Codes P0171 and P0174

[Jamesp]

Pumped down everything south of the vacuum check valve by connecting a vacuum source (the Extreme Super Smoker in reverse - turning out to be handy) to the check valve itself and pulling a vacuum. pulled the check valve off after about 30 seconds and there was plenty of vacuum. Checked the actuator for the butterfly valve in the resonance tube and it's tight. Can the air injection cut off valve have a constant leak that shows up in a smoke test??? I blew into the tube and that valve is closed at present. Can the butterfly valve stem have a leak?

[JFP in PA]

Originally Posted by Jamesp

Pumped down everything south of the vacuum check valve by connecting a vacuum source (the Extreme Super Smoker in reverse - turning out to be handy) to the check valve itself and pulling a vacuum. pulled the check valve off after about 30 seconds and there was plenty of vacuum. Checked the actuator for the butterfly valve in the resonance tube and it's tight. Can the air injection cut off valve have a constant leak that shows up in a smoke test??? I blew into the tube and that valve is closed at present. Can the butterfly valve stem have a leak?

Yes to both questions.

Rather than pull a vacuum and then listen to see if any is left, you need to be testing with a unit that allows you to pull a known level of vacuum and watch for any changes:



Sometimes the vacuum leaks that cause these codes are slow but continuous ones.....

[Jamesp]

Thanks for your reply JFP. I used time instead of a gauge. If the system holds a low vacuum for a full 30 seconds my sense is any leak is less than a pinhole. I think I'll go check it for a full minute though. I did listen for a hiss as well and did not hear one. I bought a plastic vacuum pump similar to the one you show to bleed the clutch as it was marketed for use in brake jobs. It would have been a better tool if it was compatible with brake fluid.

[JFP in PA]

Originally Posted by Jamesp

Thanks for your reply JFP. I used time instead of a gauge. If the system holds a low vacuum for a full 30 seconds my sense is any leak is less than a pinhole. I think I'll go check it for a full minute though. I did listen for a hiss as well and did not hear one. I bought a plastic vacuum pump similar to the one you show to bleed the clutch as it was marketed for use in brake jobs. It would have been a better tool if it was compatible with brake fluid.

I don't care for vacuum brake bleeding tools at all, I prefer the pressure style like the Motive system because it pushes clean fluid downward and through the system without any chance of pulling air in, which a vacuum system can quickly do.

[Jamesp]

Originally Posted by JFP in PA

I don't care for vacuum brake bleeding tools at all, I prefer the pressure style like the Motive system because it pushes clean fluid downward and through the system without any chance of pulling air in, which a vacuum system can quickly do.

I'll pick up a pressure system next time I'm messing with the hydraulic system. Put everything back together and working on getting through a driving cycle. I think it was a poor seal between a rubber seal and a plastic tube on the manifold. A rookie mistake, but I have an excuse. With luck, it's good to go.