Ok so where to start.

My wife and I have an 08 Evo GSR. We bought it used from Carmax about a year and a half ago. In the last few months we've begun to modify it and in the process have uncovered a problem or created one which I need some help with.

We've installed an AMS single exit catback, Hallman mbc, AEM wb02 and AEM boost gauge. A few weeks ago we added an AMS Performance intake and that same day had it tuned by by the local Evo guru. During the tuning process we increased boost to peak of about 24 but it usually seems to hold about 20. During this process though the car developed a hesitation that seemed to only get stronger to the point where the car would start bucking so bad you had to let out of it. That day we tried a few things to cure it. The guru has a new Ralliart so we borrowed the mafs and switched the blue relay in for my black one. Neither had any affect on the condition. That day with left with the car driveable but definitely not tuned.

Over the next few weeks we took it to a local performance shop with a good rep and they messed around with it. They had no luck the first time. The second time the tuner was there to help. In the end they suggested new plugs. We put in new plugs a few days ago and it did not help. But after the second trip to the shop the tuner did make a few changes to the afr and things seem to be a little better. It is just a hesitation now as opposed to the bucking bronco it was.

After the plugs didn't help we contacted another local Evo guy and talked to him. He suggested poking around here and seeing if someone here could help. He talked about maf recalibration files since the AMS intake seems to mess with them. At this point I'm just hoping someone has some good ideas and can point me in the right direction.

I'm a truck driver and spend a couple weeks at a time on the road. I enjoy working on cars and fixing them but I'm way behind on all the tuning stuff. And honestly I don't have the time to learn it.

Thanks for any help!

 

I had the same issue with my evo viii a long time ago....it would buck hard as hell due to fuel cut..turns out my turbo was slowly letting go. it could be something else for you though...I would look into spark plugs or anything related to that.

 

The bucking you're describing sounds to me like fuel cut. If they fattened it up and the bucking went away that would make sense. Best bet would be to see what the AFR is when it's happening.

 

its in your tune.

 

I agree, problem is the tune. As well as you are using a MBC...

 

You are probably hitting the Load Limit tables.

Check for fuel cut when it happens. i.e. IPW goes to 0

 

There's plenty of topics on this subject here so I recommend a search first.

If the bucking feels like a brick wall then its fuel cut (load limit).

If it is just a slight hesitation / pop then it is probably too rich (or bad plugs, but unlikely).

 

Thanks for the replies. Like I said it's got brand new oem plugs. So I don't think that's the problem.

After the initial tune the bucking was bad. When it went to the shop and the tuner was there he leaned it out and now it's better but still there. When we were logging pulls boost stayed consistent. The load is what fluctuated badly. Also when the load dropped/peaked/whatever it was going rich so I don't believe it's fuel cut.

This weekend I'm gonna put the stock sure box back on and see if it helps.

 

Putting the stock air box back in made the problem go away. So essentially the problem is the tune. What I need now is the maf scaling table for the AMS intake on the X. Anybody able to help with that? Please?

 

Pm meh with your tune file.

 

Ignore.... overlooked where you found it must have been related to the intake. Glad you're able to isolate what the culprit is.

 

...is a new "local Evo guru" AMS also does email tunes.