Need help, car shakes oddly at 17psi or higher?

[bob123131]

So car ran fine at 20 pounds for like 2 months blew a coupler off and when i put it back on the car wont take anything over 17? I have searched, but with no luck, the car isnt over boosting like if the wastegate was stuck or the opposite blowing open. It's just once it hits 16 or 17 it starts bouncing back and fourth through a couple psi and there is no power. I have a dual stage and going from 10 to 20 there is no power change. All my mounts are fine i assume my wastegate is fine too because it worked fine before the coupler fell off. No boost leaks. Checked plugs and they all look fine one had a bit of oil in the galley which i cleaned out and no change? Any ideas on what i might be overlooking or something i should defintly double check i have a dyno tune in two days?

Not sure if this could have helped lead to premature failure, but i added two washers to my wastegate actuautor mount on my evo 3 with the flapper mod about a month ago, but everything has been fine since?

Also tried turning off my second stage on the bc and just raising the first to see if it was an internal spring issue or something, but didnt help

Its like compression surge but i didnt change the bov at all or anything since it worked fine.

 

[habitatguy187]

Either a boost leak or a misfire. Could be anything in the ignition system, plugs, wires, coil packs, power transistors, I'd double check for boost leaks then start with plugs, move on to wires ect. If the new expensive wires don't fix it then just take them back.

Problems like this are usually fixed easily, but sometimes take awhile to track down, might want to cancel your dyno "date".

 

[bob123131]

No boost leaks, wires are fine tried to ptu's and coil packs.

 

[slowgsr]

you might have overspun the turbo when you blew off your coupler. Check for shaft play.