I have a 2005 EVO MR
155,000 miles

Engine Mods:
K&N Intake Kit
EVO 9 Diverter Valve
AMS TBE with high flow cat

When I installed the TBE I borrowed a stand alone air/fuel meter and did some WOT runs and the A/F was dead on the money. I have never tuned or dyno the car, but it had the K&N Intake and 88,000 miles when I bought it. It came from a dealer so I had no contact with the previous owner.

I have an AEM Boost Gauge.

The car has been running fine. No issues in drive-ability and no check engine lights.

I rarely drive the car hard so I;m not really sure when this problem started.

Normally when I would go WOT the car would boost up to about 21-22psi and then would bleed off as the RPMs climbed and would settle around 17-18psi.

A few days ago I was getting on the highway and I had to accelerate to get ahead of some traffic and when I went WOT in 4th gear that car seemed to miss fire or skip or something. It was like either a cylinder was randomly missing or it was loosing boost for like a second. I tried to diagnose by going WOT from low RPMs in 4th, 5th, and 6th. The best I can tell when I go WOT and the boost goes above 20 the car kind of skips a beat. Once the boost falls to 18-19 it pulls hard and has no issues. Same thing in all the gears. Sometimes it will hit 21-22 with no issue, but 90% of the time it has that little skip when above 20psi.

Has anyone had a similar issue?

I'm planning to do an oil change next week and can check the plugs and do a compression check, but I don't have a boost leak tester.

Any thoughts?

Thanks in advance for any help.

 

Bump.


I was originally worried that the clutch may be failing as it has at leat 80K miles on it and I am unsure if it is stock or aftermarket. From what I have read though there is a massive jump in RPM with a loss of power at the same times, and my car does not do that.

 

Get fresh spark plugs and gap them to .020", report back with results. Your issue sounds like spark blow out. Could be just plugs, could be weak coils.

 

Thanks! I'll give that a check. Are there any visible signs of spark plug blow out to look for?

 

No, spark blow out is basically a misfire that only happens at WOT, so you're not going to see unburned fuel because it's not constant. But you'll know when it's fixed. But stop going WOT until you've started the repair path because if it misses bad enough you lift the head.

 

Update:

Pulled all the plugs. They were all beyond .28 which was the largest feeler gage I had. Ingot them all down to .22 and the car run much better and very strong. WOT pull in 6th gear and it held 20 psi and pulled hard.


Thanks!

How do I give thanks to people so it is recorded?

 

Click the thank you button in the lower right corner of my post