Help! My car is getting worse by the minute
 

Friday night I drove by the Auto Zone to have them read the CE light for me...It turns out I may have a clogged or bad EGR valve.

That was the only error code. I went home and Sat, I went in and took the EGR valve off to clean it and the tubes...While I was in there, I went in and changed the spark plugs. I put in some cheap Autolites...

When I was done, I had this terrible idle problem that got worse when you shifted into rev or drive. I thought it might be the autolites so I put the Bosch originals back in...no luck. I then remembered one of the boots off the coil was split a little at the bottom...

So I put a new Bosch wire set and NGK plugs in today....Guess what? Its even worse than before...Im beginning to get scared touching the car...Anyone out there seen this before or have any idea what it could be?

Would the EGR valve cause that much of a problem? Also, their is a huge hesitation with the car, like Im pulling a boat...

I took it back on Sat, and had AZ read the codes again...came back with EGR and misfire code....it was a multiple cylinder misfire code.

Thanks in advance for any help


Carlos

Sorry
 

Sorry, forgot to tell you which benz...its a 94 S320 with around 134K miles.


Thanks,

Have you replaced the supressor boots that connect to the plugs.

A misfire is usually a bad connection between the coil wire and the boot.

Are the NGK plugs resistor or non-resistor?

Your resistance is in the boots, and regular resistor plugs give waaaay too much resistance.

Your problem might not be a clogged hot inlet pipe.

Because you have a bad idle when the car is cold, it sounds like your egr valve is either sticking or stuck in the open position.

Thanks for the info Paul
 

Ok...I replaced all the wires...I had to buy the entire set...so there were three new Coil boots, and then the three wires...Could I have hooked them up wrong? I tried to be very careful matching them up...or would that screw up be really evident?

The plugs I replaced the Bosch with are NGK resistor type 7938. I replaced all 6...gap i left at factory of .32

I did check all connections...I guess Im going to have to go in and check again. Maybe posting a pic of my problem may help...I may take a few pics once I get everything off.

Here is a pic with cover off...
 

Here is a pic of what Im working with...from what I can tell, they are all hooked up ok...

Could the timing have slipped? I did drive the car around a little...or is the EGR valve really that important, and would it make a my car run like crap?


Thanks,
Carlos

Double or triple check that the wires follow the firing order. It is easy to get a couple wires crossed which will make you engine run horribly and give you a multiple misfire code I bet.

Triple checked wire placement and fit
 

Ok...I went in and double and triple checked the wire placement and the fittings on all 6 cyls...I followed the diagram on the cover plate...which is:

1 Cyl to 6 cyl coil
2 Cyl to 5 plug
3 Cyl to 4 cyl coil
4 Cyl to 3 plug
5 Cyl to 2 cyl coil
6 Cyl to 1 plug


I guess some of the above are redundant...but I wanted to make sure...All the fittings are snug...I dont remember how much play the coils should have, but I cant seem to push them any further down on the posts.

Looks like Im going to be going to work late...Does anyone know if I can damage the car driving to my local shop with the car misfiring?

And can the EGR valve really cause this much headache with the loss of power and erratic idle? This is the only other item I touched this weekend...Almost makes me want to give up working on these cars...I thought I could improve performance, and instead Ive created a complete nightmare.

Thanks for everyones continued advice and support...

Carlos

Re: Thanks for the info Paul
 

Like I said before, the resistance is in the boots, not the plug. You are creating waaaaay too much resistance with the resistor plugs.

Why don't you follow all of the advice that you'll find on every thread about plugs? Only use original Bosch copper plugs, non-resistor type.

There are now so many variables since you've changed so many things that it's hard to tell what's wrong.

You had a code for an egr valve. You cleaned the tube and the egr valve.

However, an egr valve can't be cleaned. The diaphragm either opens or closes normally, or they start sticking (in the open or closed position) or they get stuck permanentyly (either open or closed).

Since you still have the egr code, why don't you change the valve?

Looking for one tomorrow
 

Ok...i guess thats the next logical step...to replace the EGR valve...Is this it? I took a picture of this to make sure this was the part. This is the one that I took off and cleaned anyway. Its on the passenger side right on top of the manifold.

Also, would this little part cause the misfires and hesitation? The car sounds terrible when its in Drive or Rev..when in park, it idles right about where it should, but you can def here the "pinging" Giving it some gas and it will smooth out, but when you let the gas go, it drops down below idle and almost dies. Driving is ok at higher speeds, but acceleration is gone, and shifts are even harder than usual.

Read this article by Steve Brotherton -

http://www.peachparts.com/Wikka/EngineControls

Actually, skip to the last couple of paragraphs. Steve describes a problem with the M104 engine wherein the PCV system deposits soot in the intake manifold and that somehow causes an EGR fault. I don't have an M104 so I didn't read it carefully.

Sixto
95 S420
87 300SDL

I'd go back and read what Paul had to say about the plugs. The resistance should be in the end that connects to the plug; not the plug itself.

By using a resistor plug, you've increased resistance or put another way, created a "plug-missing" situation.

I'd deal with that first.

My 2 cents.

Anyone else feeling sympathy for this car?

Your case is so similar to mine. I also have an S320 1994 and recently I decided that I was going to change the spark plugs myself. I did the job and everything was fine. A few days after I noticed that the car was shaking a bit and decided to check if there was something loose or so. I noticed that one of the boots was cracked. After disconnecting and connecting all the wires again the car was fine. I decided to buy the new boots and replace them. After replacing the boots I started the engine and the car was shaking very badly. After connecting and disconecting the coils and the wires several times times the problem got worse. It came to the point that the car did not start at all. I took it to the mechanic and found out that it was the engine wire harnes. I think that you should not use the car untill you check out this harnes. At my mechanic there was C class mercedes that had a bad harnes and it damaged the ignition system, instrument cluster, computer, etc. I saw the old part after it was replaced in my car and I was impressed of the poor quality and the incredible bad shape of the wire insulation. As a matter of fact I preparing a letter and I am also sending the part to the Mercedes Benz Engineering Department. Good luck and check out this part, it seems to be a common problem.

I agree with 'rjcarrasquel's' comment about the possibility of the engine wiring harness being the culprit of your miss-fire.
It is possible that insulation on one of the coil leads (3 in all) has crumbled as a result of handling them during the spark plug change.
This happened to me. The misfire at idle was a constant and quick 'thup,thup,thup,thup'. Not an arrhythmic stumble or cough like one associated with a bad lead shorting out in damp weather. I was able to confirm which coil lead it was by moving them a bit with a piece of wood while the motor was running. The misfire would come and go when this was done to the culprit lead. I then carefully sliced the black tape on the lead to expose the two wires - and sure enough - the wire's insulation had crumbled off allowing them to cross and thus causing the misfire.

If this is the case with your 104, you can try to re-insulate the exposed wires or replace the harness (I got mine through Phil at the parts shop). Be sure and get the correct part number where it runs in back of the battery.

Making progress!
 

I have read everyones threads, and luckily have started to make some progress.

This morning, I broke down and bought and replaced the EGR valve...(201.00) from the dealer...I would have gone throught fastlane, but I needed the part yesterday.

The car roared to life, and I took it for a test drive...IT HAS NEVER RUN THIS GOOD SINCE I OWNED IT! It was nimble, and it purred like a kitten.

When I got back, I was going to put the plug plate back on, and decided to go ahead and replace the plugs with these NGKs metioned above...

I replaced, and sealed everything up....now, I am getting the hesitation again!!!!! I cant believe it! Im going to take these plugs off and go throw them at the guy at Vans Auto Parts.

Anyway, I know now that it was a bad EGR valve... I cant believe how bad it would make the car run, so, this is definitely something you want to check if you are experiencing unexplained misfires, and hesitation. I will post a pic of location and procedure if I get a chance later...I have to go remove that engine plate one more time to change the plugs once again!

Oh getting in and replacing the EGR valve is a snap...takes about 10 min to get it off...and even less time to replace...

Thanks,

Carlos