I just purchased a 1989 300SE with 155K miles. The vehicle had been sitting idle for several months before I bought it. I had a leaky valve cover gasket that I just repaired. The vehicle will not pass the Masschusetts emissons test. I was told by the technician who conducted the test it was running rich. I have put in some techron fuel additive and replaced the plugs. Several of the plugs I removed were wet but nothing outrageous. Do I need to make a mixture adjustment or continue to run to get rid of some carbon build up?

Yes. Because the car was running rich you need to adjust the fuel/air mixture.
You need to turn it counter-clockwise to the proper level. First try 1/8 cycle and see the emission.

__________________
Master Computer Engineer, A+, Network+, MCP/MCSA/MCSE 4/2k/2k3 - Messaging, MCTS, MCITP, MCT, Brainbench, ICDL and starting Ph.D

380SE 1984 <------- Totaled by flipping accident
300SE 1988 <------- Sold
Volvo S70 2000 <---- 4 family
Opel Omega 2002 <-- 4 family
560SEC 1989 <------ Sold
560SEL 1990 <------ Sold
560SEL 1991 <------ 4 my mother
560SEL 1989 <------ Sold
600SEL 1992 <------ Current

http://search.ebay.com/_W0QQsassZkhazenzcc

Here is a link to an article on fixing vacuum leaks.

http://www.peachparts.com/Wikka/M103VacuumLeak

I suggest you replace all the plastic 4mm vacuum lines and rubber elbows, the idel air bypass hoses, the injector holders and seals. There is a large rubber section under the CIS horn that may also leak.

http://www.landiss.com/mixture.htm

and this one on changing the mixture and monitoring it with a voltmeter, preferably one with a duty cycle setting, available at Sears for about 30 bux.

You need to check the EHA current, the small black box on the side of the fuel distributor.

Please post your emission numbers.

__________________
Regards

Warren

Currently 1965 220Sb, 2002 FORD Crown Vic Police Interceptor

Had 1965 220SEb, 1967 230S, 280SE 4.5, 300SE (W126), 420SEL

ENTER > = (HP RPN)

Not part of the in-crowd since 1952.

Warren thank you for the input. Here are the emisson numbers:

Reading Limit
HC ppm (Idle) 0358 0220 Fail
CO% (Idle) 03.68 01.20 Fail
HC ppm (2,500 RPM) 0042 0220 Pass
CO% (2,500 RPM) 00.11 01.20 Pass

This test was run with a tank of 89 octane. After failing the test with these results and realizing the error in type of gasoline I filled the tank with 93 octane added a can of techron additive ran about 75 miles on the highway, and tried to retest (the additive was stil in the tank). The test stand would not allow the test to run to completion it kept requiring longer test times until the tech gave up. Since then I replaced the plugs (as described in my original post) and have a fresh tank of 93 octane with no additive.