Original post is below, I have since found a small leak in the intake hose between the AMS and TB. Thought that might throw things off a bit as well. I've taken the suggestions made previously and will attemp to pass again tomorrow. I'll let you know if I pass.



'88 240DL
Failed GA emissions
High on NOx in both 25/25 and 50/15 tests by about 600-700 ppm
(this is about 50% above acceptable #'s are as follows)
Reading/Allowed Reading/Allowed
1763/1163 1914/1273

Other tests (HC & CO) were OK

I tested for vacuum leaks and there are none.
The timing was retarded about 4 degrees from where it should have been so I reset it to 12 BTDC per spec.
Car has recently gotten new ignition components including O2 sensor, plugs, wires, cap/rotor.
Exhaust downpipe is tight, no discernable leaks.
I Seafoamed it.
I plan on adding some octane booster since the tank was just filled.

My question is, could the retarded ignition timing be the primary cause of the high NOx readings I am getting or is the reading too far off fot it to be just that? If so, have I missed anything besides checking the CAT?

Bob K

'94 945T
'88 240DL
'84 242Ti
'89 560SL
'88 300TE
'68 GT500KR