I have an 83 300D turbo diesel 230,000m in Florida.

For years it has intermittenly (months) CLUNKED on downshift, failed to turn off for 12 seconds in cold weather etc... My mechanic was clueless and I finally figured out it was the vacuum. So I fixed the hoses and everything was sweet.

Next half of story:

Since I've owned the car it has idled roughly only when the engine is well warmed up , AC on and in gear. The whole front end shakes. I've finally had enough and in the last 3 months had:

-motor mounts, dampers and engine shocks replaced
-valves adjusted
-injectors replaced
-engine damper screw replaced and adjusted

$800 later the bastard still shakes. To add insult to injury, the first thing listed was just done by my mechanic and now the vacuum problem has come up again.

Qs:

1. What have I/my mechanic missed that may be causing the rough idle problem?

2. All my vacuum hoses check out under the hood but something must have come loose. Can I look around where the hoses enter the firewall? Is there another way to track down a vacuum leak?

Many, many thanks in advance,
Matt