Sudden plummet in FE and nothing seems to fix it

[rvanengen]

Check to see if your parking brakes are dragging...if you walk by your rear wheels after driving, are they bleeding a lot of heat? Happened on my wife's car recently...

If you can get a good tool hooked up (SG, etc) check to see if the coolant temp sensor is reading correctly, and not in cold start temp mode...

Oh...and check your catalytic....

[brucepick]

Check your battery too.
Insufficient voltage or current capability will semi-cripple the engine management electronics.
If you have a voltage gauge of course it's easy - but most cars don't.

Best way in my opinion is to run a pair of wires from battery terminals back to the passenger compartment and hook em up to a multitester or voltmeter. Drive around with the meter where you can see it. Should be about 13.5- 14.8 when driving.

My son's Hyundai had a drop in mpg. We weren't aware the battery was not up to snuff. Finally the battery died and wouldn't start the car. After installing a new battery the mpg's went up again.

[Hateful]

Originally Posted by Hateful

I'd look at the electrical components; Spark plugs, alternator belt, battery connections. weak spark doesn't burn the fuel as well.

Maybe a new muffler if you haven't had it replaced before.

think we're going in circles here

[GasSavers_bobski]

Well, if the computer's throwing error codes for the cat, definitely check it out. I'm pretty sure junk yards are prohibited from selling used cats, so you probably won't have any luck with a cheap fix.
I would also jack the car up and check that each wheel can spin freely when it should... Dragging brakes can really screw up your fuel economy.

[txe5502]

OK, I checked the engine vacuum today, it is 20Hg, there seems to be no exhaust system problems. Now as far as the parking brake dragging, that simply isn't possible, I actually have to put blocks under my wheels because I used to pull the parking brake so hard, and I snapped the cable (parking brake doesn't work)

[GasSavers_bobski]

Originally Posted by txe5502

as far as the parking brake dragging

It doesn't necessarily have anything to do with the parking brake. Not long ago, my CRX had a worn caliper slider which let one of the front brake calipers kinda shift at an angle to the brake rotor, making the pads constantly drag on the rotor. Like I said, jack the car up and make sure the wheels can spin freely.

[txe5502]

Oh! I didn't think of that! That's right, my grandfather's Ford Escort caught on fire a few months ago because the front left brake caliper was dragging and it got so hot that the front hubcap caught on fire and melted off! I will check this as soon as possible.

I know it is not the back left one though, because I just replaced that brake caliper as it was leaking brake fluid. But it COULD be any of the others. Thanks for the info!

[VetteOwner]

did your weather suddenly change? around here ti took a nosedive same with my fe... tank before last 29mpg, this tank 24mpg...driven the same, same distance, i think part of it has to do with the cold weather and part due to i filled it way up this time...

[8307c4]

Probably in the spark, time to replace and use:

- Double platinum spark plugs.
- At least 8mm thick spark plug wires (10mm is even better, Taylor mfg's some).
- A high performance cap and rotor.

Why this isn't standard on all new cars, how they figure those 7mm wires and crappy parts to conduct enough voltage to burn the fuel through...

[GasSavers_bobski]

Originally Posted by 8307c4

- At least 8mm thick spark plug wires (10mm is even better, Taylor mfg's some).
- A high performance cap and rotor.

Why this isn't standard on all new cars[?]

Because most new cars use direct ignition as txe said his car does. With direct ignition, each spark plug has it's own dedicated ignition coil bolted to the head directly over the plug. Distributor caps, rotors and wires are meant to direct the high voltage pulse from one ignition coil to one of several sparkplugs at the proper time... If you have a coil for each plug, there's no need for a distributor. If the coils are bolted to the cylinder head, you only need a wire long enough to reach the plug - about 2-3 inches generally. The "wire" is part of the ignition coil housing.

Putting aside the fact that it doesn't apply to this situation, unless the OE parts are really poor quality, or the ones you are replacing are shot, you won't see much performance gain from aftermarket wires. You might see a reduction in radio noise, but I challenge you to find a dyno run where somebody installed new OE wires and then swapped them out for aftermarket wires and saw a performance gain. Same goes for caps and rotors... There just isn't much that can be done technology-wise to improve these things.
If you want to improve ignition system performance, get a new cap, rotor and wires (not necessarily aftermarket), a high performance drop-in ignition coil and fresh plugs. The best performing plugs will vary from car to car... In my experience, Hondas seem to perform better with plain old NGK plugs than Bosch platinums.