate under boost. When I go WOT, I can feel the engine missing or hesitating a few times throughout the RPM range and it seems to have a loss of power compared to when I first bought it. I plan on keeping the car as stock as I can. Any help with this issue would be greatly appreciated. I may have not described the issue well enough, so please ask questions. Thanks

 

Could be spark plug, happen to me. Hesitate at wot.

 

Can you elaborate? What was wrong with the plug or plugs? Also, what is the recommended spark plug to run? I assume NGK, but what model#?

 

Have you done any data logging when you get the hesitations? Just to be sure that it's not knock ... unless you've already checked that.

 

I don't have a data logger. And this is just a stock Evo aside from the bov that was on there when I bought it. I plan on keeping it stock and just driving it and taking care of it as I have my project in the garage (a 71 Datsun 240Z that is going to get sidewayz!).

 

I have a stock 8 as well (excepting that I'm running a Tephramod V7 rom), and any hesitations I get are knock - according to the ecu anyway. After using some det cans and doing some DMA data logging (even faster than evoscan), I found that most of the "knock" was just engine noise (likely to be the lash adjusters) and adjusted the knock background noise thresholds.

I highly recommend that you get evoscan, it's definitely worth it.

 

did you check your mass air flow sensor?

 

Start by replacing the spark plugs. This is a common symptom when they go bad. I would recommend a set of NGK's.

 

I have not checked the MAF, but aside from seeing if it's dirty or physically broken what would you check?


And as for the spark plugs, I put a set of NGK's in the when I did an oil change 2,500 miles ago.
What model of NGK's do you recommend go in there? What is the recommended gap setting?

Thanks

 

You have mentioned the BOV a couple of times now--so whats the BOV? aftermarket, stock, replacement, VTA?

 

Yes, the BOV is aftermarket. It came on the car and is the only thing I see that's not stock.

 

Just recently I've been having issues as well. When My boost Peaks my evo starts bucking. feels like a fuel cut. my evo is tuned and ran perfectly. i first thought it was a boost leak or bov issues but now i'm thinking about spark plugs. I haven't changed them in like 15k.. I do have NGK's racing plugs. They do come pre gspped. Easy installment. So this never happened to me b4. So do you guys think pluggs is the issue?

 

+1

 

The only thing the scan tool says is wrong is the cat is bad/clogged. Would that cause any of my issues?

 

im assuming you have no cel and if its only under boost it sounds like you probably have burnt out ignition coils. the same exact thing happened to me, under aggresive throttle or over about 18psi itd break up pretty bad but when i drove it normal and under boost it was barely noticeabke he car just seemed a little sluggish. and DO NOT get any aftermarket coils like napa or advanced brands the use the same part numbers as regular lancer coils just wih different plug boots. hope his helps good luck