Compression question.

[Thaddeus]

I have been having issues with my newly turbo'ed KA-T.

First, at idle my vacuum is about 10 PSI or .69 hkPa, half of what is normal.

Second, when getting into boost, around 2 to 3 PSI the car starts sputtering and there is a noise like the the engine is blowing off the boost like a fart but not too loud and the car stops accelerating.

Third, when I'm just cruising down the road and I let off the gas a little and go back on it the engine surges then bucks a little.

I checked for a vacuum leak by spraying some starter fluid around the intake manifold and there was no rise in RPM or any change in idle.

I checked for compression, engine plenty warm, fuel and spark disabled and throttle wide open. I reached 152 to 155 PSI on all cylinders within 5 or 6 seconds of turning the engine. Is that good?

I am frustrated and running out of ideas.... Any thoughts,

[TheOne]

checked for boost leaks around the intercooler/piping?

[blacksrjdm]

You have...

A boost leak in your intercooler piping. Or the BOV isnt tight...

[Thaddeus]

I really wanted to try and fix the low vacuum problem first, do you think that a leak in the intercooler piping would affect low vacuum at idle.

I plugged up the BOV vacuum to see if it made a difference but it didn't, I think Neverlift made that suggestion on a different post.

My biggest concern is the low vacuum, which led me to compression after not being able to find a noticeable leak with starter fluid.

A vacuum leak at idle is a boost leak on acceleration so thats my focus for now. I am wondering if a head gasket can leak vacuum without it appearing on a compression test.

Also the EGR is blocked off and removed and the PCV is plugged and now ran through a catch can. I have tested it with these other vacuum sources plugged as well with no difference. I have also taken off and cleaned the IACV.

I'm stumped, where the f*** is the vacuum?

the only things hooked up to vacuum are the FPR, turbo timer, internal wastegate, BOV, MAP sensor solenoid and the catch can. All others are plugged. (and of course the brake booster)

Correct me if I'm wrong but the intake manifold only has the three vacuum ports at the lower rear of the bottom part and the larger port for the brake booster. But again if I was missing one it would show when I spay starter fluid around.

Help!

any suggestions welcome

[OutToWinPAHC]

smoke machine or a boost leak checker.

[Thaddeus]

Well I don't have a smoke machine or a boost leak checker so I put on the original piping on bypassing the intercooler and making it super easy to check the couplers. I still only have 10 PSI vacuum and no noticeable leaking.

There is definitely a loss of vacuum from the throttle body to the engine.

Any other ideas, at this point I"ll try them all.

[OutToWinPAHC]

Brake booster, any hissing near there at all?

[Thaddeus]

Nope, I sprayed that with started fluid too, nothing there.

What does the air regulator do, I see a lot about it affecting high idle RPM's mostly. I know, I'm grasping for straws now.