My evo 8 is running on 3 cylinders at WOT, but at idle and normal driving its fine.
It started after i changed to uppgraded lifters but then it was missfiring just allitle just like a half second and then it was fine and this have been coming and going but now its worse after 2 months (yes i should have done something about it earlyer but im very busy at work and so on). Now it runs on 3 cylinder at WOT and i was suspecting vaccum leak or coils or the sparkplug wires to be bad.. But the vaccum is around 50 CM/HG so i guess there is no vaccum and i have changed the coils cuple of times because they went bad.. Any ideas on how to solve this ?

 

I'de start by inspecting the spark plugs, and do a boost leak test. You might want to verify cam timing alignment just in case. When ever I have an issue after a job I try and carefully retrace my steps, and often I will find the culprit doing that. Why did you replace the lash adjusters? What's the status of your timing belt?

 

Il check the sparkplugs tomorrow and check if i can get the tools to doo a leak test.
I did retrace my steps, but i cant seem to find anything.. maybe the seal around the screws to the valve cover or the main gasket around the valve cover is leaking?
I changed the lifters to upgrade them to 3mm lifters.
the timingbelt is brand new and the timing is spot on if you ask me.

 

Check for codes. Which cyl is missing during WOT? Possible valve float. A compression test and leak down test can also help figure out what’s going on but start with the basics and check for codes.

 

I dont get any fault codes and the car only runs at 3 under load, if i rev it in neutral its fine.

 

What exactly are the symptoms that make you believe that it is running at 3 cylinders under load? Usually a misfire under load on a specific cylinder is usually spark related.