How I solved my low boost with knock issue

[Boostian]

This is primarily for future searches:

I had a problem since I bought my car with only being able to get 12 to 12.5 psi out of it without knock. Plugs were good, wires good, fuel pressure was spot on at 43 vac off and rose +1/+1 with the boost. The aftermarket gauge was still reading 12 to 12.5 psi at best. Attempts to raise it to 14 were met with almost 3* so it was immediately backed down.

Brought it to a local Buick guru last night. In popping the hood he immediately found he culprit. My vacuum line that attaches to the stock boost sending unit and the T where the gauge was plumbed in was completely dry rotted and hanging off. Replaced the hoses on the spot, backed the rod down, test drive showed 13psi. Upped the rod to where it was before and i'm sitting at 16psi with no issues.

Because I saw knock and immediately let off I saved my engine from problems. I was probably boosting somewhere in the 18-19 psi range when I attempted to mess with it before, but my aftermarket gauge was reading wrong because of the conditions of the hose.

 

[BARRACUDA1968]

Nice find! Good thing it turned out like this instead of an engine problem.

 

[GNVenom]

If that hose doesn't make a tight connection, you could see boost in the 25-30PSI range. With cracks and leaks on the "Y" hose, boost would be in a runaway state at WOT.

 

[john keskes]

Thanks for sharing! ​