My wife was accelerating out of the tolls today and the car started slowing down on its own. She pulled off and shut it down, restarted and drove the rest of the way home (~35 miles). I was able to drive it a couple miles to Autozone and it was way down in power (limp mode I suppose). The code was P1688 which I'm reading is most likely either a bad bypass valve or a bum crank pulley.

I found the detroit tuned instructions on how to get to the BPV but how does one know if it's bad? Also, any tips on checking the crank pulley? I'm assuming of the two I should be hoping it's the BPV...

Oh, car is an '05 MCS with about 70k.

 

When my BPV died it would stick open. You can reach down below the inter-cooler and move the arm that connects the valve arm to the vacuum actuator. When mine got stuck I could tap the arm it would "snap" shut. Then I moved the arm and feel friction near the end of travel.

I installed a DT BPV and it fixed the problem.

Minimania has a pretty good picture of the arm at (DT shows the opposite side...):

http://new.minimania.com/web/Item/NME7609/InvDetail.cfm

-Jim

 

Thanks, so in that picture the arm is on the lower right? Which way does it move?

 

Hi Mike,

You are correct, the actuator arm is on the lower right. The black arm moves in and out.

Jim