I have been doing a lot of maintenance on the evo the past few weeks and recently did the spark plugs.

I didn't gap them right the first time and the car ran like garbage, but Justin at STM helped me out and I gaped them correctly (.24). Car ran better after that, but still didn't pull like it did with the old plugs.

Just to make sure I wasn't crazy I did a lot of pulls on the way to work today and the car pulled good as long as I wasn't flooring it. If I let off the throttle a little, it pulls hard threw the RPM's, but at WOT it moves, doesn't miss fire, but doesn't pull much at all.

I am confused why I could punch it and it slowly starts going, but if I let off the throttle a little then it really starts going.

old plugs are NGK iridums the laser cut ones... new ones are regular NGK's.

Ideas any of you smart guys that know these cars?

 

Could be knocking at WOT and pulling timing? Is the car tuned?

 

car is not tuned... but its all stock except a cone filter.

 

I had this happen before when I was playing around with MIVEC.

I was retarding MIVEC up top to hold boost, but found that 0* advance actually hurt power. At WOT I was in the cells with 0 advance and when lifting I was in the cells with 4.8-9.6 advance.

It was simply a difference in power yet I had the same exact feeling you describe. Almost like modulating the gas pedal above 5000rpm would provide better performance than pure WOT.

Since I was clearly tuning and playing with things, I tuned it out. Sounds to me like something similar although it's probably too much timing up top. It may also be that the higher timing just below WOT is what the car desires and you're dropping the timing too low causing power to drop off. Sounds tune related to me but it could be a small boost leak.

Have you datalogged?

 

well i haven't invested in a cable or the tuning software yet... since I have just been catching on maintenance the last owner didn't do...

 

Well since you lack the hardware to check the tune, why not do a boost leak test first and perhaps check your plug wires and gap.

Can't hurt and if the issue is still there you may want to log it. If you aren't tuning I'd have to say it's a boost leak most likely. Sometimes the stock pipes expand a bit under boost and they won't leak until it expands. You lift and they shrink just enough to fix the leak and power comes back.

Leak test it my friend

 

okay i'll see if the local shop has a boost leak tester I can use. if that checks out, I may invest in new plug wires...

should i look into coil boots also?

 

Are you sure that the car hasn't been tuned? Lots of Evos get put back to stock in a rush before being sold. The car might have been tuned, and now that it's back to stock the tune isn't right.

 

not sure on that one, but it ran excellent till I swapped the plugs.

on an other note i did find a lose clam on the UICP and after tightening, it got a little better but still a noticeable power difference between WOT and a little off WOT.

 

well swapped the plugs back, all power is back... weird.

 

What plugs are you using?

 

was trying to use just the standard cheap NGK's. the ones that i just put back in there are NGK Iridium 9's.

 

You can't use cheap plugs on the 9's, the 8 and 9 do not use the same plug.

 

Nice so the guy that sold them to me was wrong. sweet. well at least I have my power back.