Hey guys this is my second benz, first one is a diesel. I picked it up this week for a few songs. After looking at the interior I fell in love with it. I wish my 83 300sd was this nice.

its not passing emissions so I have a few things to do this week on it. I am going to start with the o2 sensor and egr valve. I looked for the o2 but didn't see it, is it before or after the cat? thanks in advance

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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]

I took it back thru yesterday for free and the numbers were worse than when the guy I bought it from took it. NC and Ox are failing.

I put a o2 sensor on and while I was at it, I hit the cat to see if anything felt loose. It was pretty solid.

I tore into the top last night, I found three hoses so far with split ends. One was the vent hose going from the air filter to the valve cover. The other two were the ones connected to the Air valve controller. All three have been ordered.

I went to change the spark plugs and all six wires broke on me. Have those on order. I changed the valve cover this morning and have the rotor and rotor housing on order. It looks like the cover will be a pain to change.

I will go thru the rest of the vacuum system and change anything that is loose or soft. Thanks for your input.

I have to drive about 20 miles to do the emissions so it is nice and warm during the test.

Use anti seize when you reinstall the plugs. Why people do not is beyond me.

The upper timing cover is not too hard to change, just somewhat of a pain. Check the three and four way vacuum connectors, those become brittle with age and create issues.

Fresh oil does help with numbers, sounds silly I know. Something to do with blowby and whatnot.



Failing Nox can be too lean (think of your vacuum leaks...). HC is unburned fuel usually. Post the numbers if you can please.

__________________
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]

Nox 6.22 (2.5) is the limit, HC 1.70 (1.60) is the limit.

As of this weekend, Thanks to Hogweed for hooking me up with a fuel line.

I now have replaced the fuel injector seals, new spark plugs, wires, dis cap and rotor (these were really needing replacing), Air filter and O2 sensor replaced. Fixed a hand full of vac lines. Gas smell still exists, I think it is coming from the black box on the fuel dist. I can get another one off of a 420 sel.

Took it thru emissions again today and it was worse than before. Hc 1.99 (1.60), Co 8.98(15.00),NOX 5.95 (2.50).I guess it is time to take the plunge on the cath converter. What do you guys think? It was warmed up, during the tuneup part I found a small leak on top of the radiator. I will replace that this weekend along with the thermostat.

went thru and replaced any loose vacuum connectors, belt adj ect. The engine poooors pretty good now. RPM's at idle is between 650 and 750.

After all that and a bottle of 91 percent rubbing alcohol, these are the numbers,

HC .34 has to be less than 1.60

CO 2.02 has to be less than 15.00

NOX 1.70 < 2.50

now I have to change out the exhaust man on my 83 300sd.