What Could It Be

heavyduty guy · November 19, 2007

i changed plugs wires fuel filter ran techron in fuel cleaned throtlebody and 2002 6.0 still has a miss in it when going up hills,no code has showed up truck runs fine in all other cases,i am thinking this is why i am getting 9.5mph? anybody have any ideas? thanks

Rocco715 · November 19, 2007

Oxygen sensors might be the cause of your 9.5mpg. When you changed your plugs and wires did you make sure all of the coils were still good too? coil packs go bad. Could also try giving sea foam a try too.

heavyduty guy · November 19, 2007

how can you tell if a oxygen sensor is bad?how do you check the coils to see if there weak?

ujtruck · November 20, 2007

how can you tell if a oxygen sensor is bad?how do you check the coils to see if there weak?

you'll need a digital multimeter, then you have to find the wire connected to ECU (normally white) and the ground - start the truck, check the voltage it should go up and down,

The ECU expects the signal from the sensor to be oscillating from below 0.4v to above 0.6v, but not above 1.2v, every few seconds when cruising.

I have a O2 sensor simulator, so I can play with fuel trim. please follow the below link if you like to build your own simulator.

http://www.mkiv.com/techarticles/oxygen_sensor_simulator/

ooo 2 more cents:

if your reading is less than 0.5 your truck is running rich, if its over 0.8 then its running lean. I hope you'll understand my jargon

edit: if you see higher voltage from the O2 sensor, it dosen't mean it is bad - at this point check your cat.converter. If the cat.converter is clloged then more heat will build up there and increase the O2 sensor voltage. You may have 2 O2 sensors - check both of them.

heavyduty guy · November 21, 2007

how can you tell if a oxygen sensor is bad?how do you check the coils to see if there weak?

you'll need a digital multimeter, then you have to find the wire connected to ECU (normally white) and the ground - start the truck, check the voltage it should go up and down,

The ECU expects the signal from the sensor to be oscillating from below 0.4v to above 0.6v, but not above 1.2v, every few seconds when cruising.

I have a O2 sensor simulator, so I can play with fuel trim. please follow the below link if you like to build your own simulator.

http://www.mkiv.com/techarticles/oxygen_sensor_simulator/

ooo 2 more cents:

if your reading is less than 0.5 your truck is running rich, if its over 0.8 then its running lean. I hope you'll understand my jargon

edit: if you see higher voltage from the O2 sensor, it dosen't mean it is bad - at this point check your cat.converter. If the cat.converter is clloged then more heat will build up there and increase the O2 sensor voltage. You may have 2 O2 sensors - check both of them.

thanks alot i will test them saturday when iam home to see whats up with it i been trying to find out how to test them for a while,thanks agian

threearmsinjune · November 24, 2007

what kind of miles are on the truck? I had a truck do this when the cat converter started clogging up. Basicly what happens is that the engine has trouble exhaling and this could also be part of the fuel consumption issue. Whe you go up a hill you are asking it to work harder, but it cant breathe well and is missing. Food for thought. A good manual is going to go in depth a bit better.

Chris

heavyduty guy · November 24, 2007

what kind of miles are on the truck? I had a truck do this when the cat converter started clogging up. Basicly what happens is that the engine has trouble exhaling and this could also be part of the fuel consumption issue. Whe you go up a hill you are asking it to work harder, but it cant breathe well and is missing. Food for thought. A good manual is going to go in depth a bit better.
Chris

thanks,it seems to have a a certain spot when going up hills,when you gas on it hard it runs great,truck has 51000 miles on it