Roush boosting at cruise

[martinitime]

Hi All,

Just picked up this Gen 1- 60K miles. When cruising it will surge boost anywhere from 3-10 PSI. Doesn't matter if it's cruise control or not. Also happens a tiny bit when leaving from a dead stop. Has the full Roush package and should have the stock Roush tune. Want to be sure it couldn't be anything else besides the tune. Any insight is appreciated.

 

[dsg2003mach1]

personally I'd inspect the operation of the bypass valve on the blower and associated vacuum lines. Engine vacuum opens the bypass valve so the air doesn't go through the rotor pack and into the motor. A lack of vacuum or a failed diaphragm in the bypass valve will cause it to be in boost all the time. I can't say I've really seen one be intermittent like that though

cant watch the video with sound - while Im not sure what would cause the gauge to have a false reading of going into boost it doesn't look like the truck is surging forward - do you hear blower whine or any other indicator it's actually going into boost?

 

[icecoldak]

Looks like a gauge issue or wiring---from the sound of it you are not going into any boost at all, just the gauge moving!!

 

[martinitime]

Looks like a gauge issue or wiring---from the sound of it you are not going into any boost at all, just the gauge moving!!

Unfortunately you can feel the truck pull when it surges. It is not just the gage.

 

[martinitime]

personally I'd inspect the operation of the bypass valve on the blower and associated vacuum lines. Engine vacuum opens the bypass valve so the air doesn't go through the rotor pack and into the motor. A lack of vacuum or a failed diaphragm in the bypass valve will cause it to be in boost all the time. I can't say I've really seen one be intermittent like that though

cant watch the video with sound - while Im not sure what would cause the gauge to have a false reading of going into boost it doesn't look like the truck is surging forward - do you hear blower whine or any other indicator it's actually going into boost?

When it does surge I hear sound coming from the front dash area. Best way to describe it is a hamster wheel meets a deck of cards. Only hear it for a second when the boost gage moves significantly. Feels like I blipped the throttle for a second.

 

[MTF]

Do you know if you have a "Pedal Commander" installed?

 

[Gen1TillDeath]

Yeah X2 on the bypass valve. It’s there so that you just aren’t CONSTANTLY going into boost. Sends vacuum to the solenoid keeping the valve open until certain vacuum and rpm are reached then builds pressure.

 

[Gen1TillDeath]

Do you know if you have a "Pedal Commander" installed?

This is a very good question!

 

[martinitime]

This is a very good question!

Good question but it does not. Had one on my last truck.

 

[Mako24]

Had pretty much the same issue with my whipple from when a shop installed it. Ended up taking it to JDM and they fixed everything. They tuned it but they also recommend changing out the throttle body for a Ford Racing one, which they did. Haven't had any problems since and am very happy with their work.