Boost wavering... bad wastegate?

[1QuickV6]

Hey guys,

I've got my '86 back on the road and and it's breaking in nicely so far. I do have an issue that I wanted an opinion or two about...

My boost pressure "wavers" up and down under constant throttle. It seems to do that with any pressure > 10psi. Below that it is either unnoticable or nonexistant. This wavering almost feels like it's cycling up an down... there is no knock associated with the cycling, and there is no miss either. It's just a boost issue.

I've got a VDO boost gauge, a TA-49, and an adjustable wastegate (not sure if HD or not, at least 4 years old). I'm running a Jim Testa chip with 49 lb. injectors.

I have got the wastegate solenoid out of the loop (blocked off the hose that went to the solenoid so as not to bleed any air). It made no difference bypassed or not. MAF readings are solid. Turbolink shows nothing unusual.

I'm guessing either a vacuum line or a bad actuator. Any thoughts?

Thanks!
Erik

 

[Dan Thompson]

Is the boost gauage a vaccum/boost? If so at idle how much vaccum is the car drawing? I get almost 19 lbs when cold in Park.

Warm in gear its about 14-15lbs.

 

[1QuickV6]

Dan,

The gauge is boost only, but it can be swapped temporarily with a vac/boost that i've got. so you're thinking vacuum leak then?

BTW, the cam is a custom grind from Turbo People, and it's got some lope to it. To be fair, this wavering boost was present before I had the motor rebuilt (there was a stock cam in the original build). Idle is decent despite the current cam, but it will occasionally die on me once or twice when warming up at idle.

Erik

 

[wickedtt]

maybe its the gauge