Had to replace brakes and a full tune up. Not too bad! Great car, runs well with lots of power... till now. Check engine soon light has been coming on, so I have checked spark plugs etc. Loss of power on acceleration is awful. Disconnected the battery, but no difference. Not sure why?
Very fast, 210 horsepower and rear wheel drive.
I would love to keep it till gas prices get too high.
Great look and design for an older model vehicle.
Did the trouble start right after the tune-up? Perhaps something wasn't done correctly. Also, could you have clogged fuel injectors? Did it happen almost overnight, or did it get progressively worse until it became too noticeable to overlook? You checked for shorted/loose plug wires, loose spark plugs, weak coil, failed O2 sensor? It's common that if a sensor fails, the computer can reset to default values, prompting your check engine light to come on and also resulting in dramatic loss of performance and mileage. If not addressed, I've seen engines run so hot as to crack an exhaust manifold.
A tune up was done on this cougar about 8 months ago. I tried fuel injector fluid as well. I am not sure how to check the O2 sensors without paying for a computer diagnostic, which is so expensive. Thanks for the advice, I guess I will have to do something soon because a blown manifold would be bad!
I guess the first question is, who did the tune-up? I've had friends who paid a couple hundred dollars for a tune-up, but whatever the garage's definition of that was, it didn't include a distributor cap, plug wires, or spark plugs. Pull the plugs and confirm they were actually changed. Check the color of any deposits on the electrode. Heavy black soot is a sign it's getting too much gas; white is a sign it's running too lean; a normally operating cylinder should leave plug deposits that are light, creamy brown. The other simple thing, keep using the fuel injector cleaner, just one bottle probably won't reverse years of accumulation.
You might be able to check your O2 sensor yourself. For any older car, a Hayne's Manual is a good investment, and they explain how to check just about everything. This is just a kind of switch that tells your engine's computer how to adjust the performance. I'm a little out of my depth on these, but it's possible that you could check the resistance or voltage with a circuit tester, and the Hayne's Manual would give the tolerance values. Seems to me that on one of the other comments, there was somebody who did a good job of explaining how to test these O2 sensors, and had a similar problem as you.
Great advice, thanks very much. When the problem has been fixed I will post the solution!
Check your intake manifold. That's what happened when mine went out.
Might have a clogged catalytic converter, happened on my car (83 Olds)... cut it out and put a straight pipe in, noticed quite a bit of difference...
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