At the advice of someone at a local auto parts shop, I poured a bottle of fuel injector cleaner into my gas tank. This happened around the same time that I had a brake job done and rotated my tires.
Within a week, I noticed that my engine is performing poorly. It downshifts to climb small hills at freeway speed. Also, the car is getting very poor gas mileage. The car used to be able to get 400 miles on a single tank of gas and now I'm lucky if I can get 300, so there is a big reduction in gas mileage.
I took the car in to a shop. I paid them almost $100 to tell me that the only problem they can see is that the tires are a little bit off-round. I doubt that the tires not being perfect could be causing the problem, but there is a little bit of noise and vibration from the tires.
On the other hand, a technician at a shop I previously visited before this problem told me that he recommends a fuel induction service to restore the cars gas mileage and horsepower.
What can I do to make my car run better again? It seems like something happened right around the time that I used the fuel injector cleaner product, but perhaps my brakes or tires have something to do with it.
I did notice a gradual drop-off in fuel economy over the previous two years, but it just took a total nosedive last week.
Update: The car is a 2003 Acura 3.2TL. I'll have to look into the brand of the fuel injector cleaner.
Also, Bob Cross asked about if the car's mileage was dropping before I had this problem. Yes, it was dropping ever so slightly over the course of a few years, but it was right at the time that I put in the fuel injector cleaner that the fuel economy went way down. The car has an EPA reported highway fuel economy of 27 MPG. I drove about 230 miles last weekend at a speed of about 75 MPH and had to put in 11 gallons to refuel it. I calculated the fuel economy to be less than 21 MPG.
All I know to say is that it seems as if the car is just "working harder" to maintain highway speed.
New Information: I received a call from the service shop where the car is being examined. The tech tells me that he drove the car down the street next to the shop (not going at highway speeds where I experienced serious problems) and it seemed to run fine for him. He says that he connected the car to various diagnostic machines and there was no indication of any fault in the car. However, he says that upon checking the spark plugs, he discovered that the plugs have heavy carbon build-up, so he recommends replacing the spark plugs and performing a fuel induction service. Also, he says that the plugs in the car (which were installed several months ago) are iridium plugs and that the stock plugs would be double-platinum.
