I just got my SS back after the MAP sensor blew out of the tube when the pipe broke.

Now in the AM yester day and today for the first 3-4 miles it builds boost then pop puts out a puff of smoke and then drops pressure.

After I drive it a few miles it is all good at 19-23 PSI.

It is like the blow off valve when cold pops off?

Anyone have this happen or have a clue?

 

Take the BOV cover off and make sure the diaphragm hasn't swallowed the spring. (vac-lock) I found mine collapsed, when experiencing weird boost issues like your stating. I replaced mine with the stonger Dejon spring ($13 shipped) and have not had any issues.


when I removed the cover, the spring was compressed by the diaphragm....so I was only getting minimal boost, etc when WOT and weird or no boost at lower RPMs. So bad, that when I pried the diaphragm off, there was a whoosh of air released! Since car was not running, this should not have been the case. Hence, vac-locked.

-J

 

But would that do it only when it is cold for the fiest 3-4 miles and then run correctly?

 

hrm...if only when cold, and only first few minutes...then maybe not. Mine was erratic in a warmer afternoon and colder morning, but consistently lower boost when not "into it" and maybe half/erratic when into it. I was expecting to find loose clamps....but instead found the diaphragm issue. I fixed mine the next day, so didn't have lots of testing in incorrect state.

 

This is a cold only problems as it runs fine when up to temp.

 

I just went for a new run with out a load in the back. [If you need to figure out how to haul a Soap Box Derby carin a HHR ask me. FYI it was our first run in our first car and we pulled a 6th in class and a Trophy on the hill in Akron].

Anyway I took a new drive and it has to be the pop off valve as it makes a pop or bang sound and losed all boost if I floor it. Now if I hit the gas and let off just a bit and then jump on it it will hit over 20 PSI cold or warm.

 

I figured out what was wrong and the dealer repaired the issue. The engine AC compressor was making contact with the map sensor in the new intake tube.

I spotted this in a GM tech web site and they recomend during installation to check the AC compressor and hoses on clearance.

IF not it will drop pressure under WOT at low speed.

 

Crazy. Good find.

 

Do you know what they did to improve the clearance issue?

I was looking at mine recently, post-kit-install, and there looked to be only a few mm's of clearance between the new sensor (specifically, the new wiring connector body, attached to the sensor) and the AC compressor itself (not hoses).

At first glance, doesn't look like anything can be "bent/tweaked" out of the way to make more clearance.

 

The tech on line said to gently bent the line away and my tech put a pad between to prevent any chance of it hitting the compressor.

I have not been under it to see what he put in.