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  #61  
Old 09-17-2003, 07:05 PM
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Join Date: Jan 2003
Location: Matthews, NC
Posts: 1,356
Can-Do,

My car started fine when cold, and idled good when cold. As the engine warmed up the idle would start out OK but after a min or so, it would start missing a little and then after 2 min or so, it would have a "dead miss" on one cylender. Also when it was started after it was warmed up, it idled rough with this "dead miss". After you started moving, the problem went away until it idled for a short time again.
I found the problem by letting it idle until the miss started. I then turned off the engin and removed the plugs. One of the plugs was black and the rest were tan. The cylender that had the black plug was the one with the bad injector. When I tested the injector, it had a very slight leak. I tested it by removing it from the intake manifold with the fuel line still connected. I then put a jumper in place of the fuel pump relay so it would keep fuel pressure up. I then watched the injector and saw it drip very slowly. I swaped it with another one of the injectors and the the same injector still leaked. Swaping the injector with another one proved the problem was with the injector, and not the fuel distributor. I replaced the bad injector with a new one, started the engine, let it idle and the problem was gone. This whole process only took 15 to 20 min of my time. The injector only cost me $23.oo. Problem solved. Then and only then did I replace the other 7 injectors.
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84 500 SEL (307,xxx miles)
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  #62  
Old 09-18-2003, 09:29 PM
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Location: Tucson, Arizona
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Thanks

Thanks Paul, for your input. I haven't had the opportunity to pull plugs and check for the leaking injector yet. Might be a good idea at any rate to change out the injectors, but I'm curious to see if I have one or more leaking down that may be causing the problem. Have you changed any other items in your attempt to solve this problem besides the injectors? Just curious as many have gone through several items before coming to this point.

Thanks,

Charles
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"Tell me and I will listen, Teach me and I will learn, Show me and I will accomplish, Involve me and I will succeed."
'84 300SD 256,000 Gold on Brown (Mileage Award)
'86 300E 246,000 Blue on Tan
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  #63  
Old 09-19-2003, 08:55 AM
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Join Date: Jan 2003
Location: Matthews, NC
Posts: 1,356
Can-Do

No I didn't change anything except the injectors to fix this problem. I refuse to throw parts at a problem. I only replace parts that are causing a problem. I work very hard in my shop to diagnose problems and replace only what needs replacing. We have people call and say they want a tune-up. Our first question is WHY? Usually we find that they have a problem and asume a tune-up will fix it. We find the problem, then and only then will we "tune-up" the car if it really needed.
This isn't to say that I don't do regular maintaince. My cars are maintained better than most, I just don't do maintaince to fix a problem. I fix the problem first, then do the maintaince I feel is needed. This applies to my personal cars, and my customers cars.
If you feel you need injectors, then do it AFTER you find the problem.
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84 500 SEL (307,xxx miles)
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  #64  
Old 09-22-2003, 10:14 PM
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Location: Tucson, Arizona
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Paul,

You hadn't mentioned before that you were a mechanic shop owner before, great to here from some folks out there with expertise in the field. Do you do general mechanics of specialize in Benz or foreign auto's? If I can find a day off, or get the days stretched a little longer I'll pull the plugs after the rough idle as you suggest. At present I'm seeing dark going to and coming home from work so it will probably be several days before one comes available that I can get free. Have you seen any other instances where the idle on the car became rough such as a Benz, where it wasn't the injectors or fuel or vacuum related?

Just Curious,

Charles
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'84 300SD 256,000 Gold on Brown (Mileage Award)
'86 300E 246,000 Blue on Tan
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  #65  
Old 09-23-2003, 07:45 PM
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Join Date: Jan 2003
Location: Matthews, NC
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Can-do

I specilize in the electrical/computer systems in any brand of auto except VW (I refuse to work on a VW, lost all the money I can afford on them). But I also do most anything the customer wants including mechanical. In the last 19 years I have cultured many good customers who come to me when they have a problem of any kind. This takes most of my time. I spend the rest of my time working on electrical problems.
I have several customers that own MBs and I also repair/maintain them. When I bought my 84 500SEL I only paid $500.00 for it. Half of the engine was under the hood, the other half was either in the trunk or missing. I pieced this car back to life with whatever used parts I could find. Of course, any maintaince type parts (brakes, hoses, etc) were new. I will have to say after about a year, this is the finest car I have ever owned. Also, I have learned more from this car than any other I have ever worked on.
I have seen many leaking injectors on many other brands of cars. Some only affect idle, some cause other running problems. However vacumn leaks are the most common idle problems. But usually, they idle bad any time they are idling. I believe I remember that yours idles good at first, then gets bad after a short time. Is that correct? I'm sure there are other things that can cause this but injectors (or float level on carburators) is the only one I have ever seen.

Checking the plugs is the best way to find this problem. When you get time to check them, let me know what you see and we will go from there.
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  #66  
Old 09-27-2003, 10:50 PM
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Location: Tucson, Arizona
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Checked out spark plugs for fuel

Greetings Paul,

I got off work early today, before sunset anyway, and had a chance to run the Benz to the rough idle situation, or really a missing situation then shut it down. I pulled all the plugs and found nothing out of the ordinary. The first and last plugs were a tad more crystalized with a brown substance than the rest, but all plugs were dry and actually clean looking. I changed out plugs about 11,000 miles ago and after a putting them all to a wire brush they all looked new again. I don't think the problem is in the fuel system as far as a leaking down injector. Let me give you a run down on todays starting and running events on this car.

After sitting over night I started the car about 6 pm the following evening and starting was extremely difficult. I tried to start it using the gas pedal and it would bump off then die. I then tried to start it using no gas pedal and it idled rough for about 15 seconds or so and finally stayed running. I slowly idled it up past 1000 rpm until it stayed running without missing. During this time the antilock light stayed on the entire time and about a minute or so into idling the light went off and the idle went up to about 850 from around 650 and things started to smooth out. I decided to take it out for a drive to reach operating temps and the engine kind of missed as you mashed on the pedal for acceleration, seems like on one cylinder. I drove it out about five miles and returned home and left it in drive as I popped the hood and started checking spark plug wires pulling them one by one to feel the engine difference and all of them seemed to make a difference when disconnected except the number one cylinder than didn't make a huge difference but could feel the miss when it wasn't attached. Seemed like the sixth cylinder was pretty much the same way, so in between cylinders definitely seem to drop out if they aren't operating correctly. After cleaning all the plugs and reinstalling them the car seemed to run a tad bit better but still stumbles a little bit on hard acceleration, think it might be spark plug cables or ends? Only a few seemed weak when pulling them off as far as a spark to ground, the first one is one of them. I noticed the antilock light finally went off and the rpm raised and some of the idle problem subsided so I pulled the OVP after I got home and dismantled the case to find green corrosion on the inner terminals, so I cleaned it all off and painted the circuit board and will try it out in the morning to see if the cleaning made any affect of it's operation. All solder connections in the ovp seemed solid otherwise. I noticed when looking at the dist. cap the other week that there was a heavily carboned terminal and I cleaned it up as best as I could. I did order a new cap and have it in hand and will change it out sometime here shortly, as soon as I order the lower dist. cover as removing the cap basiscally destroyed the lower cover. Do you think this could be the problem as well as the cylinder one not being as hot as the rest? Have you seen the spark plug cables themselves break down in the past, or is just replacing the spark plug connector end going to do the trick? Any thoughts are much appreciated.


Thanks,


Charles
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'84 300SD 256,000 Gold on Brown (Mileage Award)
'86 300E 246,000 Blue on Tan
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  #67  
Old 09-29-2003, 07:55 PM
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Join Date: Sep 2003
Location: Miami, FL
Posts: 181
I GOT IT

Gentlemen,
I believe I got the solution to the problem on my benz, it may or may not be pertaining to your benz's. The problem I had was just as described, you start the car, it idles perferct for a few minutes, then the temp rises and and the miss/rough idle begins. Sometimes when driving and you initially step on the accelerator pedal, you feel a tad bit of hesitation for a few secs,when you are stationary (at a light or something) the car will also tend to shake due to the miss. After changing the plugs about 11.000 ago (platinum 4's). the Cap, Rotor, Ignition Wires (Quite Recent). I last week pulled out the plugs and each and every one of them was black ( I mean black). I wondered whether this was because they were Platinum 4s and they are not really recommended on the older benz's as I recently found out , or whether it was another issue. I changed the plugs to the regular Bosch Super's and didn't notice any difference. Today I pulled out the Idle control Valve and replaced it with a used one from a parts car, I drove the car round the block and sure enough, it was humming. It was music to my ears. I actually just got into the house from a drive, I just sat in the car listening to it hum. This may be one of the problems one of you guys is going through. But make sure you know it is the Idle Control Valve before you spend the $295.00 for the little sucker!! Yup that little sucker is expensive. if you know of any parts cars anywhere you might want to check them out prior. I figure the other parts that I changed needed to be changed anyway, except for the wires which I think were fine!!
I have an 83 380sel (Euro).
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  #68  
Old 09-29-2003, 11:07 PM
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Join Date: Jan 2001
Location: Tucson, Arizona
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Another solution to the list

Greetings,

Glad to hear that you solved your problem with the idle control valve. Did you happen to pull the Bosch plugs after running them for a hundred or so miles before changing out the idle control valve? Just curious to see if they would be black as well indicating either an over fueling problem or under aspirated which was your case. My plugs actually looked pretty darn clean after 11,000 miles with the exception of number one and six plugs which seemed to be tanted with a light brown instead of the usual grey deposits on the electrode ground. These were also the two cylinders least affected when pulling the wires off the plugs. Could be just a coincidence but the spark seemed hotter on all the rest when removed. I also noticed two spots inside the distributor cap on two cylinders that were more arched then the others, but didn't notate which cylinders they were. I think my problem may be solved with this new cap I purchased. I'll find out as soon as I get the lower cap cover as it shattered upon removal.

Glad to hear you're up and running, another success story. I do have to say that after cleaning up the inside corrosion of the OVP, that the car starts easy again and it even idles 200% better than it did. Don't know what it has in common with the idle but it worked.


Charles
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"Tell me and I will listen, Teach me and I will learn, Show me and I will accomplish, Involve me and I will succeed."
'84 300SD 256,000 Gold on Brown (Mileage Award)
'86 300E 246,000 Blue on Tan
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  #69  
Old 09-30-2003, 08:36 AM
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Join Date: Jan 2003
Location: Matthews, NC
Posts: 1,356
Can-Do

Usually the plug wires don't give much problems. It's the ends that breakdown on the Benz. On most cars, the wires have resistance built into them. Also, the plugs have resistance (usually indicated by an R in the plug number.) On the Benz, all the resistance needed is in the end which just screws onto the wire. The Ignition on the MB is designed to work this way. If resistance is added anywhere it's not supposed to be, the car runs bad. All platumn plugs I have seen have resistance in them so they don't work very well. On your car, the wires should be "solid wire" wires, the plugs should be "non resistor" and the plug ends should show about 5K ohms resistance. I use BP5ES NGK plugs in mine (84 500 SEL) The Bosch W9DC also work fine.
From your discription of the plugs and the cap, I suspect the plug wire ends are bad, or possibly the plugs. If you change the plugs, use either the bosch or NGK plugs with NO "R" in the number. I had a problem when I first got my car back together and running. I made a mistake when I needed a coil to dist wire and used a wire from a chevrolet which had resistance in it. The car ran perty good but had a rough idle which couldn't be adjusted out. After looking at the firing pattern on a scope and realizing something was wrong, I changed the coil wire and all the idle problems went away. Car also ran better at speed and got better gas mileage. Doing something in hast (the coil wire) usually will come back and bite you in the ....
Change the cap and check the wire ends with an ohm meter if possible.
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  #70  
Old 10-03-2003, 12:20 AM
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Join Date: Sep 2003
Location: Miami, FL
Posts: 181
What's the Latest

Can-Do , what is the latest, Howz it Running now, Let us know, looks like a whole bunch of folks who were on this thread have their cars running up to Par, we are waiting for you Buddy!!!
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**A few Hondas etc... etc... Not Worth Mentioning**
83 Euro W126 380 sel Money Pit (Sold)
91 W124 300e 2.6. (Sold) 3.0 Motor is Much better!!
93 BMW E34 Touring Wagon (Sold) Sweet Car!!
91 300e (Just 200k with Ease.)Best car ever ???(Sold)
90 420sel (Black with Tan Interior) Best car ever!!!!!!!
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  #71  
Old 10-03-2003, 10:14 PM
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Join Date: Jan 2001
Location: Tucson, Arizona
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As it was posted in my last thread

Greetings,

From all the threads I've read on my post, everyone doesn't have their car up and running to par yet. I believe several are still looking for more input and ideas to work them through the problems they are still having with their idle. I for one ordered several new connector ends to replace the remaining ones I didn't change out over a year ago, as well as a new lower suppressor cover as the old one broke as I loosened the distributor cap. No sense at this point to change out the cap until I recieve the lower housing that fits beneath it, so I'll wait till it arrives and do it all at once. As far as how it runs right now, it seems a lot smoother as I mentioned after cleaning the plugs and end connectors as well as cleaning the OVP and reinserting it. The idle isn't roughnow but has a miss in it when it idles and it seems somewhat sluggish when you step on the gas, but don't kick it down into the next lower gear. I still think the new cap and wire connector ends will pretty much solve my problems just by seeing the improvement I've gotten with what little I've done. Stay tuned though and I'll let you know for sure when I get the parts and get them installed.

Charles
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"Tell me and I will listen, Teach me and I will learn, Show me and I will accomplish, Involve me and I will succeed."
'84 300SD 256,000 Gold on Brown (Mileage Award)
'86 300E 246,000 Blue on Tan
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  #72  
Old 10-10-2003, 09:50 PM
seth9903
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My problem is solved too!!! (with crossed fingers and knocking feverishly on the nearest chunk of wood)

I don't want to jinx myself, but the rough idle at normal operating temperature appears to have been linked to one of the two minor updates that I just completed on my 1991 560 SEL:

new bosch spark plugs
new voltage regulator

The plugs were fouled with black carbon deposits, although the one closest to the driver (I don't know how they are numbered) had so much buildup that there was no gap, just gunk! The interesting thing here is that the car did not miss all the time. If the problem were just a fouled spark plug, then it seems like the car should have run badly all the time, as the condition of the spark plug firing end is not as dynamic as the temperature of the car. Can spark plugs lose their functionality as temperature goes up?

The old voltage regulator was VERY worn, with less than a centimeter and a centimeter and a half left on the brushes. I don' know how much that part is related directly to the miss problem, but I have seen in other posts that a voltage regulator ($17.95) can take care of problems such as:

rough idle once the car reaches normal operating temperature
hunting engine
a major nuisance (sp?)

SOOOO, I know that a car with 260k is likely to have other issues, and I have read here that the oxygen sensor, ignition coil, plug wires/ends, idle control valve, and fuel injectors are also prone to problems similar to those I just described. Are there any recommendations about which of those parts to replace and in what order, if I were to put about a hundred bucks a month into the car?I hate to just drive it and wait for things to break.
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  #73  
Old 10-21-2003, 12:17 AM
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Location: Tucson, Arizona
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After Fix Wrap Up

Greetings All,

Yes, it's been a small period of time since I last posted as well as had a chance to actually work on the Benz in question. Sorry, extremely long work hours and only one day off a week makes it tough to accomplish everything that needs to be done around the house going into the Fall season. Mind all of the posters this is only the second day out on this repaired vehicle so repairs will prove themselves over a several week period of time before I consider it resolved. In order to resolve my hesitation on acceleration and rough idle while at a stand still in the drive position, I went to the electrical system for an answer. I replaced all the spark plug connector ends as well as changed out the distributor cap to solve my problem. Strangely enough while changing out the distributor cap the number three spark plug wire broke the connector end off the cap because of corrosion. I can't say that this was the entirety of the problem but the engine now runs quite smoothly in all phases of it's spectrum. I am not saying it fixed the problem just yet but two days into the fix it seems to have made the difference thus far. Any fixes that other fellow posters have made could also be your solution, and I encourage all that have solved their rough idles to post so as to aid those that are seaking an answer as well as those will in the future have a post they can go to in order to have a starting point, and hopefully an ending point to their problem.


Thanks,


Charles

I will post you all in another couple weeks to give everyone an update.
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"Tell me and I will listen, Teach me and I will learn, Show me and I will accomplish, Involve me and I will succeed."
'84 300SD 256,000 Gold on Brown (Mileage Award)
'86 300E 246,000 Blue on Tan
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  #74  
Old 11-06-2003, 10:26 PM
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Location: Tucson, Arizona
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Three Week Update on Idle Problem Fix

Greetings all,

Just dropping a note in this post to let other posters that are seeking idle problem fixes to their 300E Mercedes that three weeks from the above repair and all is running great and no reoccurance of the problem has come upon me yet. I really don't expect it to either. Although a lot of folfs don't think that the OVP has anything to do with performance, it does, and it will also play havoc on idle speed and the antilock light on the dash. It generally isn't the only culprit to the problem as we now well know.

Charles
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"Tell me and I will listen, Teach me and I will learn, Show me and I will accomplish, Involve me and I will succeed."
'84 300SD 256,000 Gold on Brown (Mileage Award)
'86 300E 246,000 Blue on Tan
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  #75  
Old 11-07-2003, 10:16 AM
seth9903
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good idle then bad idle...then good

Just a note...
When I replaced the plugs and the voltage regulator on the 560 sel, the vehicle began to run well for a short while and then after a few days the idle problem came back. I looked under the hood and noticed that there was a blue halo around each of the plug wire connectors. BAD WIRES! I relplaced them. Now the rough idle was constant, up and down the rpm scale. This led me to believe that there was some other problem such as a bad injector or perhaps the ignition coil, etc. I spoke to my mechanic friend and he asked me if I had checked the plugs again, because one was probably fouled. The number eight plug was fouled, I replaced it, and the car runs like a dream.

It would appear that these cars, with oil burning through the valve guides, need to have constant attention to the plugs. I know that this was not the solution to other posts here, but I did also have to put in the plug wires and the voltage regulator...

Seth M
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