I getting frustrated w/ what I think is a vacuum leak at my intake manifold. Pretty much all other possibilities have been eliminated.

It's especially frustrating because I've converted to propane, have a feedback computer and cannot get it dialed in.

Problems:

Occasional missing, coming from cylinder #6. Electrical problems have been eliminated.

No matter what, the 02 sensor I've got installed in the exhaust reads lean. Still, the propane mixer (replaces carb) is adjusted as richly as possible and there is the smell of propane in the air, which I assume means running rich.

Manifold has been planed at a machine shop.

No apparent exhaust leaks.

Can't find anything with the WD-40 method

any suggestions? New manifold gasket?

Thanks,

Joe

_________________
Joe Hoppe

71 D100 225 Super Six 727 AT on 2008 Crown Vic CopCar frame

64 Valiant Wagon 225 904 AT 3:23 8.75"

Plugged exhaust, bad lobe on cylinder 6, or the mixer can't flow enough propane? Are the other cylinders running just fine, but overall it is running lean? I'm wondering if the O2 sensor isn't working properly in that case, I've heard recently of an issue where the exhaust wasn't grounded properly, causing an improbably O2 sensor reading.

Where does the vaccum line for the brake booster go? I wonder if one of your vaccum accessories is leaking (line or accessory).

Lines are all good. Pretty sure exhaust is not plugged. Bad lobe on the cam seems extreme, but I don't know for sure that that isn't the problem. I have adjusted the valves recently, though, and there was nothing obvious there. Lines have been replaced and are in good shape.

I'll look into the sensor being grounded.

Thanks,

Joe

_________________
Joe Hoppe

71 D100 225 Super Six 727 AT on 2008 Crown Vic CopCar frame

64 Valiant Wagon 225 904 AT 3:23 8.75"