My cousin bought an evo 8. When we got the car we chained oil, and done the general maintenance before starting it. We then took it out for a drive to see if everything was working and it was (except for the ayc). When we took it out for a second time it started to misfire when reaching 4000rpm. So we changed the coil packs to a upgraded set and changed the spark plugs but it has not changed a thing. We fitted a boost gauge to see if it building boost and it is, it builds to 10psi then the misfire occurs. When driving it you can tell its going to misfire as it feels sort of sluggish. Any ideas on what we should check next? Thanks.

We had a fault on the tps which is now gone after we adjusted it with the adjustment we made it is now running to 5000rpm and building 14psi of boost before misfiring.

No fault codes are appearing when misfire occours.

Issue fixed it was the fuel pump was starting to go. The evos fuel pump runs on 10v when idling then moves onto 12v under load which is why it could rev to 8000rpm no problem when stationary. Take the car down a hill and see if it will rev past 4000rpm as the fuel pump does not have to work as hard.

 

I'd check sparkplug gap. I'd also take a peak to see if the timing belt skipped

 

sounds like a boost leak somwhere

 

Checked for boost leak was small one on outfeed on intercooler but did not fix issue.

 

Gap on spark plugs was 0.8mm changed to 0.5mm no change.

 

check the wire connection on the plugs of the coil. I have a COP kit and my tuners dont disconnect it when they change sparkplugs so the wire eventually broke. also check that thin ground wire for the cam sensor. these wires get very brittle

 

Did you ever get this diagnosed? I think I'm having the same issue.

 

No we are still working on it we suspected it was the boost valve emission control which is a small valve that connects to the waste gate because we could blow through it from each end but we waited 3 months on that part for it not to work. Did you get your issue fixed?

 

Checked the gap changed it multiple times made no difference. I dont think its the timing belt as when it is stationary the car will rev past 4000rpm perfectly and you can rev her up to 8000 with out any bother.

 

Checked the gap changed it multiple times made no difference. I dont think its the timing belt as when it is stationary the car will rev past 4000rpm perfectly and you can rev her up to 8000 with out any bother.

 

We closed one side off and filled it with compressed air listening for any leaks and we could not hear any.

 

which upgraded coilpacks are these?

 

https://www.gb-ent.com/collections/c...hi-evo-iv-viii

 

maybe try the oe coils, see if theres any difference. are you on SD btw?

 

We have tried it on the oem coils and it missfires. What do you mean by SD?