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Old 02-04-2011, 08:57 AM
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Robyn Robyn is offline
Missy Good Wench ( Moderator)
Join Date: Apr 2001
Location: Newberg Oregon
Posts: 9,901

You can try swapping out the MAP sensor. (little rectangle plastic box on top of the intake plenum)

The Barometric sensor (firewall slightly to the passenger side fo the hydro boost) can also cause issues.

These two sensors feed info on whats going on with air pressure inside and outside the engine and if faulty can make a huge difference in the way things work.

With 15" at idle then near zero when running means that the ECM is pulling the vacuum off way too soon.

The last one of these I had an issue with, I replaced the chip with a Heath Chip (vacuum system overide programming) plus I installed the turbo master.

End of issue.

Just be sure to have gauges (Pyro and boost) and drive the thing accordingly not exceeding 900F Post turbo or 1000-1100F preturbo

Keep the boost set no higher than 12 PSI .

This works fine and then you can stop chasing the gremlin.

The vacuum system was a good idea, but the application hardware and software were a tad unreliable.

If you are not getting any codes (78) for wastegate solenoid then there is another issue.

With the solenoid bypassed, you should see more than 6 PSI of boost under a hard pull.

Was the vacuum reading on the pump steady at 20" ?? if the needle wiggles it means the pump is shot.

The last several pumps I have checked, all ran 26" at the pump.

I agree on the 15" being minimum, but 20" is not uncommon.

What do you get for vacuum at the Turbo if you just rev the engine ?? it should not change much, should be near 15-20" HG

Keep us posted

(1) 95 Suburban 2500 4x4
(1) 2007 Chevy Avalanche
(1) 1997 Astro
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