not enough boost

phum · **Posted:** Thu Dec 28, 2017 7:01 pm

Scan code tells me there is low boost.
I have removed inlet and outlet hoses, doesn't seem to be any play in compressor wheel and no oil or muck to speak of in houseing. Compressor wheel spins freely at idle with no hoses attached.
Doesn't seem to be any air leaks on pressure side.
Can any body give any pointers onwhere the problem lies?
P.

PS. 2006 crd.

flash7210 · **Posted:** Thu Dec 28, 2017 7:08 pm

MAP sensor. On top of the engine. Next to the fuel rail.

Not to be confused with MAF sensor, on the air filter lid.

WWDiesel · **Posted:** Thu Dec 28, 2017 9:13 pm

Another area to look at in addition to the MAP sensor:
Check the plastic vacuum line going from the top of turbo vane servo to the vacuum modulator located on the passenger side fender and make sure it does not have a hole or crack in the line or one of the connection hoses on each end.
Also make sure you have good vacuum feeding the turbo vacuum modulator controller. :wink:

Items 1 & 6 in the diagram:

There is also a vacuum solenoid next to the vacuum modulator that has been known to go bad and when this happens, it will not allow any vacuum to the modulator valve.
The solenoid can be safely bypassed for a test to rule it out!

There are several parts as identified in the diagram below:

#2. is a vacuum reservoir, it is a small vacuum tank to supply a backup or quick supply of vacuum to the modulator valve when called for.
#7. is a modulator valve, (big valve) it modulates vacuum to the turbo depending on input from the ECM (engine conditions)
#8. is a solenoid, (small valve) it simply is either open or closed depending on engine running or not. It tries to hold vacuum on the vacuum reservoir when the engine is shut off.

The vacuum solenoid #8 can be bypassed as well as the vacuum tank #2 for test purposes.
The modulator valve #7 should never be bypassed; if you do the turbo vanes would go to 100% all the time! :roll:

mass-hole · **Posted:** Thu Dec 28, 2017 9:21 pm

I agree on the MAP as one of the first things to check. My stock one was reading incorrectly but had not totally failed.

phum · **Posted:** Thu Dec 28, 2017 10:07 pm

MAP clean, I was surprised by the amount of crud on it considering the egr has been disabled and a provent fitted.
Checked vacuum hoses, nothing obvious there.
Now to put it back together and test drive before I go further.
Is there a way to check if the vanes in the turbo are operating correctly?

phum · **Posted:** Fri Dec 29, 2017 3:23 am

Had a test drive.
2 codes now there p0101 and p0102 MAF sensor problem and c2001 no idea what that is.
At WOT. I get a max of 17psi boost . Is this correct ? I think that I saw 30psi once before. Still clouds of black smoke and not much get up and go.
P.

flash7210 · **Posted:** Fri Dec 29, 2017 10:04 am

On a stock tune the highest boost you will see is 22 psi. And only briefly. Max sustained boost is usually 18-20 psi.

Some things you can try.
1. Bypass the small vacuum solenoid. Just run a vacuum line from the rectangular reservoir to the large solenoid.
2. Get the engine up to full operating temp and give it a few good hard runs to blow the carbon out.

not enough boost

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