sinful

I have posted this several times before and have not found a solution yet. the symptoms are horrible mpg during city driving and normal during highway driving.

highway speeds the mpg seems to be normal. it can travel probably 100 km for every 10dls of gas. but during city or cruising speeds..............im spending 3 time as much.

im estimating low 10s mpg city and about 25 mpg highway.

Does the o2 sensor plays a big mpg factor during cruising speeds here?

sinful

someone mentioned the tps. im going to double check it again. my idle is a bit high and im having some trouble setting up idle. it either goes too low to where engines shakes or too high to where im probably wasting gas with a high idle.

abecedarian

The O2 can affect mileage in strange ways, particularly if it's bad.

Most people think the O2, when it fails causes bad mileage, which is normally true but the sensor can fail in several different ways. The most common failure mode for the O2 results in the ECU going rich. In more rare situations, the O2 can fail and send "rich" to the ECU, which causes the ECU to go "lean". Symptoms of that would be something like the engine tends to "ping" more than normal under light throttle acceleration or cruise, and possibly a little "less" power than you're used to when under light acceleration.

I don't know when last your O2 sensor was replaced, but typically they require replacement at around 80,000 miles, give or take.

A failing coolant temperature sensor or even a stuck thermostat could cause an issue like you describe though, too.

Crazy Hakachukai

Is it over heating at all in the city conditions?

Last time I checked 60% of all energy loss in a standard gasoline engine happens because of heat loss in the engine.

The hotter it gets, the more energy you will loose.

Just an idea... it could obviously be many things.

sinful

yeah there are a lot of factors here.

upon further diggin I discovered the truck has a stuck fan clutch and the 180 thermostat keeps the truck way to cool, about a quarter of the temp needle all the time. It takes longer for it to warm up and drop the rpms to normal in the morning or cold starts. And the radiator has 4 small pin hole leaks and the heater core also leaks.


I probably need to take care of the coolant system first.

sixstringslut

If you are not getting a CEL the O2 is fine.
180 deg thermostat should put you above mid-mark on gauge. I run 165s in mine and they run 1/4 to 3/8 in winter and mid-way in summer. If your 180 only gets you 1/4 the way on the gauge you have a stuck t-stat.

In theory hotter running engine will give you more power and mpg according to all the physics classes I had to take. Captains Law if I remember correctly, look it up. This is where the cold-air intakes come in (probably will not help mpg's that much though). Same reason they put radiator curtains on semis and tractors in the winter, it's not just for cab heat but to keep engine hotter for more power. Big problem with diesels but theory applies to gas engines as well.

The 60% that was mentioned before was energy loss to producing heat. A common by-product of I/C engines and is unavoidable as long as we need radiators. ( Still waiting for that cold fusion/fission motor to come out.)

There are too many variables in city driving to say you even have a problem.
My 88 2WD 22R can get anywhere from 15 - 35 mpg just by how I drive it and has been that way since it was new.
If you are getting 25mpg on the highway you are probably in the ball-park as the rest of us.

sinful

correct no CEL.

Indeed the motor has a 180 thermostat in it but the radiator fan clutch is not slipping during cold or hot and is draggin the fan blades to the max. when reving the motor the fan is always loud during cold or hot and the temp always stays 1/4 to 3/8 aprox. in the morning the truck takes longer to warm up and i think is due to the fan clutch issue.


it would be interesting to see an increase in mpg with a new fan clutch and with temps between 3/8s to 1/2 at the temp gauge.