I have a 2008 Evo X. I had it tuned in fall of 2009 and have never had trouble with it. This past week, the car has felt slow, sorta like it did before I had the tune. The car has very uneven acceleration and it doesn't throw me back in my seat like normal. Today I was on the highway and I dropped it into third to test WOT conditions. I floored it going about 50 MPH, and the car bucked violently and then the Service Required message came on the dash, and the ASC OFF light is on. I did a search, and some people are saying overboost?

If it's overboosting, why would it start now, 2.5 years after the tune? The only thing different about the car is I took the rear speakers out a few days ago to replace them, but I don't see how this could affect the engine.

Mods: Magnaflow CBE, WORKS air filter, custom dyno tune

Any ideas? Thanks guys

*UPDATE* FIXED!! It turned out to be a faulty fuel pump relay. Thanks to speedytl for suggesting I swap out the high beam relay for testing. The new relay was under $20!

 

No idea why the ASC would go out, but engine problems after WOT always call for a boost-leak check.

 

Hmm. That's sort of what it feels like. That would explain the uneven acceleration...

I've checked the fluids by the way. The CEL is gone after turning the car off and back on, but it's still driving terribly.

 

Boost leak, plugs, MAP or MAF sensor. You might put a code reader on it and see what, if any, codes you are getting.

 

How can I test for these problems? I really don't want to take it to the dealership and have them flash over my tune lol.

 

If you have a boost leak that big and sudden, there's probably a hose blown off somewhere. Do a good visual inspection of all the vacuum/boost lines, intercooler piping connections, etc.

 

More than likely its a boost leak. Make sure you do a VERY GOOD visual check. Alot of times problems like this are often thought to be alot worst than they really are. Take your time when you do it. Hopefully you find a loose hose somewhere, goodluck.

 

Thanks, gonna get in there with a light right now, I'll post what I find

 

First thing id check is spark plugs gaps.

 

I just went over it with a fine toothed comb and I don't see any hose issues. Everything is super tight. What do you mean by spark plug gaps? I'm clueless with this stuff, sorry. I mean I know what a spark plug gap is, but are you saying they could be damaged or something?

 

Do you have CEL. My friend had a similar issue while at an autocross. Apparently the MAF went bad all the sudden. If that's the problem buy it at Autozone and save some money.

 

A MAF-oriented CEL on a car that autocrosses makes me ask this question: did the owner add a drop-in K&N and over-oil it?

 

+1. could be the MAF, especially if your idling high. See if someone can pull the CEL code for you to confirm.

If you need to replace the MAF try to get one from a salvage yard. They are the same part used in alot of late model Mitsus. I have been through 3 so far (damned HKS drop in filter ) and this saved me over $50 each time.

 

The CEL is gone right now.

I know this sounds dumb, but would these symptoms be caused by accidentally putting in 87 octane? Last time I filled up I was doing 10 things at once and I'm starting to wonder if I put in 87 by accident.

I think this would make sense because it's fine as long as I don't go WOT.

 

Yes. 87 is bad. It probably wouldnt stutter though but could hurt the motor. Check your receipt. first get good gas in the car.

The cel light is gone but the code is stored. Get a code reader and see what it says. Auto zone has them to borrow I think.

Evo x plugs are iridium and don't get tapped. They could be bad, but gap isn't it.

No way to check you MAF sensor, replace it and see if you are fixed.