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Q: 4 days after dealership replaced headgasket I need a new transmission

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I was told my head gasket needed to be replaced, and to do it before my warranty ran out. Last week I had the dealer do the work along with bg fuel system cleaner. The same dlr has been the only one to work on my car. 4 days later I tried to drive from Sacramento to Tahoe. I only made it 45 miles. On a slight hill my car would only accelerate to 40mph. No indicator lights showed on my display. I talked to the dealer and we agreed I would turn around and try to drive 50miles to the dealer. On the way down the hill, the check engine light flashed and eventually stayed on. Upon inspection, they said one of the ignition coils went bad. They replaced it, and I was back on the road to tahoe. I made it about 5 miles farther than the first time. But again, my car seemed to lose speed and could only go 40mph. No indicator lights EVER came on. I turned around again and drove back to the dealer. They say it's a mystery, but I need a new transmission. I asked about MAP sensor too, was told no.

My car has 95000 miles.
My car has an automatic transmission.

A: Hello. The sequence of events and multiple ...

Hello. The sequence of events and multiple failures you are describing are unusual. To replace a head gasket at 95,000 miles is unusual, except in a circumstance where the engine was overheated at some point in its life. Because you are describing so many issues, before I get into detail and for your own protection and benefit going forward, I have to tell you that if a mechanic who is otherwise a stranger tells you that a part has to be replaced, you have to ask why and also ask for a specific diagnosis and test results (i.e., documentation or evidence).

Otherwise, there is a non-negligible probability that you are not going to get the best outcome - parts might be replaced or services performed that you do not need. So with regard to the head gasket, in order to fully understand the context here (and for you to fully understand, too) we would need to know why it was replaced.

You have mentioned that the mechanic encouraged you to do this work "before the warranty ran out." Yes, if the head gasket has in fact failed, that’s reasonable and prudent advice but they obviously knew it was work that they would be reimbursed for (they said it themselves) and so if you didn’t need a head gasket or it was cavalierly diagnosed, then obviously that is a problem. By the way, you should open the hood and be sure there is evidence that the gasket was actually changed out. Volkswagen Technical Services might not recommend a "fuel system cleaner." In fact, many vehicle manufacturers discourage these aftermarket gimmicks (there are a lot of them, cleaners, sealers, enhancers, you name it) which are more money makers than cleaners.

Broadly, if a fuel injector is so dirty that it needs to be "cleaned," the proper procedure is to remove the injector (preferably all of them) and they are send it out to specialized labs that use ultrasonic cleaning technologies to clean them. Furthermore, if the injector is dirty, the internal injector filter has to be replaced and those labs replace them. Filters are not cleanable with fuel system cleaner, particularly if there is solid particulate matter caught in the filter. That brings us to the Check Engine Light and the new coil.

If I understand your account correctly, that repair did not solve your issue and upon your return they newly announced, "congratulations, you need a new transmission!" and you need one to solve the mystery. Auto repair diagnostics are not always easy but there are some simple rules: if a mechanic seriously tells you that the malfunction your car is experiencing represents a mystery and consequently they are stumped, run for the exits. A car is fixed, unalterable collection of mechanical and electronic components that operate with SPECIFICITY. There is no mystery at all and there never will be. The human body is a definite mystery.if your doctor tells you, whew, you got me on that symptom, that’s understandable (happens all the time). But, no way on a car. Cars are much simpler and the number of "cells" is much smaller.

Based on your overall account, you appear to need a new mechanic. That mechanic will take it from the top, look for the head gasket, look at the present codes if any, and if your transmission is implicated, look at that, too. You might want to have another mechanic take a look at the car for you before moving forward with a repair. A certified professional from YourMechanic can come to your car’s location to diagnose the acceleration problem in order to have this corrected.

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