bad gas mileage (~12 mpg/over 20 liters/100km)

[silky]

I think my mileage sucks, but why?

btw it's a 1998 exploder with 90,x.. miles on it.

I have looked and there are no exhaust leaks. I inspected a couple of the spark plugs and they look good (they have a grey colour to them which from my research points to a good motor). I replaced the air filter recently and change the oil regularly. I am about to head out and pick up a new fuel filter, thermostat and belt.

2 things I have noticed:

1) I have a sticky throttle cable. Sometimes when you step on the gas from idle it doesn't want to go. You have to give it a hard shove before it will rev the engine. When opening the throttle from the engine bay there is a noticeable stickyness at the throttle body.

2) I have that problem with the driveshaft that causes the clunking when comming to a stop. I forget what it's called, binding slip yolk?

would these cause noticeable reductions in fuel mileage?

any ideas would be appreciated!

thanks,
John

p.s. that 12 mpg is about 70% city, 30% highway. As a reference I was once able to get 600km (~360 miles) out of a tank but that was all highway cruising. And I know these vehicle are not fuel savers but in these days of $1.15 a liter or $4.40 gallons, every bit helps!

 

[silky]

bump

 

[tmcphail]

02 sensors could be the culprit. We sell the OEM ones if needed.

 

[yogi_pahl]

Do you have a CEL light? As far as the sticky throttle take the cable off the throttle body and make sure its the throttle body and not the cable. If it is the body the a lil carb cleaner should help that.

 

[aldive]

First, you need to solve that sticking throttle. Take the cable off of the TB and see if the TB moves freely. I would throughly clean the TB.

Next, clean the MAF.

Take a scanner and check the function of the O2 sensors.

How is the tire air pressure?

How is the PCV valve?

 

[silky]

I seem to have solved the sticky throttle problem but it's hard to tell. I don't drive it that much but after spraying the throttle spring with lube it seems better. I did notice a lot of black crap in the tb so over the weekend I am going to clean it up.

The pcv valve I guess I should change that, it can't hurt. I will hook up a scanner as soon as I can pick mine up from my buddy.

But if the problem was in the o2 sensors wouldn't it cause the engine to run rich/lean and therefore be noticeable in the spark plugs?

p.s. no CEL

 

[silky]

one more question:

I don't know how to describe this...

anyways, on the upper intake manifold, below the plastic cover, there is a diaphram/actuator thing. It has a rod coming out of it and attaches to a hinge/swivel things which sits on a perch on the manifold. When I took my plastic cover off I noticed that the swivel part had popped off it's perch....the unit was not doing anything.

can you guys tell me what this thing is/does?

thanks