Boost is surging!?!?

[Blayne]

Ok, I changed my head gasket the other day, and all went well. I had a sensor that wasnt plugged in, but I got it all done now.
My current problem is that I am getting what seems like boost surge. What happens is when I get on the throttle hard, the boost goes up to like 16 lbs. (not 100% on the exact # cause my gauge is in bars) and then comes down to like 10psi and back to about 15 and then 11 and then 14 and 12.....you get the idea. After about 5 seconds in the boost the psi seems to level off. I don't know if this is a prob with the turbo, or fuel. I don't hit fuel cut either!!
I will give a list of my mods to help with the diagnosis.
-16g EVOIII.....3 months old
-new fuel filter changed at the same time as the head gasket
-3" exhaust after the cat back
-greddy hard piping
-greddy type s BOV
-HKS mbc which I just put on last night...and when the surging started!!!

I think that is all that would have an effect on this problem.
I still have the stock fuel system and injectors.
Could it be the MBC that I just put on? I got it used but I cant see it doing that. I really want to fix this problem so the car will be running properly for the first time since I have had it!!

Thanks

 

[Spoolin98]

Fuel has nothing to do with boost issues.
Sounds to me like you have a bad MBC or you installed it wrong. Try bypassing the MBC, go from your boost source right to the wastegate, if your boost problem is fixed, then the MBC is your problem.

 

[Blayne]

Thanks, I will try that!!

 

[ddavisaf]

I'd recommend also running a Boost Leak Test.

 

[MyBeatGSX]

Yea that boost controller sounds like its crap. If that isn't the case, can you be more specific about what RPM and throttle positions it does it at? Mine did the same thing at part throttle and it turned out to be compressor surge.

 

[Blayne]

I connected the turbo right to the wastegate and it went away, so it is the MBC. I will go get a new one today. I bought this one from a member from another board. It is an HKS and is a few years old, but I didn't think they could actually go bad. I guess so.
Thanks guys!!!

 

[Spoolin98]

I connected the turbo right to the wastegate and it went away, so it is the MBC. I will go get a new one today. I bought this one from a member from another board. It is an HKS and is a few years old, but I didn't think they could actually go bad. I guess so.
Thanks guys!!!

Are you sure you don't have it hooked up backwards? They tend to act funny when you do. Glad to see you found the problem.