Hi Folks,

I have been hitting my head against the wall trying to fix Code 5 on my 95 E320 W124 wagon. I have seen plenty of discussions on the EGR issue with W124s so I am hoping folks here can point me in the right direction. I have been chasing down everything I can find on the forums and it has not gotten me anywhere.

My observations thus-far:
-EGR itself works fine. Pops when vacuum applied, snaps back when vacuum is removed. I cleaned the EGR tube anyway and also replaced the gasket at the throttle body side.
-I have steady vacuum going into the EGR SOV, but no vacuum coming out.
-I just installed a new SOV (new from MB), but still no luck.
-I cleaned the corrosion off the electrical leads and confirmed I am getting voltage at the leads. The EGR side was about 12V the smog pump side was around -13.5V if I recall correctly.
-Here is where it gets weird. After I cleaned the leads and reinstalled, I had vacuum at the SOV to EGR outlet. Two days later, the CEL came back on and I am throwing code 5 again. I checked the SOV and now there is no vacuum. I don't know if the dielectric grease I put on the leads could be part of the problem, but I figured I'd include that detail.


This problem has been driving me up the wall. I love this car and want it to be running perfectly. My mechanic told me the EGR is quite likely the cause of my rough idle. If anyone can help me figure out what I am missing I would be eternally grateful.

if you cleaned the tube and the valve is good I think the experts here would agree it must be the ports in the cylinder head that are blocked. Small passages at each exhaust valve which carbon up. I rebuilt my head in this car and the machinist did a great job cleaning these ports. Im not sure if seafoam cleaner or other solvent processes can do it..

And Im not sure if I agree that blocked egr passages will cause a rough idle..

I will be curious to see the comments on this.

Look at the switchover valve and map sensor on the driver's fender. It may not be a problem with the EGR per se but a problem with how it's function is monitored.

__________________

90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs 1st Gear Start

90 300CE 104.980
Milled & ported head, 10.3:1 compression
197° intake cam w/20° advancer
Tuned CIS ECU
4° ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff

dux, what exactly do you mean by look at the valve and map sensor on the fender? I am fairly new to maintaining the car, so I do not know what you mean.

Also just to clarify, my current issue appears to be the SOV is not working even though it is brand new... I am getting vacuum to the SOV but not past it, so the EGR isn't opening up. It worked briefly but seems to have stopped working, so I am going to speak to the vendor and see if they can replace it or give me a way to test for proper function. Outside of that I am stuck.

I hope it helps with the idle because I am running out of things to replace/fix to smooth it out hah.

The function of the EGR is checked by watching the engine vacuum during certain decel conditions. The MAP sensor reads engine vacuum but in a lot of models in that time period (including yours, I think) use a switchover valve to switch between reading engine vacuum and fuel tank vapor pressure. A failure of the MAP sensor or the switchover valve that selects it's signal source can cause EGR faults in an other wise functioning system.

This of course assumes a functioning EGR system, so you need to get that switchover valve working before diagnosing further.

Discounting an EGR valve that is sticking open, it should have no influence in idle quality.

__________________

90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs 1st Gear Start

90 300CE 104.980
Milled & ported head, 10.3:1 compression
197° intake cam w/20° advancer
Tuned CIS ECU
4° ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff

gjones8131, did you disconnect the EGR tube from the inlet manifold and clean the port in the inlet manifold? That connection is difficult to access, plus there is tubing clamp on the oil filter housing that must be removed so the EGR tube will pull out of the intake manifold. When I disconnected the EGR tube on our 1995 E320 the port had a light caking of carbon which was easy to remove. Cleaning that port cleared the EGR warning light on the instrument panel.

__________________
Fred Hoelzle

Thanks for the info on how the car checks vacuum, good to know. Currently working on a 12V source to test the new valve's function.

I cleaned out the tube a few months back. Checked it with a hand vac, runs real rough when I apply vac. I checked the valve separately and it can hold ~20 In Hg for a few minutes with no leaks.

Update.

I have confirmed new SOV functions properly. For that matter, the old one works well too :/ . The valves audibly click when given 12VDC, and the vacuum on the SOV intake drops to nothing with voltage applied.

I am not familiar with car electrical stuff, so if anyone has any thoughts on this it'd be much appreciated. I did check my fuses and they are all good, upgraded them to all copper/bronze anyway since the aluminum was looking old and oxidized.

Clean the tube. Clean the tube. Clean the tube. It is located on the LH side of the engine. After removing the end of the tube I used a wood screw to clean the carbon build-up and the fault code did not reappear after reset. Please search the posts to define exactly where the tube is attached - I want to say the exhaust manifold. You access the tube from underneath the car.

I did this many times on my 95 E320.

__________________
Tom Latos
2002 E320
1995 E320 Sold at 288kmiles

Sigh. I cleaned the tube first. See the original post.

gjones8131, how did you go about cleaning the EGR tube? If you pushed a line through the EGR tube where it connects to the EGR valve and did not disconnect it at the intake manifold to clean that port, you may have only made the condition worse and not actually restored the functionality of the EGR tube.

__________________
Fred Hoelzle

I cleaned it very thoroughly as follows.

-Remove EGR valve from exhaust manifold, clean inside gently to remove some tar
-Soaked the tube connecting manifold and EGR in carb cleaner to remove all tar
-Removed EGR from air intake and ran a tube from it to under the car into a bottle to collect crap, soaked the EGR tube in cleaner (with a stopper in the outlet tube to let it really soak) multiple times for a whole day using a speedo cable and some air. By the time I was done any cleaner in the exhaust side immediately ran out the intake side
-Cleaned the little port in the intake thoroughly
-Put in a new EGR gasket

I checked the EGR valve while I had it off the car and it seemed to be functioning properly

So you are still getting code 5 and the idle is rough. Curious how your EPA test for emissions has gone. These cars run VERY clean and way above limits. Usually..

I still suspect some other issue is at stake here and speculate the code could be misleading. Hope you get it fixed and let us know.

gjones8131, if the idle is very rough ... as in considerable engine shaking ... you may want to perform a compression check on all cylinders. I chased a rough idle on a 1995 E320 for months without any success. Finally I went to a local independent tech for a professional diagnosis. He quickly found there was no compression in cylinder No. 1. The tech explained that he had never experienced a valve problem like that in a 104 engine. I distinctly remember the engine changing from running smooth to running rough. Whatever the valve failure was, it occurred instantly. The engine had 198,500 miles on it ... much less than I expected to get out of our "snow car".

__________________
Fred Hoelzle

The code doesn't come back right away when I clear it, but sure enough within a few days it is back at code 5. On one occasion, it threw codes 10 and 26 a few days after I cleared 5. When I cleared those, code 5 came back.

I will definitely have to look into a compression check. This car has been idling rough for a very very long time (it was a family car that just became mine) and I have managed to smoothen it out by putting in a new voltage regulator, new gaskets on the air intake, and a new air filter. Currently I feel the car revving up and down between 600-700 rpm when warm, and then it dips down and idles real rough. It only occurs in drive and I haven't had the chance to look under the hood while its in gear, so I don't know about how much the engine shakes. I plan on replacing the mounts after I get the codes taken care of. We will see how it goes