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Old 02-17-2011, 10:03 PM   #1 (permalink)
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Mileage drop of 21 MPG - need mechanical advice

Hey guys, I took my car into the shop since my car seemed to be acting funny.
The car has no power and dropped in mileage by over 21 MPG within the last few months.
The car has had a basic tune up - wires, plugs, new oil, etc, yet nothing has changed. The guys at the shop managed to ' accidentally' break my coil and the car would not start. I had to buy a new one at four times the cost and pay them over a hundred dollars for the labor ( or get the car towed home ).
They said that the drop in mileage was due to a worn coil, but now that I have a new coil, the car still has times when it just turns over without starting, and there is no change in mileage.
I took the car in because I feared that something else was wrong with the car, and wanted a complete diagnostic check. My check engine light came on every now and then, my speedometer worked, but at other times will not, and the car suddenly decided to not start one day- it turns over but won't start.
They couldn't get the check engine light to come on so i didn't get the code.
I had them run a compression check and they said the car is normal, but I just wanted a second opinion on what to do next.
The transmission is supposedly fine, because it is not slipping ( its an auto ), but the car is extremely slow and revs really high and just creeps along at 45 when it should be doing 65.

Just wondering what you guys would advise me to check for next.

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Old 02-17-2011, 10:07 PM   #2 (permalink)
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I guess I should mention what kind of car this is ;-)

1993 Honda Civic DX 1.5 L automatic.
Less than 130,000 miles.

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Old 02-17-2011, 11:00 PM   #3 (permalink)
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Bite the bullet, and take it to your Honda dealer for their scope and computer diagnostics. I'd have absolutely no faith in a shop that broke your coil and then charged you to fix what they broke.

There are too many possibilities in a 17 yo car w/>100,000 miles. They boil down to air, spark, and fuel, but there are lots of permutations like vacuum leaks, valve timing, and more. So far, all you've mentioned checking are spark and compression.

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Old 02-18-2011, 12:49 PM   #4 (permalink)
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In your case i believe your o2 sensor is the mess up your MPG. Change that then you have your MPG back to your original
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Old 02-18-2011, 03:40 PM   #5 (permalink)
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Lots of potential causes and dealers are not well versed in diagnostic repairs on 18 year old cars. They seldom see anything over 10 years age. Most of what they do these days is warranty, maintenance, inspections, and brakes.

Some easy tests.

Can you push the car in neutral with the brake off. If not you may have some sticking brake calipers, which would also show some signs of heat at the wheel where the bad caliper or wheel cylinder was located.

Your mileage change is not clear to me. How many MPG were you getting before and after the cnage occured? If the difference is 21 MPG then there is something dramatically wrong like jumped timing, or a stuck fuel pressure regulator.

If the compression test OK, then I would test fuel pressure to see if the regulator is functioning properly. Even a bad O2 sensor would not cause that dramatic a drop in fuel mileage.

Being a Honda, there are probably independent repair shops in your location that are much more familiar with your car than even a factory trained dealer mechanic, that might not work on an 18 year old car more than once or twice a year, if even that much.

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Old 02-18-2011, 07:56 PM   #6 (permalink)
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Being a Honda of that vintage and style, I would swag, you need a new distributor.
They are not cheap.
I have run into many cars like yours with similar issues that had a bad distributor and it's erratic operation is what caused problems.

But you should find a competent shop to help you. As was stated, a shop that charges you to repair something they broke, is not a shop to do business with.

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Old 02-18-2011, 08:29 PM   #7 (permalink)
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Check the fuel pump pressure. Also check if fuel pump is pumping enough volume. You may have a restriction in the tank. If so you may be able to back blow the fuel line with air.

Try asking your question here.

Honda | Acura Research, Reviews, Performance Parts, Owners - Honda-Tech.com

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Old 02-18-2011, 08:35 PM   #8 (permalink)
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Definately don't go back to the shop you had it at. Bad vibes there.

The tranny behavior seems very concerning to me. High revs without acceleration generally means it's slipping. Are there certain gears that slip and others that don't? All gears slipping? It may be worn clutches, a failing pump, or clogged filter/valve body... Try taking it to a shop that specializes in either Hondas or transmissions.

My brother owns a transmission repair shop and has mentioned that Honda's 90s era autos provide regular work for him. Those and Jeep Cherokees.

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Old 02-18-2011, 08:44 PM   #9 (permalink)
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don't forget in a car this old it could very well be the PCM as well. The best thing to do is get it to a good service shop and hooked up to a good scanning suite. I halfway competent mechanic with a good scanning suite, not just a scanner, can trouble shoot just about anything wrong with a car. Be aware it is not cheap, but really worth it.

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Old 02-18-2011, 10:04 PM   #10 (permalink)
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why exactly did you pay them to fix it? pretty sure if a shop damages your car they are liable

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