1993 300E M104 Failed Smog HCs & DTC Readings
 

Okay, so it's been awhile since I've gotten a post out here to you guys... but I have a couple of independent mechanics that I've "accrued" throughout the years that help me out with this old car.

So I crashed my 2004 E500 in June... I was totally fine... but I had 217k miles on that car and she drove like a champ still! A/C wasn't working... and the transmission has just been rebuilt at 197k miles on the ORIGINAL tranny fluid... and I drove that baby HARD. And I digress....

So I decided I didn't want a car payment... so I bought a 1993 300E off craigslist for $1200 cash (did a cheaper version of carfax... clean title.. and had one owner at 107k miles in 2007).

Needless to say... I have pumped some dough into it! New brakes and pads all around... new water pump... and head gasket failure! Thankfully I got a steal and with parts, had it done for about $1400! This included new spark plugs and plug wires and a fan clutch. Additionally the head was machined... not sure how involved they got with the valves (I've heard this can be a smog issue)...

Okay, so the car drives GREAT! Needs a couple minor things such as some suspension components, a WORKING heater (AC works GREAT!), and a decent reverse gear would be nice!! Reverse works, but it's a B*TCH! I know I know, the B3 seal or whatever.

So my car fails smog miserably with a rating of 330 and 350 for the HydroCarbons (HC), max allowance is 250 and 280, respectively. BTW, this is in California.

So I have done some (quite a bit) of research and have deduced the high HC emissions due the catalytic converter, the egr valve, O2 sensor, vacuum leaks, smog/air pump, ignition COILs... and I think that' it (please tell me if I'm missing something)...

Ok, so I have a new O2 sensor that I'm having installed today... and I'm pretty sure that the cat would be making some rattling noises if It were going (wouldn't it!?).

THUS, I should read the codes, yeah!? As it turns out, when I purchased the vehicle, I didn't notice that the CHECK ENGINE bulb (AND SRS!) aren't there! So I'ms ure the MIL is on.

Moving right along... so I purchased the parts from radio shak (led, resistor, banana plugs, momentary push button) to assemble a DTC reader. As it turns out, my 16 plug deal HAS a Push Button (pin 2), AND an LED (pin 4), which lit up when I pressed it! So I'd like to read the codes... but can't find anywhere (even in the 169 pg PDF file by MBenz on reading the DTCs from 1988-98) that includes a built in LED and push button... I'm sure it's OEM...

In conclusion... what GIVES? I need to pass smog as the car isn't really even legally allowed to be driven and I already got the 30 day temp deal from the DMV. What do I do RE collecting the fault codes (# of flashes) from the built in "code reader" I'm sure I need to do something with the banana plugs... but WHAT, and WHERE?

PLEASE HELP!! Thanks guys! Nice to be back!!

I'd for the meantime fill it half full of e85.Then take my time to get it sorted out.

what are the chances this will work? 50/50? 20/80?

10/90? Any wild guesses?

40% got my M104 though NJ inspection. Added alchohol purchased at hardware store. Car failed twice, high HC at idle. Cat rattled.
Later found out cat was empty.

So ASSUMING my cat is still good.... is that a 40% mixture of e85 or a 40% chance to have it pass?

Welcome back to the forum.

When I had my 1993 300E (3.2), it would fail smog at every test.

Installing a new cat for about $200 allowed it to pass.

Sun Valley transmissions in Van Nuys is the place to go for your transmission.

A visit to Sun Valley Transmission, Van Nuys, CA

THanks, Suginami! Nice to hear from you.... Did the place Tranny place in Van Nuys do your cat too or? And was the $200 for new cat installed, ie Out the Door Price? Also, where your HC's really high?

Code readers are cheeeep on fleabay

Sun Valley rebuilt my transmission, as they do just about all of them here in So Cal. I bet nearly every Mercedes independent shop uses them.

I had my cat replaced by a local, hole in the wall muffler shop with the cheapest, generic one they had. They only worked long enough to pass one smog test, but it was only $200-ish.

What engine is it? What is the o2 sensor telling you?

How die hard diy are you? I'm in process of rebuilding a 722.4 and it isn't the monster people make it out to be... However, I was going to go through Sun Valley before I decided on diy.

1993 300E's had the M104 motor... 3.2 inline 6.

Had 02 sensor replaced. NOtice no difference (not that I expected to). Will either use home-made code reader tomorrow and get some TC's finally... maybe new CAT is in order. THanks for the help and I'll keep you guys updated...

(EGR valve likely the culprit?)

I'm not that much of DIYer... I can change oil, change parts, ID them, try and diagnose and am generally familiar with all the components and systems.. but not like a mechanic by any means.

Also.. I'm not having any transmission problems.. so don't jinx me! ;)

If you have a vac gauge and infrared temp gun the egr is a 10 min test. Pump up the egr to see if it holds vac. If pass, hook the vac gauge up to the output of the switchover valve. When warmed up rev the engine (should be able to move the throttle behind the aircleaner, but I have a m103 so not sure) and the gauge should jump with the revs. Also the temp of the egr tube should change when measured by the temp gun if not clogged.