Sometime ago I got a CEL for "mis fire" on all cylinders on the right side.

I spent months trying to trouble shoot it, includings lots of advice on this board, and finally paid my local mechanic $1k to determine it was the Hydraulic Valve for the Variocam - p/n 996-105-301-72 (this is a supereceeding p/n), located between the spark plugs (also on that side).

I posted the result and then several of you came out indicating it was a common problem (now you tell me) and that the cracking of the bracket that holds the valve in place was typically the root cause.

Recently I had the same fault on the left side and sure enough, it was a broken bracket p/n 996-105-310-72. The CEL fault was very intermittent this time and when I got in there, the bracket, cracked on one side seemed to allow the valve just partially out of its cavity, thus probably functioned most of the time.

This time I thought I'd share the fix and the improvement I devised in case some of you hadn't experienced the problem yet.

The fix / improvement involves replacing the brackets on both sides with new parts that have had their sharp edges polished to eliminate the sharp, die cut corner breaks that are the source of stress concentration and thus fatigue cracking, and also, the addition of a back-up, or doubler plate added to the weaker of the two bracket legs (made from the brackets I removed / replaced).

You'll see several pictures that show a) the broken bracket as found in the car b) a New Bracket, note that one leg is contoured and thus much weaker, and c) the Cracked Bracket with the New Bracket. Note polished edges in crack area on the new bracket and that the crack is in high stress area on weaker bracket leg, and d) the back-up doubler plate made from the old bracket (sawed off of the broken bracket and filed to match contour). d) The new bracket with doubler plate installed.

Hope this helps.

 

That bracket ended up fixing my misfires as well. Nice post.