Originally Posted by emerydc8

This came from Jim Forgione's web site. Could your O2 sensor be shot? Jim does refer the reader to a link that discusses contamination of the MAF due to use of the silicone product your mentioned and it could cause the engine to go rich, like you described. K6JRF Auto Page

K6JRF Auto Page
Warning . . .
I was sent a interesting note from another 140 owner who came across the warning from Berryman Products on the use of 'silicone' under your hood. Here's what they say; Silicone of any variety will contaminate the oxygen sensor. And the amount of silicone needed to do this is minuscule. How minuscule you may ask? A well known example is: Silicone-based RTV gasket sealants. These type of sealers outgas small amounts of silicone when they cure. If you use one of these sealers on an oil pan or valve cover gasket, the silicone vapor will be sucked into the crankcase ventilation system and then into the intake manifold. As a result, the oxygen sensor, once contaminated with Silicone will be inoperative within a day or two. Likewise, do not use Silicone-based lubricants anywhere under the hood, or anywhere forward of the firewall.