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Hello,

Hoping I might be able to get an answer to a strange anomaly that happened recently.

I was driving cross the US and in Colorado/New Mexico etc higher I seemed to have to push my car really hard to pass on the highway or even climb ascending roadways.

It really felt at the time the car was gutless and I had no turbo boost<which I eventually learned was exactly what happened>.

In Texas my car threw a code which I think was something like boost control valve or whatever was malfunctioning. I reset the engine code at an Autozone and all of a sudden the car regained the extra turbo boost in always had. The code never came back again but I am now living at sea level so not sure if that has something to do with the car functioning properly.

I am just wondering if I should perhaps replace something that might have been the culprit to this happening. A Volvo mechanic mentioned the MAP sensor or something like this.

I drive a 2004 V40 wagon.

Anyone have any idea as to why this happened or perhaps what part might be on its way out? Im planning another drive and would prefer this not happen again!

Thanks!
 

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The 04' s have two map sensors, one located on the manifold and one on the intercooler outlet. The boost control solenoid would vary duty cycle to adjust pressure to the wastegate as needed based on how much throttle position was open.

The map sensors should adjust for atmospheric pressure changes, which would explain less boost, or more strain under boost when doing more mountainous driving.

As elevation increased, the less oxygenated the air was and higher the atmospheric pressure, the less increase in engine performance you would net from additional boost. As you get back down to sea level, the engine has to overcome less atmosphere and the boost is more effective in raising engine performance.

At the end of the day a 170hp 2.0L 4cyl that weighs nearly 3,000lbs under full load in the mountains is not going to pull like a train, (especially if the boost control solenoid was NOT allowing the turbo to boost what it should 7-9psi stock).

By clearing any codes you effectively reset the ECU's on board diagnostic monitors and it began to relearn fuel trims and emissions components at closer to sea level so the boost was there and never left. If you haven't, I would replace the boost control solenoid, they usually don't just throw codes unless they are failing open, which if they do, you would only see the mechanical pressure that your turbo wastegate could supply, which on a stock setup would be probably 3-4psi.

Hope this helps!

Adam

PS: I have several boost control solenoids that are known good units that i wouldn't mind throwing in an envelope and sending your way.
 
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