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high boost

STEVE53

STEVE53

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Location
wasilla, ak
I have been experiencing high boost lately. On the highway going ~65mph, it is around 6-7psi. At 75mph, I was watching my gauge and while climbing a slight hill, boost got around 16psi. I got off the pedal enough to not code. My boost on the highway on flat ground used to be 2-4psi. I have no computer mods at all. I am thinking that I have a bad sensor or a bad boost solenoid. Any ideas or similar experiences/solutuons would be appreciated before I blow a head gasket.

Steve
 
If it's any comfort to you at all, mine is set to max out around 15-16 psi and when I'm towing heavy, I'll hit it regularly on long grades. Keep an eye on EGTs, but I don't get concerned since mine always stay pretty low. I can't speak to the issue on the bad sensor, but just wanted to offer a level of comfort that the pressure seeing isn't harmful, to my knowledge.
 
12psi is about the max you want to run with stock turbo assuming the engine is all stock, after that the exhaust back pressure becomes real high and adds stress to the motor.

I would think you have a bad waste gate solenoid, sounds like it's sticking open and not closing when it should. You can try spraying some wd40 in the openings to free the ball inside. If that doesn't work, try replacing the waste gate solenoid.

No codes or check engine light?
 
1st thing I would do is check your boost gauge to make sure it is correct. If it is fine, then a scanner is next to check the turbo boost pressure sensor readings. If it is reading correct then your barometric pressure sensor(the one on the firewall) could be bad. If the boost was jumping and all over the place I would suspect a bad wastegate solenoid, but if it is holding steady boost(just to high), I would suspect a problem with a sensor for the control side.
 
WG locked up? Engine off see if you can move it - you may need to remove the vacuum line to the turbo at the turbo. It only needs to move 1/4" or less.
 
I checked wg solenoid and it is free. I thought that maybe the gauge was going bad, but the first time that this happened, it did code and go to limp mode. The boost gauge moves smoothly, so I suspect that there is nothing stuck. I was thinking a sensor due to the gauge not bouncing around, like the computer thinks there is less boost than there actually is.
 
If it coded then chances are your vacuum solenoid for the wastegate has stuck on sending vacuum all the time to the wastegate(basically wiring it shut). There is a filter i nthe solenoid, and over time the foam breaks loose and takes out the solenoid.
 
I just replaced the vac solenoid and it appears to have fixed the problem. I haven't had it on the highway yet, but when I hammer the throttle around town, boost peaks around 8psi, where before it peaked around 12. Thanks for the help.
 
Update:

I drove on the highway today and boost is still on the high side. Cruise set at 70mph, boost is between 6-8psi. When I hammer it, it goes as high as 14 momentarily then hovers around 12 psi. Any other ideas what could be wrong here? I wonder if the MAP sensor could be bad giving the computer incorect actual boost info.
 
Well I removed both the MAP sensor from the intake and the baro sensor from the firewall and sprayed them both with brakleen. This seemed to have resolved the issue as my cruise boost at 70mph is back down to 3-4psi which is where it has been previously. I will eventually replace the MAP, but it is working good for now.

Steve
 
STEVE53 said:
Update:

I drove on the highway today and boost is still on the high side. Cruise set at 70mph, boost is between 6-8psi. When I hammer it, it goes as high as 14 momentarily then hovers around 12 psi. Any other ideas what could be wrong here? I wonder if the MAP sensor could be bad giving the computer incorect actual boost info.
Click to expand...

These settings are about where mine is at. Stock GM4 turbo with manual wg controller and resistor in the MAP sensor harness as to not code.
 
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