Do not throw parts at it!



My 300SEL passes fine without EGR (it was plugged up at the intake plenum so I simply removed it all). Hell, I think Federal M103s in '89 did not even have EGR.

What are your emission numbers? Test the O2 for function, it is precat... if it was post cat it would be attempting to adjust scrubbed exhaust numbers. Remember, these big old cats like to be good and hot when you go to test.

Start with a full tune up, repair any oil leaks, fresh fuel, etc. This stuff is pretty inexpensive all things considered and will give you a solid baseline in which to retest the car.

Plugs
Wire set
Cap
Rotor
Oil service
M103s usually need valve cover gasket and 'U' shaped upper timing case seal
Fan belt
Any questionable breather hoses (probably most/all due to age)
Any questionable vacuum lines (probably most/all due to age)
Fuel filter
Air filter
etc

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]