No boost?

npkdm · **Joined:** Wed Sep 03, 2014 8:28 pm **Posts:** 163

P0299 code came up and it lost power. I have no acceleration. I replaced the intercooler inlet hose and MAP sensor. The outlet hose looks and feels brand new so i didn't replace it. There is no boost 95% of the time. Then all of a sudden it will run great until i shut it off. Then no boost again. what should i check next? It just seems it must be electrical the way it all comes back at once and leaves the same way.

flash7210 · **Posted:** Thu Oct 06, 2016 9:00 pm

Here are some easy tests:

1. Behind the air filter box are two vacuum solenoids, a big one and a small one. With the engine running, is the big one buzzing loudly? If so, it should be replaced and replace the little air filter that is connected to it.

2. There is a vacuum line that goes to an actuator on top of the turbo. While running at idle, pull the vacuum line off the turbo. Do you feel strong vacuum at that line? If so, vacuum system should be good.

3. Reconnect that vacuum line to the turbo. Now, look down between the turbo and engine (engine still running). You should see a rod connecting the vacuum actuator to a lever on the turbo. Pull off that vacuum line again and watch that rod drop. Reconnect the vacuum line and watch that rod pull up. Does it look like lever is getting full movement? If not, the vanes in the turbo are stuck and need to be cleaned.

GordnadoCRD · **Posted:** Thu Oct 06, 2016 9:12 pm

WWDiesel wrote:

It should reset itself and no more limp mode if you have corrected all boost leaks! Is it still bellowing lots of black smoke when you try and accelerate? If it is, then you still have a major boost leak somewhere or have a turbo or turbo vane control problem.... :wink:

My mind kind of went back to this. Can we assume you have pulled the turbo intake hose and checked for shaft play?
I have caught turbos that spin free, then bind, then spin free again before the bushings failed catastrophically. The way gyroscopic forces apply to turbines can make them hard to diagnose before outright failure.

npkdm · **Joined:** Wed Sep 03, 2014 8:28 pm **Posts:** 163

flash7210 wrote:

Here are some easy tests:

1. Behind the air filter box are two vacuum solenoids, a big one and a small one. With the engine running, is the big one buzzing loudly? If so, it should be replaced and replace the little air filter that is connected to it.

2. There is a vacuum line that goes to an actuator on top of the turbo. While running at idle, pull the vacuum line off the turbo. Do you feel strong vacuum at that line? If so, vacuum system should be good.

3. Reconnect that vacuum line to the turbo. Now, look down between the turbo and engine (engine still running). You should see a rod connecting the vacuum actuator to a lever on the turbo. Pull off that vacuum line again and watch that rod drop. Reconnect the vacuum line and watch that rod pull up. Does it look like lever is getting full movement? If not, the vanes in the turbo are stuck and need to be cleaned.

i'll try it tomorrow. the way the boost returns and leaves again makes me think it isn't a vacuum line.

npkdm · **Joined:** Wed Sep 03, 2014 8:28 pm **Posts:** 163

GordnadoCRD wrote:

WWDiesel wrote:

It should reset itself and no more limp mode if you have corrected all boost leaks! Is it still bellowing lots of black smoke when you try and accelerate? If it is, then you still have a major boost leak somewhere or have a turbo or turbo vane control problem.... :wink:

My mind kind of went back to this. Can we assume you have pulled the turbo intake hose and checked for shaft play?
I have caught turbos that spin free, then bind, then spin free again before the bushings failed catastrophically. The way gyroscopic forces apply to turbines can make them hard to diagnose before outright failure.

No i didn't check the shaft. i guess i'll do that tomorrow too. I really hope you are wrong though.....

WWDiesel · **Posted:** Thu Oct 06, 2016 11:12 pm

The veritable vanes in the turbo are vacuum actuated; the vacuum operating the vanes is controlled by the on board engine management computer via an electrical solenoid that sets over on the passenger side of the engine compartment right next to the transmission control computer.
Two possibility come to mind:
1. Turbo vacuum control solenoid is going bad or sticking sometimes causing low boost, and then sometimes it does not stick and boost is normal. (Replace solenoid)
2. Turbo vanes sticking sometimes not opening up and supplying any boost. Some PB Blaster and a little manual (by hand) exercise can cure this if that is the problem!

Either one of the above items could come and go and not be consistence....

npkdm · **Joined:** Wed Sep 03, 2014 8:28 pm **Posts:** 163

flash7210 wrote:

Here are some easy tests:

1. Behind the air filter box are two vacuum solenoids, a big one and a small one. With the engine running, is the big one buzzing loudly? If so, it should be replaced and replace the little air filter that is connected to it.

2. There is a vacuum line that goes to an actuator on top of the turbo. While running at idle, pull the vacuum line off the turbo. Do you feel strong vacuum at that line? If so, vacuum system should be good.

3. Reconnect that vacuum line to the turbo. Now, look down between the turbo and engine (engine still running). You should see a rod connecting the vacuum actuator to a lever on the turbo. Pull off that vacuum line again and watch that rod drop. Reconnect the vacuum line and watch that rod pull up. Does it look like lever is getting full movement? If not, the vanes in the turbo are stuck and need to be cleaned.

#2 - there is no vacuum at the line when pulled from the turbo. i removed it from the solenoid and there isn't any vac there either. there isn't any vac on either hole on the solenoid. is it the soleniod or whatever supplies the vac?

npkdm · **Joined:** Wed Sep 03, 2014 8:28 pm **Posts:** 163

i pulled vac lines until i found vacuum. there is vacuum before the little solenoid. so i am guessing the little one needs replaced. i hooked the line that had suction to the big solenoid and it gave me boost, but the solenoid made noise. i shut it off and the big solenoid continued to made noise until it ran out of vacuum. so im guessing i should replace both?

flash7210 · **Posted:** Fri Oct 07, 2016 7:05 pm

Yes. Replace both.
Although you can safely run with the small one bypassed

npkdm · **Joined:** Wed Sep 03, 2014 8:28 pm **Posts:** 163

Thank you so much for the help

Sent from my iPhone using Tapatalk

undrgnd · **Joined:** Sat Mar 26, 2016 4:47 am **Posts:** 194

flash7210 wrote:

Here are some easy tests:

1. Behind the air filter box are two vacuum solenoids, a big one and a small one. With the engine running, is the big one buzzing loudly? If so, it should be replaced and replace the little air filter that is connected to it.

2. There is a vacuum line that goes to an actuator on top of the turbo. While running at idle, pull the vacuum line off the turbo. Do you feel strong vacuum at that line? If so, vacuum system should be good.

3. Reconnect that vacuum line to the turbo. Now, look down between the turbo and engine (engine still running). You should see a rod connecting the vacuum actuator to a lever on the turbo. Pull off that vacuum line again and watch that rod drop. Reconnect the vacuum line and watch that rod pull up. Does it look like lever is getting full movement? If not, the vanes in the turbo are stuck and need to be cleaned.

Hey Flash,

Define loudly. I can hear my big one buzz with the hood open standing directly in front of the car with the engine running...if I can hear that is it time for replacement??

Cheers

Chris

flash7210 · **Posted:** Fri Oct 14, 2016 11:50 am

I'd say yes. It certainly wouldn't hurt.

undrgnd · **Joined:** Sat Mar 26, 2016 4:47 am **Posts:** 194

flash7210 wrote:

I'd say yes. It certainly wouldn't hurt.

Thanks mate.

logmore · **Joined:** Fri Sep 09, 2016 10:51 pm **Posts:** 4

I just ran into the same problem, Although in the process of trouble shooting, i also found my turbo had lateral play so it got replaced.

Turns out the original problem I had was the Small Vacuum solenoid, by passed it and voila i got my boost back.

Question. It is said you can run safely with this bypassed. I will have to order it , can someone define safely for me lol

flash7210 · **Posted:** Sat Oct 15, 2016 6:34 pm

logmore wrote:

I just ran into the same problem, Although in the process of trouble shooting, i also found my turbo had lateral play so it got replaced.

Turns out the original problem I had was the Small Vacuum solenoid, by passed it and voila i got my boost back.

Question. It is said you can run safely with this bypassed. I will have to order it , can someone define safely for me lol

The small solenoid is just a open-close switch for the vacuum reservoir.
Bypassing it means it will take a second to build vacuum.

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