Vilpo

But do you mean 4.2 or 3.6? On 4.2 i get usually about 12mpg and thats mostly city driving, but i've never gotten over 16mpg overall, even with mostly highway.

Calbha

from what i understand you should get better mileage with a 4.2 as they have more power to get up to speed. unless you floor it all the time which i can understand....:P

V8QinNJ

Okay then I'd look for "there's something wrong there" - that said quality fuel makes a HUGE difference - I only use 93 Octane.

Then if there is nothing "wrong" with the car I'd look for brakes dragging, carrying a dead guy in your trunk.. things like that. On my chipped 3.6 I *start* looking for things when I drop below 19MPG overall; and I check milage every tank. (math not the instrument cluster).

You could have dirty injectors, a not so good FPR.. a slow to act O2 sensor, Hall sender problem there is a lot that goes into it but the bottom line is - there is still something not right.

The 4.2 cars usually average 20+ MPG (overall). But I also don't race light to light either.

Vilpo

Ok, well i run 98 octance at the moment, fpr replaced, fuel pump replaced, hall sender checked, maf checked, tps checked. All these sensors checked from ecu end so that should count out the wiring also. So not many things that could be the reason for lower mpg..
Also i've noticed the consumption go up pretty much on the display, when i give a just a little more throttle.

Vilpo

Ok, i just noticed that my radiator fan spins all the time.. Even with engine just started cold. Could this keep engine too cold, and cause rich mixture?

Kneale Brownson

The electric fan or the viscous-drive one driven by the serpentine belt? The serp belt fan would turn whenever the engine runs. I THINK it slows down with higher engine speed because you'd then have air being pushed across the radiator by forward motion. The electric one should only run when the coolant is starting to heat above "normal".

V8QinNJ

And to add Knele said, if the electric one is spinning I'd look at a coolant sensor (or BOTH of them). if the coolant sensor is always reading too hot or too cold the ECU will dump in too much fuel (closed loop - runs rich) to get the car to heat up quicker.

Vilpo

It is the viscous-drive one. But i would think it's only supposed to run when the electric clutch engages it? Does anyone have the resistance specs for the sensors, the one for the fan and the one for the ecu?

Kneale Brownson

Again, you would need fan operation more when sitting still than when moving.

I don't recall there being any kind of electrical attachment to the fan assembly. I think it's a viscous drive.

Vilpo

Yeah, i guess you are right. So i guess it's normal for it to run all the time.. But i would think the engine isn't heating as quick as with an electric fan..?