But, I do need help. The temp guage was spiking on my '94 acura legend, a car I dearly love. Took it to the dealer who has mainatined it for 14 years. They said the head gasket was blown and thermostat stuck. They replaced the head gasket and ECT temp switch and knock sensors, hoses, and heater valve. The cost was $3100. Five days after I got the car back (they had it two weeks) the engine light came on and the engine smelled like it was burning but there was no smoke. I towed the car back to the dealer. Now they are telling me the PCM/ECU (electrical control unit and power control module - one in the same) must be replaced to the tune of $1200. The car was running like a top until they did the extensive engine work. I have never missed an oil change or scheduled maintenance. I have lost my faith in the dealer. Don’t trust them and feel like I’m being taken advantage of. The car has 167K miles on it. Did I mention that I love this car? Any thoughts?
I won’t speculate as to whether the dealer has any responsibility for the demise of your ECU. I am concerned that the problem might be wiring rather than the ECU, or that, if the ECU has failed, the failure may have been caused by a wiring problem, but the dealer will not want to spend the time to eliminate that possibility until they have sold you a new ECU. Their procedure will be - put on the new ECU, if it still does not work, troubleshoot the wiring, but the new ECU stays on.
Just make sure that they guarantee the ECU so that if the new one fails two weeks later due to a chafed wire that shorts out again, the dealer makes it right.
I would encourage you to look in to a junk yard ECU. The dealer won’t guarantee it, but it should cost a LOT less. If you can go that route, specifically request that the dealer examine the wires and connections around the engine looking for damaged insulation.
P.S. I am disappointed. With that subject line, I was expecting a self-effacing funny story.
Find an independent shop for 2nd opinion. $3100 is crazy for a 14 year vehicle to repair something and get socked with another $1200.
Independent shops with a decent mechanic (they exist, ask) will make car ownership pleasant and significantly better on the wallet. Acura dealers are nothing more than overpriced Honda dealers. And Honda’s are very common cars that any mechanic knows how to work on due to sheer volume of them. If you are more comfortable with a dealer, nearly all Honda dealers do non-warranty Acura work.
Well the OP is seemingly willing to throw $4400 at a car that is maybe worth $3k. That has to be worth something 
Andrew said it perfectly…you should find a reputable independent shop. Ask your friends and coworkers who they patronize and what their experiences have been.
As to the specifics, if you thermostat was stuck and your engine temp spiking, a blown headgasket would not be an unreasonable result. Since the car is 14 years old and high mileage, it is entirely possible that the rest needed doing, although if the knock sensors were bad it should have shown up as a check engine light (CEL) even before the engine overheated. I’m wondering, frankly, if they damaged them replacing the head gasket.
By the way, it sounds like you may have had some serious, possibly repeated, overheating. Once that happens with an older, high mileage vehicle, it may be time to start considering at what point you want to “give up the ghost”. You may want to start researching the new offerings.
That PCM/ECU could have caused the overheating. I’m happy that they foundthe underlying cause but the money is always tough to lose.