Help save a beautiful smoggy w124 wagon from the scrapper!

[208]

So i was able to get this car for next to nothing from a former classmate who abandoned it in the DMV parking lot for the city to take when it wouldn't start.

I got it home and cleared that up. (fault with the security interlock related to a break in attempt).

Now im on a quest to get the thing to pass california smog. All i know is that it didnt pass, she lost the paperwork form the test station...I had a brief conversation with her previous mechanic, and he said he had jumped something related to the mass airflow sensor, but it made the results worse.

its a 95 E320 M104 w124 wagon. Its not showing any engine codes or CEL, but could that be due to not driving it for long enough, ive had it for a month or two and only ran it to move it for street cleaning, If i remember correctly from an older w124 you have to drive it for about 20mins to get the codes?



Experts: Where should i start? Looks like a common issue is EGR tube blockage? wouldn't i be getting a code? Can i test this with a hand vacuum pump?

Other weird things: When i first start the car up and give it a little gas to get out of the parking space the engine will sputter and stall, once it warms up its not as bad.


I live in the Bay Area and smog tests for this car seem to be expensive, around $100 a pop. So id like to try some easy/cheap things before i send it it in for the first test.

[TnBob]

Get a copy of the prior test

[208]

Unfortunately i cant, she lost the papers..

Someone on another forum suggested that it could be an issue with the engine wiring harness. Though i dont see why that in itself would cause it to fail smog, but not return any engine codes.

[Stretch]

If you are dedicated to the vehicle the first thing I'd do is do a decent service. Clean - look - and measure!

Read the FSM on how to perform tests. The W124 FSM is available for free download via MB USA at www.startekinfo.com

[PARSHOOT1]

Well you've come to the right forum, did you use the search function to see if other members might have encountered a similar problem.

[MAVA]

This is the biggest problem with M104's that do not have 722.6 transmission. Mechanics do this jumper thing, but what I have found is the computer module that drives the smog-air pump shorts-out, but only smog-air channel shorts out, and register a "check engine" light. Note, the smog air pump channel is tied in parallel with the egr control air control solenoid. The solenoids that enable the EGR valve, and the smog AIR valve are located under the black plastic cover at the front of the engine, and one can test each solenoid by applying 12v and blowing on one side of each solenoid. The node of vacuum that feeds the solenoids that ultimately drive egr, and air valve is located under the front of the intake manifold. follow the plastic line that leaving the solenoids to the right, and make sure it is not cracked, or broken, yet the tubing where it ties under the intake will have a nipple, and the connection is a piece is made from rubber which tears, or gets soggy like a marshmallow. Also a rubber WYE is right there too, check the wye for integrity, and blue little inline looking filter which is a check valve.
Now, the vacuum lines to the left leaving the solenoids will disappear into the valve cover top cover. You will need to take that cover to see if the plastic lines are complete, and in good standing, and those two lines are the ones that drive the EGR and Smog air valve.

On the passenger side of the engine right below the center of the valve cover, their exist two diaphragm valves exist. One is the EGR, and the other is smog-air valve, yet each valve has a little rubber hose attached to each nipple. If you disconnect the hose, attach a three to five foot piece of vacuum hose to the nipple of each diaphragm, and suck on each one. Each should hold vacuum. I want to say the rear-most valve is the EGR. If the engine is started, the engine RPM settles after a minute or so. The hose long vacuum hose is attached to the valve if you suck on it. The engine rpm will start to cough a bit, and maybe it will even cough to the point that the engine has a very rough idle. Wants to turn off that indicates the EGR is working, and the EGR channel is not blocked.

The smog-air valve will only work when the smog pump is working, so to turn on the smog pump the drive signal voltage from the computer need to drive the clutch on the smog pump. If that does not work, then one can drive the clutch from a external 12v source, and then apply vacuum to the smog air valve, and the pitch/tone will change...

Now, you can have another problem, so have your codes read, and reconnect the MAS-airflow, and get a one day permit to drive it for 30 minutes to 1hr to get the code, but this is the most common problem to smog problems in California, and 1/3 of the cars I see have some kind of problem with something I just outlined..

If you find the smog pump is new(or the electrical connection disconnected), or one or both solenoid blocks are new. That is a clear indication that the computer has shorted channel, and the failure is Mercedes should have driven a relay to drive the smog pump, but on the M104 the smog pump is driven directly from the computer... In most cases you can use the computer module from a C280 to a S320. Just make sure you are in the range of 94 to 96, ANDDDD the car you are taking this from does not have new smog air pump or solenoid block, but at the local Pick N Pull junk yards in the San Francisco Bay have these cars, and these computers are rarely missing on those junk cars. Check the row52 site for cars...

Row52 | Search Results

I have been through this twice, and the very first time was a brain-busting for a few months. The second time was a easy fix because I knew what to do...

Enjoy,

Martin