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1999 c280
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22 Posts
Discussion Starter #1
Hey everyone,

So after following some members advice, I have been haggardly driving my c280 around town, with random surges, and sporadic rough idling, solved temporarily by restarting my car.

Its time to get something done about it, so im taking my car for a second opinion at a different shop tommorrow, and I need a rough idea on an average cost for this fix. Codes read random misfires and misfires on particular cylinders.

1999 c280 (12 plugs)

I already replaced all the spark plugs with Bosch plugs, and the MAF. The recommendations that I have gotten from other users is to:

a) replace all the wires / wiring harness
b) replace coils
c) both

Anyone have a rough estimate on how much this would cost?

I love this car, I would just hate to sink 2-3k on this and still have the issue. That combined with the sagging headliner...:eek:

Anyway, thanks for the help guys. Ill post the quote for anyone else interested
 

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1999 c280
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22 Posts
Discussion Starter #3 (Edited)
Funny that you say that, I was worried about DIY because I dont have a lot of experience.

Luckily, my girlfriends brother in law was a military mechanic and knows a bit about the job on a benz, he said he will help me out with it on sunday.

Now I have a cart at autohausAZ with a wire set (12 wires), and 6 coils. I'm trying to find a DIY guide somewhere just in case its more confusing than he anticipates.

Any recommendations? Think I should go ahead and just replace all the coils? Im at ~135k miles, second owner.

Edit: Too late :) picked up 6 coils for 500 w/ priority mail, going to wait on the wires as I heard they were in good shape from the shop. Fingers crossed.
 

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'99 2.3L Kompressor
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1,944 Posts
Since it is a 99, I doubt your problem is a wiring harness problem (spark plug wires could still be suspect though).

Before you go buying stuff, why don't you go to your nearby chain auto store and ask them to pull the codes for you for free? That might save you from buying stuff you don't need.
 

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1999 c280
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22 Posts
Discussion Starter #5
Thanks for the input, especially on the harness.

My thought process in targeting the coils+wires actually revolved around some codes which I had pulled at a local shop about a month and a half ago. The issue is exactly the same and was never resolved, so I (maybe incorrectly) am assuming the codes are still the same.

I forget the exact codes, but they were misfires on particular cylinders, and the code that said multiple engine misfires.

Based on that, the shop recommended that we start with plugs, because they were the least expensive to replace.

After replacing the plugs, the issue was still there, and they explained that in their mind the next step would be coils and/or wires.

Based on that, I just ordered coils and will be replacing those, and if that doesn't work, then I am moving to the wires. The reason for going with coils first, is that the shop mentioned that the wires looked great when they were replacing the plugs, and my personal friend who is helping me do the work, mentioned that he suspects the coils initially as well.

Do you think there is anything else in particular that would be throwing those codes? I really hope that we don't replace the coils and wires and the issue is still not resolved :eek:
 

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'99 2.3L Kompressor
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1,944 Posts
Your progressing is good but I doubt all of the coils went bad. You should have been able to get codes that indicated which cylinder(s) was misfiring and then swapped a pair of coils to see if the misfire moved to the new location of the suspect coil. $500 on coils is throwing a lot of money at the dart board.
 

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1999 c280
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22 Posts
Discussion Starter #8
Hey everyone,

Sorry for digging up this old topic, just realized I never came back to give you guys an update.

I replaced all the coils, but not the wires yet, and the issue is still happening. When I was replacing the coils, the wires looked fine.

I need to pass inspection by the end of the month so this CEL is now starting to get frustrating :mad:

Next steps? Either replace the wires or give up and take it back to the shop...or buy a new whip :confused:
 

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2000 C230 Kompressor Special Edition
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1,173 Posts
You need to find an Indy with the star diagnostic computer. Should be able to pinpoint your problems. Wiring harness on 1999 was not defective type like on older cars. Have you ever replaced the MAF?

Your spending a lot of money, best to go ahead and get the diagnosis.
 

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1999 c280
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22 Posts
Discussion Starter #10 (Edited)
Yes, the very first thing I did was replace the MAF.

So far I have replaced:

MAF
Spark plugs
Ignition coil packs


Thank you so much for the response/feedback
 

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1999 C280, 2000 C280, 2000 C230K,2011 C300
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660 Posts
Save those coils. There is probably nothing wrong with them. You really didn't need to buy 6 of them. You could of bought just one and moved it around to see if there was a faulty one. I would have changed wires before coils.

There are bum MAF sensors around also, particularly on ebay. Hopefully you got it from AutohausAZ.
 

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1995 C220
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2,800 Posts
The thing is, wires can look fantastic, but if they have built up too much resistance over time, doesnt matter what they look like, they will need to be replaced. Not sure what the numbers are but a coil wire is supposed to have a certain amount of resistance per inch/foot whatever you measure it by. If he didnt check it with an ohm meter then he doesnt know if the wires are good or not.
 

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1999 c280
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22 Posts
Discussion Starter #13
Thanks for the feedback guys.

All of the parts I installed were from autohaus, OEM.

I figured I would replace the coils because they were all original, and I thought while i was in there doing it, I might as well just replace them all.

So do you guys think now that I have replaced the plugs and coils, a trip to an indy for a diag might be able to provide more info? Last time I looked at the codes it was just random misfires on particular cylinders and then overall random misfires. All they could tell me is "It could be the wires, coils, or plugs".

After they replaced my plugs they even said they didnt think it was worth me continually chasing the issue, and that I should get a new car. I didnt accept that, so I did the coils myself.

I would definitely be down to do the wires if i had more guidance in regards to if it would actually fix the issue though. I dont know how much of a choice i really have
 

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1999 C280, 2000 C280, 2000 C230K,2011 C300
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660 Posts
New wires fall under the category of "New things that cars like".

Cars "like" new filters, plugs, wires, cap and rotors, fluids, etc.

Having said that, you don't want to be replacing things willy nilly. That is one thing about Mercedes OEM parts. They usually last a LONG time.

Time for you to find a better tech or go to a dealer.
 

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1999 C280, 2000 C280, 2000 C230K,2011 C300
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660 Posts
Wires are not technically difficult just a little time consuming with access and you want to be careful with your new wires. The ones closest to the firewall are tougher. Hopefully the OEM wires are the style that have a rim that you can catch with a wrench(13mm?) to pry them off. You have the advantage in that you will probably not reuse the old wires so no harm in mangling them.

Some thread showed looping some rope on the sparkplug end of the wire and pulling them off. Never seen that but seems like it would work.
 

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1999 C280 210k miles
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200 Posts
Post the codes!!! Hard to help without some detail. The Bentley Manual has a nice section that gives step by step process for working each code and what component is the cause. I'll be happy to help if I can.
 

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1999 c280
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22 Posts
Discussion Starter #18
Thanks everyone,

Im thinking about just ordering the wires, but i know the smart choice would be to go to an indi dealership and have them do a diag before i drop any more money. The problem is, the place i want to take it is an hour away and closed on weekends, and I have school and work all week :/

I will try to at least drop by an autozone to get the codes, will those codes be detailed enough or does it need to be a STAR diagnostic?

Also, what would you guys do? My inspection is up @ the end of the month and I have a 5 day window, worse case scenario i guess ill be driving stealth. Would you just go for it and order the wires (everyone keeps saying it has to be the wires at this point), or would you wait for a legit diag?

Thanks again, i love this community.

Edit: A set of wires is $134, the Indi wants $80 for a diag, not sure if that has any weight on the decision making process
 
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