New Member Needs Help
 

Hello everyone:
I am a new member in need of help.
I have found very valuable information in this forum. Before I ask my questions, I would like to let you know that I have done my homework and searched all the postings. I read the codes and they are as follows:
#5 EGR - used to be there before the work I did
#8 coolant temp sensor
#10 air flow sensor
I have a '94 E320 that is currently having idle problems, the idle flunctuates btw 300-1100 rpm, at all times, hot or cold. This happened only after some work was done on the car. These are the things I did to the car right before this idle problem occurred, I am not sure if my problem is related to any of these:
I changed the serpenine belt tensioner, changed the coolant, and cleaned the EGR crossover pipe. The pipe was clogged VERY badly, I had to disconnect it below the intake and clean it. I first tried to clean the pipe working through the intake by keeping the butterfly valve open and using a thin copper pipe with a speedometer cable to reach the pipe opening, this did not work. When veeping the butterfly opened, I was very careful not to damage it, I held it open by pushing the gas pedal to the end and letting the butterfly rest on a rubber pipe to hold it open. Could I have done any damage to it , although I was very careful and gentle with it?
I looked for disconnected vaccum lines but can't see any, I will keep looking though.
If I applyvacuum to the EGR, there is no noticable change in idle speed, but I KNOW that the pipe is CLEAN, I spent 2 hours cleaning it.
Is it possible that the egr is bad, but because the pipe was clogged the bad egr was not affecting the idle speed? And now that the pipe is clean, the symptoms appear?
It could be that the code#10 appeared b/c when I first started the car I forgot to connect the air mass sensor plug, however after connecting it, the idle problem was not fixed.
I think my proble can be a bad egr, or a vacuum leak, please help me with any ideas here. Before I did all the work on this car everything ran fine and only CE light with code #5 stored was on.
Help is very much appreciated.
Thank you,
Tony

Hi Tony , have you searched 'wiring harness' or anything like that? These cars are notorious for baking the harness , just a thought.. good luck.

I will have to agree with Kyle here. If it is the original harness I would suspect it is time to replace it.

I agree with the above two recommendations about checking your engine wiring harness. It is surely bad. They are all bad from 1993-1995 on 3.2 liter M104 engines.

It may (or may not) be causing some of your problems.

However, I don't think the engine wiring harness is causing your idle to fluctuate. It can be one of three things:

1. vacum leak: could be a problem with a vacum hose that has come loose or is not attached properly. You could also have a leak at the intake manifold gasket.

2. Mass Air Meter - A bad mass air meter will allow the idle to hunt up and down.

3. Throttle Actuator - They have potentiometers that wear out over time. The wiring harness for the actuator also goes bad for the same reason the engine wiring harness goes bad - flaking insulation.

New member Needs Help - UPDATE
 

First, thank you all for your replies. And excuse the length of this post.
I have had the car for only 2 months, however I am pretty sure that the wiring harnes has been replaced. This is because if you look at the DIY on mercedes shop there are pictures detailing the process and you can see that the new harnes although almost identical to the old one, it is slightly different, exacially on the connections to the thermostat. Mine looks like the new one, and it is not flaky.
Part of my problem is fixed. I looked for any disconnected vaccum lines and I found one big diameter line disconnected at the intake manifold, btw the intake and the cylinder head. I plugged the line back in and started the car. Now the idle does not nearly flunctuate as bad. Before it would go up or down by 400-500 rpm, now it is more like 10-150 rpm. I think I can still hear a hissing sound (maybe vaccum leak, but it is hard to accurately tell b/c of engine noise. Do I have another vaccum leak? I strongly belive that whatever is is due to the recent work I did on it. I worked around a few vaccum lines.
When testing the EGR, it does hold vaccum, and I can hear the membrane inside click (open or close noise), however, when the car is idling andf I apply vaccum it does not make that much difference. But, I KNOW the egr sover pipe is very clean.
Do you guys think I have another vaccum leak, or my egr is bad? The engine had no idling problems before when the egr crossover pipe was completely clogged. (It was totally clogged in the last 5-6 inches of the pipe. I think that now that pipe is clean, either there is an egr problem, or I must have damaged a second vaccum line.
When I broke a couple of vaccum lines in the very front of the engine, under the cover, I replaced 2 sections with a generic rubber vaccumn line from the autoparts store. The diameter of this line was slightly larger. Could this be a problem?
Thank you again.
Tony

Your EGR must be stuck. If you apply vacum and the idle doesn't changed, then either the hot inlet pipe is still plugged, or the egr valve isn't functioning. There is no other choice.

You might consider replacing the hot inlet pipe with a new one. The new pipes extend slightly farther into the intake manifold to prevent it from caking up with carbon deposits. If not, your current pipe will plug up again, although it will take several years.

tonyhito, can you detail how to remove the intake manifold to clean my hot inlet pipe? I am generating a code#5 for the last 2 weeks. I haven't messed with it yet because everything runs fine. Can the Egr valve br disable like in the diesel engines or does everything go haywire with the codes? I also have a 94 E320, thanks.

You don't need to remove the intake manifold to either replace or clean out the pipe.

You remove the pipe where it connects at the egr valve.

If you "disable" the egr valve, you will get a Check Engine Light.

The best way to disable it is to put a "BB" in the vacum line.

EGR hot inlet pipe
 

In order to clean the hot inlet pipe you do not need to remove the intake manifold. The easiest way to disconnect the pipe is from under the car. There are two bolts that hold it. The front bolt (when facing the engine can be removed from above, the rear one from below. If it is really clogged up like mine, use a drill bit by habd to clean out the manifold side, and just be creative with the pipe itself. You can use a coper wire, speedometer cable, etc. At the end I blew air from the egr end which I disconnected

How to detect vacuum leaks?
 

What is the best way to know if you have a vacuum leak and detect it if you have one?

To clarify. I cleaned the hot inlet pipe from the intake manifold side. This is the side where it gets most clogged up. Mine was so bad that cleaning it from the egr side did not do it.

Update - Please Help
 

Please read my first message in this thread for more background if you need.
My e320 is still having idle problems after I cleaned the egr crossover pipe. I know the following: the egr pipe is clean, the egr is tested and works. The engine first displayed codes #6 (idle control) and #10 (air flow sensor). I reset the computer and I have driven about 150 miles and no codes have apeared. CE light is not on. The idle continues to flunctuate, by 10 - 100 or so every 1 or 2 seconds. However, it seems to be geting more stable, but progressing VERY slowly. Is the ECU "learning" or something? I have looked for vaccum leaks but can't find any. Has this problem happened to anyone after cleaning the crossover egr pipe? Idle flunctuates when car is cold (1 or 2 min after cold start) or hot. It drives flawlessly, just when in idle it surges (N or P position does not matter). It seems to stay more steady when stopping after a ride on the highway, and then once you touch the pedal again it starts dancing up and down. Any ideas? Help is needed and appreciated. I have checked all the posts on the subject. I am in the process of "brewing" Arthur Dalton's tool. Will this tool help me to diagnose this problem? I suspect it is vaccum related.
Thanks,
Tony

Re: How to detect vacuum leaks?
 

One good way is to spray solvent (starting fluid, carb cleaner, etc.) at suspect areas. When the idle goes up, you've found your problem. You can also use propane by attaching a rubber hose extension to the torch head and flowing gas over suspect areas. Propane is less messy than solvents but more flammable, so you have to be careful.