Hi acuratltrouble. Welcome to the forum. If it's the mechanic's fault, why did it run fine for three days? Every mechanic fears the "ever since" syndrome. That's where anything that goes wrong days or weeks after he touched the car is his fault. There is very little involved today in a tune-up compared to thirty years ago. That's not to say, however, the new problem couldn't be related to the recent service. First you need to find out what the cause of problem is before assigning blame. A new spark plug could have a cracked insulator. That's not really the mechanic's fault but it is something he will take care of. A vacuum hose could have been knocked off during the service. If the rubber is old and deteriorated, disturbing it while removing other parts could have loosened it and it took three days to become disconnected due to normal engine vibration. Again, this is something he will take care of but it's not fair to blame him for overlooking a hose that he didn't touch and wasn't causing a problem when he had the car. Too many people have the attitude "well, he SHOULD have seen it". That means he should have been psychic! We really aren't that good. :)
Your new problem falls into one of three categories. It could be totally unrelated to the recent service, it could be an unintended byproduct of the recent service, or it could be a result of the recent service. A reputable shop / mechanic will determine the cause of the problem and do everything possible to make it right because they want you to be happy and come back again, but they also have to look out for the business and not give away too much for free. It can be very hard for them to have to explain why the new problem is just that and it's something you'll have to pay for.
Next, if their work led to the new problem, reputable shops will apologize and fix it at their expense. New parts can be defective, and some less-expensive aftermarket parts just don't work as expected in some cars. In the words of one manufacturer's trainer, "we not only sell you new parts, we provide them pre-broken". When this is the case, most shops will not charge additional labor to replace a defective new part. They CAN legitimately charge if a new part is needed that wasn't previously installed.
If something was damaged or done incorrectly that led to the new problem, reputable shops will repair it at their expense and often do something extra for you such as offering a free oil change. The key is the cause of the problem has to be identified first. Even then, less-than-reputable shops can just as easily make up a story about why the new problem isn't their fault. Usually those shops are already well-known, but regardless, they are the ones that give the entire industry a bad name.
The first thing you should do is contact the shop that did the tune-up and explain what is happening. They will most likely offer to look at it as soon as possible. If they claim it is not their fault and it's going to be an expensive repair, the next thing would be to get a second opinion from a different shop. Most shops don't like to cut down their competitors because making a competitor look small doesn't make them look big. I'd suggest you don't even mention the name of the shop that did the tune-up. If that first one IS less than reputable, the second shop may be predisposed to looking extra hard for something to blame on them that really might not be deserved.
Monday, October 4th, 2010 AT 10:48 AM