During the 4 years I have been visitng this board I have read many, many posts concerning the infamous engine knock. My 5.4L S'crew does not have this problem, but my 4.6L engine that I have in my Grand Marquis does have the problem - bad. Many of you have this same engine in your Screws.

Over the years I have tried everything. Took it twice to the dealer under warranty. They upgraded the computer software which fixed it for about a month then it went haywaire again. The second time they just gave up. I have tried checking for vacuum leaks, cleaning and replacing the mass airflow sensor, etc, etc, etc. Neither Ford nor an independant mechanic could ever get to the root of the problem. The problem got to be especially bad after the car had warmed up for 20 minutes or so.

Well, it seems like the problem finally got fixed last week. The engine, which is 6 years old now, started dying immediatey when the foot was taken off the gas. I had to partially tape open the throttle so I could drive it to the dealer and not have to call a tow truck. On the way to the dealership (which was a 30 minute drive) the car ran like a dream. It was like the friggin' thing was brand new. Unbelievable.

At the dealership they put a new idle control valve on. This was last week. We took the old bus out for a roadtrip over the weekend and the car is continuing to run like new. Amazing. Apparently that stupid valve was somehow causing the engine to knock badly for the past 3 and a half years when the engine got hot. The funny thing is we never had the slightest trouble with the idle until one day when it suddenly just went totally kaput.

Anyway, just passing on my experience for what it is worth. Hope this helps somebody.