Hi, first off I would like to thank everyone who uses this forum for the info provided here, it has been appreciated. I recently bought a 1994 C280 which I totally enjoy driving, and cannot find some of the info I would like to on it.

I took my car to Aamco locally and they retreived 9, yes NINE, OBD II codes from the car. The tech said that they all seemed to be from a misfire in cylinders 2 and 5 so that left 7 emissions related codes. Here is my plan of action to remedy this situation:

1) Have fuel injectors cleaned, most places have told me they use a 3 step chemical process for ~$60. If this does not work then....

2) Tune-up ($400) OR there is a reccommended shop here in town that will examine the plugs, wires, coils, and anything else which could cause this problem and fix only that at labor and parts cost which specializes in MB cars.

Chances are that I will wind up doing both since the first step, IMHO, will not remedy this problem....but you never know.

I have not had the dreaded wiring harness issue yet nor do I know if it has already been replaced. This brings me to my only remaining issue with the car. When I turn my headlights on the right side turn lamps, both front and rear, are steadily on. During day time driving the turn signals both work fine. I read a thread here and replied then noticed it was almost 6 years old, talking about intermittent turn signal and wiper malfunctions being due to a faulty combination relay switch. Could this be the culprit here as well?

If any of you have a better plan of action or suggestions/concerns please feel free to voice them.

Thanks to all who read this post and much more thanks to those who take the time to respond!!

--Graig--

where are you? are the misfires all the time? if so i have seen the 280's develop coil issues, i would check the plugs if needed and replace the three ignition coils, one coil goes to two cylinders. my opinion on fuel injection cleaning is it is just a sales tool, i have personally never seen a real benefit from it.

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1967 250 S
1967 280SE
1968 250S
1971 280 SE
1973 220
1974 280 S
1975 450 SEL
1976 220 D
1979 300SD
1983 300 SD
1985 230 TE euro
1986 280SL
1986 500 SEL euro
1986 190E 2.3
1990 300 SE
2003 C230 K
2004 C230 K
1987 560SEL
1987 300SDL now in canada
2005 C230
1998 C43 AMG Sold to DON
1993 190E 2.6
300TD Former daily driver Totaled
current:
R320 CDI
Ram 2500 Cummins

Welcome to the Mercedes family. How many miles on the C280? I would personally not have the fuel injectors cleaned. I would recommend going to the auto parts store and buying Techron by Chevron (about $8) gas treatment instead. Then, fill with premium fuel (as always) and it should clean any deposits on your injectors after a spirited interstate drive.

On the tune-up items I would encourage you to do them yourself. The coil packs are about $60 each (you have 3). These are easy to replace. The wireset is about $60ish for your car as well. You will almost always pay 3x as much at a shop with labor. These are easy things to do especially if you have a great forum like this...

Your wiring harness is very expensive for some reason. $1000++ There are several part #'s in the system, it would help to have the last 7 of the VIN. I would gently peel back some of the insulation and inspect for cracking. Good chance your has been replaced especially if you are well over 100K miles. On a low mile car, just no easy way to tell without a part # or visual inspection.

On the turn signals, the blinkers don't blink when the headlights are on? Has it always done this? Try a fresh set of bulbs all the way around on the blinkers (they are cheap). You could have a bulb issue, or a combo switch issue (blinker stalk on the column). It's easy to replace if you have the right tools (i just did one last week). Your part will cost about $121 ish. Airbag and steering wheel must come off to replace this switch as well as the lower dash. Took me about 1.5-2 hours tops. A shop would probably charge $300-450+ for this job.

Or, you may have a bad headlight switch. But, I doubt that. Start with the bulbs, pull each out and inspect the sockets. I say start with new bulbs because you may have the wrong one(s) in there to start with and again they are cheap.

Keep us updated and send along some pics of the C280. I had a '99 C280, and it was a great little car... Enjoy...

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For Now:
1992 Mercedes Benz 500SL
1998 BMW 528i
2003 Honda Element
2002 CBR600F4i
1977 Coachmen Motor Home

WHo knows how long those codes were there. Wait a week and have them reread, or just build a reader yourself for $20 and read them next weekend.

Misfires on 2 and 5 eh. If I recall, they are both on the same coil so its likely you have either a bad coil, bad insulator/plug wire, or a shorting wire feeding to the coil. Do step 2 first. Take nissan's advice regarding the injectors - feed em some cleaner and focus on the wiring. Check to make sure your harness has been replaced. Do a search on wiring harness and you should get plenty of hits. Also look at the wiring bundles under the hood. DO they look like they have been opened and retaped? MB bundles had a cloth tape cover that is continuous - no breaks. Most repaired areas would be the wires at the injectors and for the coil leads. These bundles would be bent back for normal servicing and are subject to insulation flex/cracking in the original wires. My car had these 18 wires (12 to the injectors, 6 to the coils) rewired. You will have to remove the nice wire tray cover along the cylinder head cover.

Did you get maintenance records for the car? Perhaps contact the nearest dealer and see if you can get a maintenance history for the car (if it was dealer serviced).


I recall one of the esteemed members here giving a quick method to evaluate the resistence of the coils to determine if they are bad.

As to your era car - Notorious wire insulation issues. I have a similar but not identical problem with the running lights/turn lights. Its likley part of the harness for the front running/headlights somewhere in the drivers side of the engine compartment has some bad insulation/faults in it. Have not taken the time to track that issue down on my '94 yet.


How is your coolant temperature in traffic? I found bad wires to my auxilliary fans for the radiator shot as well (they were repaired by the PO with Nomex 14/2).


Just work through the items methodically and you will be fine. Keep asking questions here to avoid throwing parts at the problems.

Good luck

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Brian G.

1994 E320 Wagon with many warts SOLD
1995 E320 Wagon with a beauty mark or two FOR SALE

The posters who posted before me seem more knowledgeable then me on the issues. I have a W202 and would just add - make sure your battery is in good shape - the W203 cars are more susceptible to codes and malfunctions with a weakened battery then a W202, but with all those codes thrown verify a strong battery. Also- get the actual code numbers thrown and google then to know exactly what they all show.

Change the plug connector/resistors under each of the 3 coils and install Bosch F8DC4 plugs..clear codes and drive it.
These are notorious for your condition. Us Search for verification

http://catalog.worldpac.com/mercedesshop/sophio/quote.jsp?clientid=catalog.mercedesshop&cookieid=2AO123CS42AW0N0IYF&baseurl=http://catalog.peachparts.com/&partner=mercedesshop&year=1994&product=F1010-84561&application=000357354

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A Dalton