I recently replaced my entire PCV system (oil return hose was broken). Car has now never run better. Seems like a new engine almost - amazing difference. Wish I had caught the problem earlier. But the car has since failed the CO 1.10 limit reading 1.58; and the NOX 3600 limit, reading 5600 emissions. HC is within limits.

Previously, the car had been pushing oil up into the intake manifold and it got pretty blackened up in there. The oil pan looked crummy and I'd like to clean up the inside of the intake manifold and the engine. A friend Volvo tech suggested I put in some ATF with my oil and run it like that for awhile. My question to the board is for an opinion on how much ATF - 1 quart or a half quart?

I'm also running the CRC Guaranteed to Pass Emission Test Formula (can't hurt), thru the fuel system, and then draining the oil, right after using some gunk motor flush. I'm replacing a few other parts also.

I'm thinking that perhaps the two years of driving with the failed PCV system might have left some residual crap in the engine and intake manifold and it needs to be cleaned. When the cleaning is finished I'm going to have the CAT tested. It has a lousy Bosal CAT (won't buy one of these again). I hear the after-market CATS only last for one or two years? So, if it fails the CAT test then I will get a new CAT ... in the meantime ...

Btw, we have a 740 and it had a Bosal CAT and all the cleaning and adjusting did not mean jack, it needed a new CAT (failed CO and NOX). But I suppose I have do at least try to do all I can, just in case it ain't the CAT.

thanks for opinions
diyer