Major loss in MPG

[nbleak21]

Originally Posted by streamfisher

One other thing that I have noticed is the car sort of surging during acceleration. Sort of like I am pumping the throttle even though I'm not. I have wondered if it could be a sensor of some kind.

Surging or stumbling during acceleration could be an ignition timing issue: check spark plugs, wires, cap and button, and verify distributor timing.

[streamfisher]

I did some testing on different sensors on Saturday and the only thing I found for sure was a broken wire going into the distributor. I soldered a new piece in there but this morning it stilled was surging. I have changed plugs, wires, fuel filter, and air cleaner all within the last six months. The cap and rotor have no carbon tracks, pitting, cracks or scoring at all so I haven't bothered to change them yet. I don't have a vacuum gauge but I want to get one.

[user removed]

My guess (and it's only a guess) would be the oxygen sensor is on it's last leg. Even without a CEL oxygen sensors can cause that kind of drop in mileage when they get old and lazy (slow to respond). This is assuming it has not been recently replaced. They can die much earlier if they are contaminated, particularly with silicone.

regards
Mech

[streamfisher]

Yeah, that was one of the sensors I tested and the resistance reading was about 16 and the specs said top number should be like 13 or 14 ohms. So I'm thinking I should maybe replace that and see what happens.

[Rusty94cx]

Unplug it you'll have a check engine light on but see if I goes away.

[streamfisher]

I will have to try that when I get home. Right now I am up in Washington taking some pesticide applicator training for my job. Thanks for all the ideas and replies!

[streamfisher]

Well I just tried unplugging the O2 sensor but that didn't seem to make much difference that I could tell. Car still had a surge to it. Any more ideas?

[freewheeling]

I had a surging and a low mpg problem with my car it turned out to be a plugged up catalytic converter.
EZ test if you have an engine vacuum/pressure gauge. Drill two 1/4 in. holes in the exhaust pipe one before and one after the catalytic converter, start engine, use the pressure gauge measure exhaust pressure before and after cat. If it's high going into the cat and low coming out your cat is plugged up and needs replaced. There will always be a minor pressure difference you will be looking for a major difference. Also you will need a way to plug the holes that you drilled, think of that before doing it.

[Rusty94cx]

You don't need to drill any holes hook op a vacuum gauge it'll tell you if you have a plugged cat. Strong vac that steadily drops If I remember correctly. Google and a vacuum gauge are your friends.

[thomason2wheels]

Originally Posted by F8L

Surging doesn't sound normal. Could it be a vacuum or fuel delivery issue?

Sounds like a vacuum issue...is the idle faster than normal, if so that would be what id look for first. You can spray wd 40 around intake gasket flanges with the engine running. If the idle slows and smoothes up, you found your leak