huge mileage problem, getting worse, need help!

[ydeardorff]

OK, folks Im hoping you can help me figure out what the hell is going on.

I spent 2 years getting this car back on the road.

New used motor
New used trans
new axles
new axle seals
new lower control arms
New tie rods end
new torsion bar ends
new clutch
new pressure plate
new throw out bearing
new pilot bearing
new wheel bearings
new disks
new pads
new drums
new shoes
New composite headlights
new HID headlight system
new rotor
new dist cap
new wires
new plugs

After getting her one the road 208 USD
first tank of gas =57.8 mpg
second tank of gas 47.8 mpg
third tank of gas 33.3 mpg

What the heck? I attributed my first drop in mpg due ot me possibly getting used to the car and being abit heavier on the gas. After all this is a car you do have to wait for the car to catch up to the gas pedal not unlike the little Honda scooters in the 80's. But 33 mpg??? forget this!

The car runs like its new, and drives perfectly. No dragging brakes, everythings perfect except the uber mileage I'm supposed to be getting.

Can I get some help here on this? I know the timing is correct. I check ed it myself and jumpered the pins as per the manual. I set the timing myself, and triple checked it. I do know other geo's are faster and more powerful than mine. Did it possibly jump the timing?

I drive 100 mile a day round trip to work and back, this car is the only thing I have reliable left!

[Johnny Mullet]

First steps..............

Check for a clogged catalytic converter.

Perform a compression test on that "used" engine.

[ydeardorff]

As far as memory serves, I did a compression test about a year ago, and it was about 115 to 125 psi. per cylinder.
On long trips, it has smelled like coolant abit, but no evidence of it leaking anywhere, nor is it losing any that I can see.
I suppose Ill have to take it into a shop to have the cat checked, I don't know of any way to check it myself.
I found a cat on ebay for my car for 115 plus shipping, but hate to spend my money on something it may not be.
The exhaust flow off the tail pipe seems fine, but Ill get that checked, thank you.

The only problem I do note on the car is it reads 5 mph low on the speedo, and the gas gauge doesnt work, so I drive it like a motorcycle and just keep an eye on the mileage.
I read somewhere about a possible fuel leak only when driving under the drivers side? I may have to check for that as well. Just in case.

One thing noted while driving at high way speeds is the gas pedal seems to have no apparent use past half way. the engine doesnt respond at all to full throttle while going 50+.

And last bit of info, I only run super unleaded in the car.

[91Caprice9c1]

What's the model year and engine size?

These cars were designed (ie tuned) for economical fuel. Purchasing the more expensive stuff (which is more difficult to ignite) is making the combustion process less efficient than it could be. I recommend sticking with regular.

I would consider your compression numbers low. But that's only because after a rebuild on 3 cylinder engines I would see ~210 psi across the board. Maybe other metroeans have a better idea of where non-rebuilt motors tend to be.

This is a difficult post to answer because a lot of things can screw up fuel economy. A misfire, or crank no-start condition, as examples, are much easier to nail down and resolve. Backed up exhaust as mentioned, could be sensor related (o2 sensor, engine coolant temp sensor, throttle position, manifold absolute pressure, intake air temperature), low compression, leaky fuel injector, cam and ignition timing could be to blame.

Unfortunately, all of these things have test procedures and specifications and your ability to track down the problem is directly related to the equipment you have and how much time and effort you're willing to spend.

You can check cam timing by pulling the front cover off the motor and seeing that the marks are aligned, you can see if the injector is leaking with a modified actron fuel gauge and two hose pinch pliers, you can look for a excessive exhaust back-pressure with a good vacuum gauge connected at the brake booster hose while looking for a drop of greater than 5in.Hg. from idle at 3,000rpm. It all depends how far you want to go.

If it has been a while since some good basic maintenance has been done including an oil change, gear oil change and an ignition tune-up - they're not a bad thing to do.

Sorry about the length, just thinking out loud.

-Matt

[91Caprice9c1]

Originally Posted by ydeardorff

One thing noted while driving at high way speeds is the gas pedal seems to have no apparent use past half way. the engine doesnt respond at all to full throttle while going 50+.

I just saw this after posting. I would strongly look into an exhaust restriction/catalytic converter partially melted.

-Matt

[91Caprice9c1]

accidental repost.

[ydeardorff]

I just went out and grabbed a spare O2 sensor from a spare motor in my garage.
The pulled one out of the motor looked white on the tip.
The spare was a two wire, the pulled one was a 4 wire.
I fired up the car, and everything works fine, no CEL.

It a 1995 geo metro 1.0 cyl 5 speed trans.

There is plenty of exhaust pressure by checking with my hand at the exhaust tip.

No rattling on the exhaust internals can be noted.

Ill order a new exhaust system in the next couple of days.
along with a new O2 sensor.

Should I lok into checking the maf or tps sensor?
Any lil tricl to that?

Also the motor has just had a fresh oil change, air cleaner, oil filter, belts,... everything, even the gear oil is new.

[Woodie83]

Originally Posted by ydeardorff

As far as memory serves, I did a compression test about a year ago, and it was about 115 to 125 psi. per cylinder.

That's wore out dude. Factory manual says 200 new, 150 minimum. They'll actually run down to about 100, but not well. With the weather getting cold, you might find it hard to start in the next month or so.

Lose the high test gas, unless you've advanced the timing a bunch to make use of the extra octane, it's doing nothing for you.

[ydeardorff]

My numbers could be off, I do remember thinking the readings were good, based off the manual. Ill recheck them once I can find all the bits to my compression checker, and let you know.