I'm going to keep it short and sweet. I need some advice.

I dropped my car off Tuesday the 9th at the mechanic for rough idle, MAF/Throttle Position/etc. DTC's. When I dropped it off, they quoted me $750. It's now been there for almost 2 weeks, they admitted they are in the same exact situation with the car, even after "repairing" part of the wiring harness. The car is has the same problems and the CEL is still on. I just called them and they said further diagnosis is needed which is going to mean more charges.

I feel like I shouldn't have to pay anything besides the diagnostic fee. Mind you this is the second time the car has been at this shop for this issue. The first time cost me $1000 and it didn't fix the issue. I've also spent $200 on Uber's getting to and from since my car went it.

What is fair here? I know they put man-hours into my car, but nothing has been fixed. How the hell should I have to pay anything if nothing has been fixed? And to pay even more for further diagnosis?

I asked them when is best for me to call their service manager, but I don't know what i'm going to say yet. I certainly believe I'm owed at least some kind of refund. Any advice?

1st, check the laws in your state! Refusing to pay could result in a "mechanic's lien", meaning they can keep the car to recover their costs. I am assuming this in an independent shop and not a Mercedes dealership. Did you sign anything giving them permission to work on your car? What does the fine print say?

You really haven't told us much about your problem for anyone to give advice. Maybe you can provide some answers.

1. What was wrong with the wiring harness for them to "fix" it?
2. What were the symptoms? Any DTCs?
3. What DTCs did you have?
4. When did the problem first start?
5. When does it happen? All the time?
6. What diagnostic tests did the shop perform?
7. Why do you think there was a problem with the throttle position sensor? The MAF? (Does your car use a MAF?)
8. What did they base the quote on?

A rough idle can be a lot of things: Bad coils, bad spark plugs, vacuum leak.

OK, I just re-read your other posting. My first suggestion above is to still check your state laws. If the $750 was to fix the wiring harness, and they fixed it, you may have a hard time not paying for that. I would say that if the car is drivable, take it to someone who knows MERCEDES (like the dealer) for a diagnosis. Find out what is wrong and then decide how to proceed with getting it fixed.

I never signed anything. The $750 was a quote for fixing the issue of rough idle and rough acceleration.

So, it was a verbal agreement? Or did they present you with anything in writing? How did they come up with $750?

Does Arizona have a state consumer advocate or office for consumer protection? You need to find out. Then present your question to that office. This forum is not the place to ask for legal advice.

There was no agreement whatsoever. I dropped the car off, they called me a few days later and said it's will be $750 to fix it. Now they still have the car and their "fix" didn't fix it.

I'm not asking for legal advice. I'm asking for regular advice. I'm asking what somebody else would do in my situation.

Under those conditions, if they said they would fix the car for $750, and they did not, then one would logically conclude that you owe them nothing. HOWEVER, you can't say this won't become a legal issue if they don't return you car without payment. Handing them the keys is implied consent for them to work on your car, and it becomes your word against theirs as to what was or was not agreed to. Do your homework about what protections you have AND what protections they have. They may NEED to have your agreement in writing or they may not. Your state may require a written estimate, or it may not. You state may limit how much a shop can exceed the estimate without notification, or it may not.

Your issue at this point is not a technical one, but potentially a legal one.

Logic rarely applies to established law.

you’ll have to pay for the diagnosis and wiring harness “fix”. They did attempt to fix it and put man hours in.


my suggestion to you, buy yourself a scanner from an auto parts store or Amazon. Read the code and post the trouble code here. That way we can all get an idea of what your working with.

i had a CEL on for MAF/MAP and one of my sensors was not bolted in all the way and an intake manifold gaskets was chewed up.

as for the rough idle… could be spark plugs/ignition coils if they are the originals. OR, the MAF/MAP sensors are bad/gummed up with oil. OR, your PCV system might not be working as it should, which would mean a new valve cover. I just replaced mine and it fixed a host of problems. I have a whole thread on it.

check to see if you have excessive crank case pressure if you pull the oil cap while running at idle and in park.

these are just some suggestions from what I’ve dealt with. But without the exact trouble code number we are shooting from the hip.


ant

Good advice. I would suggest not wasting money on a generic OBD scanner, but get one specifically for Mercedes. Generic scanners can give misleading results.

If I read it right you said first time you spent $1000 at this shop and 2nd time $750 for the same issue.
What was their reasoning that the $750 would fix the issue where $1000 work did not fix it? What did they verbally say that they missed the first time?
Did you go back and asked them to look at the issue since you already spent over $1750 there and the issue was still not fixed? And, when did you pick up the car 2nd time did you leave the shop with CEL and other issues?

Have to talk to the service manager for more info. Its possible there was an issue with the wiring harness that lead to other issues. I like to give people the benefit of the doubt they are acting in good faith to the best of there capabilities, until they give me a reason not to. Look at the itemized bill to see what exactly they charged for.

Not sure what wiring harness they replaced but ive seen Mercedes engine wiring harnesses cost $400-$750. If they used new Mercedes parts.