Tech Tip: BOV Troubleshooting


If you have installed a vent-to-atmosphere BOV and your engine is started to dip below normal idle and stalling, do the following:

• Check that the BOV is closed at idle. If the BOV is not closed at idle, the spring tension needs to be increased or the BOV might need a heavy duty spring.

• Check the vacuum hose for splits, cracks, loose connection, kinking or any obstruction – old or fatigued hose may collapse under vacuum causing an obstruction

• With the engine running remove the vacuum/pressure hose from the nipple in the cap of the BOV, there should a loud hissing sound. The engine should idle poorly, double check by covering the end of the hose with your finger. If this does not occur, the hose could be blocked or crimped. Check the hose and replace if necessary.

If the stalling dipping idle is still occurring do the following:

• Ensure that the vacuum/pressure source is not shared and that the vacuum source is directly from the inlet manifold?

• Check the seal between the adapter and the BOV – ensure that there is no gap between the BOV base and the weld flange?

• Check the join between the adapter and the intercooler pipe for leaking .

Note: Some cars with sensitive Air Flow Meters will not respond well to atmospheric Blow-Off Valve. Turbosmart recommends fitting a bypass-type BOV like the Plumb Back. Fitting a bypass-type BOV will eliminate the stalling problem.


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