my mpg has dropped to about 20 and I don't know why. I have newer plugs, cap, rotor, fuel filter. I'm at about 90k on the engine. I did buy new tires and shorten my CAI to a short ram intake for easier filter cleaning but neither of those things would be killing my milage this much.

I got the car at 70k and got around 33mpg, in the last year it dropped to about 26mpg, and just on the last fillup it measured at 19.

I'm a bit lost as to where to look for a problem since it runs and sounds just fine. The ONLY possible symptom that I can put my finger on is that the passenger compartment heats up faster than a normal civic would when I start it up in the morning.

any clues?

 

Check your spark timing, if it's retarded you will get bad mileage. If you find it is out of spec, likely that's because the timing belt has stretched out-- it needs to be replaced.

 

I'll check that out this weekend. any possibility this could have something to do with a TDS sensor going bad? Mine threw a code last summer but I thought it was a bad connection in the wiring.

 

Did you clear the CEL code and now it has returned?

 

cleared it and it didn't return again. is it possible for the sensor to be ***** without throwing a code?

 

It's possible but, without some other evidence, it's risky to assume a problem with the sensor without the code repeating.

 

Sometimes the O2 sensor before theCat can be bad even though it doesn't throw out a code. Soyour engine can be running rich causing bad mileage.

 

update: Well thankfully the compression test was good. The plugs are pretty sooty though.

Checking the timing is beyond me without help or a good DIY. The instructions showed how to hook up the gun and press the on button but not how to figure anything out. It just so happens that might have been enough though. When I got the gun flashing it missed a beat about 1 out of 10 times. Now the question is whether that means the plug isn't firing or if it's somehow normal...

Any more advice? I'm starting to think dark thoughts of paying someone to work on it.

 

Sounds like the engine is misfiring. Take the distributor off and inspect the points inside the cap and the rotor. Look for corrosion and excessive wear. If so, clean or replace. You also might need new plug wires.

 

I was thinking that so I pulled a supposedly missfiring wire out of the socket on the cap with the engine running. I kept it close enough to arc to the cap and I didn't see any missed beats. Thats why I was suspecting the timing gun...

(I made damn sure not to ground myself while I was holding the wire )