COuld a blown crank seal (leaks on the highway) cause a a poor idle quality? I know it sounds silly, but according to chiltons the crank case as well as the valve covers are under vacuum. If the crank seal is toast and allowing air in...aka a vacuum leack couldn't this cause rough idle? Has anyone ever heard of this?

I'm assuming the car is properly tuned and the spark plug wires, cap and rotor are good?

Some other thoughts.....

1. I did notice that my car seemed to idle a little better after I removed and cleaned all electrical grounds and contacts in the engine bay. Use elecrical cleaner and apply dabs of dielectric grease where appropriate. Pay particular attention to f.i. grounds. Also clean up the fusebox and replace any questionable fuses.

2. Cleaning the flame trap and related hoses did seem to make a slight difference - maybe just my imagination?? Definitely made the car feel a little more peppy though! So you might be onto something there.

3. Aye Roll's right, clean throttle body and replace gasket. Check AMM hose.

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90 244DL 1/4 million miles - original engine/drivetrain :)

No, if anything the system gets gummed up.
Vacuum leaks cause rough idles however, so keep on that track. I drastically improved idle in my old 86 by replacing the intake gasket and the split, cracked hose from the AMM to the throttle body. Steadied right out. Both of those are likely places for you to start.

The gasket is like $4 and the hose cost me $14 @ www.fcpgroton.com.

Also, injector seals can give you leaks, so check into replacing those as well. And if you haven't already, by all means tune it up, and remove and clean the throttle body while it's apart. That gasket is less than $1.
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Rob Bareiss, New London CT ::: Roterande Fläkt Och Drivremmar!

the intake gasket and the throttle body gasket are all less than 9 months old. the hose to the amm may be an issue however. i have a kit for injector seals but i am unsure of how to install. any tips?

The fuel injector seals are actually pretty easy, pull the fuel pump relay and start the car. Open the line (have a bucket to catch the fuel. The injector rail will lift off after taking off both bolts. After toging a little the injefctors should pop out of the the intake maniford. After you replace the seals on the injectors wipe out the ports on the intake maniford. There is dirt down inside the manifold. Make sure you get this out as it will make it easier for the new seals to do thier job.