can someone please help me please?

[transman81]

I have a 03 trailblazer ls with the 4.2 liter. It has around 145,000 miles on it. I just replaced the plugs, air and fuel filter, thermostat, fan clutch, cleaned the cpas, and disconnected the battery for 45 minutes.I also cleaned the throttle body. I am getting horrible fuel mileage. I can drive on the flat no hills, no stopping, at 65 mph for 70-80 miles and burn up 6 gallons of gas. My problem i noticed is that the calc load is at 100% all the time. As soon as i put it in gear and barely push the gas it hits 100%. Ideling it is around 30%. My upstream o2 is bouncing up and down so fast on the reading i cant hardly read it. I am leaving sunday for a 450 mile trip one way and if this is not fixed i will be sick when i get home of how much money i spent in gas. If any of you can help me please please let me know what you think....

[maxwedge]

I assume no codes, usually this would occur with very poor mileage. many things can cause poor mileage, there is no easy answer here, aggressive tires, bad o2 sensor, 4wd engaged, look at fuel trims and see what they are, post back. Engine load is calculated by the the tps and map sensor.

[transman81]

Originally Posted by maxwedge

I assume no codes, usually this would occur with very poor mileage. many things can cause poor mileage, there is no easy answer here, aggressive tires, bad o2 sensor, 4wd engaged, look at fuel trims and see what they are, post back. Engine load is calculated by the the tps and map sensor.

Ok i will look this evening and post back. It is a 2wd and i have new delta sierradial as tires on it. I will let you know what it is. Thanks for helping me.

[transman81]

Originally Posted by maxwedge

I assume no codes, usually this would occur with very poor mileage. many things can cause poor mileage, there is no easy answer here, aggressive tires, bad o2 sensor, 4wd engaged, look at fuel trims and see what they are, post back. Engine load is calculated by the the tps and map sensor.

When im at idle sitting still in park the short is pos 1 to neg 9 - 117-127 and the long term is neg 4%-123. after a short 5 minute drive when i get back and park the short sits at neg 20%-103 and starts falling after a minute or so and the long is neg5%-121.

fuel trim cell 20
aif flow is 5 g's
map 36 1.37 (kpa,v)
app ind. angle 0%
engine load 29%
ECT 201 F
IAT 147 F
air fuel ratio 14.6:1
spark 12-15
Ho2 sensor 1 70-905 mv moves very fast
sensor 2 117-799 slower than sensor 1
I have a master tech 2 scanner i can look at alot of stuff just dont understand all of it yet. I am not familer with the fuel trim none at all. The o2's either. If you need to know anything else i can look and see. Thanks again for helping me. Do you think i should change the upstream o2?
closed loop. when it idles a minute and i give it some gas it will just about die and then rev up.

[maxwedge]

Based on what you are reading the pcm is trying to lean out the engine based on high negative fuel trims, but why? Take a key on engine off baro reading and compare it to your area. You can change the readings from kilopascals to english also. That you way you can get better engine idle vacuum readings and baro pressure.

[transman81]

Originally Posted by maxwedge

Based on what you are reading the pcm is trying to lean out the engine based on high negative fuel trims, but why? Take a key on engine off baro reading and compare it to your area. You can change the readings from kilopascals to english also. That you way you can get better engine idle vacuum readings and baro pressure.

What do you mean to your area? Meaning outside or what? Kinda confused. I will see if i can figure out how to change it from kilopascals to english. Thanks a million.

[j cAT]

Originally Posted by transman81

What do you mean to your area? Meaning outside or what? Kinda confused. I will see if i can figure out how to change it from kilopascals to english. Thanks a million.

with no DTC codes and 10MPG this seems to be a fuel delivery issue or plugged cat/muffler/exhaust.....

if the O2 sensors or MAF/MAP had problems codes would be thrown.

if the injectors are leaking down the cat converter will get damaged and the MPG drops.

[maxwedge]

The local weather bureau can give you the barometric pressure, see if the scanner/map sensor agrees.

[j cAT]

AT IDLE the air flow should be higher than 5 ..........

could be restricted exhaust with this lower number it cant suck unless it can exhaust .

[Joe W]

I think that j cAT offers valid suggestion between fuel delivery, but more than likely a plugged cat, although I really appreciate maxwedge's suggestion regarding the local weather bureau display of the barometric pressure to use as a tool.

[Surg]

Had the same issue withe my brothers mitsubishi did full tune up coil packs injectors new cats etc probably $1500 worth of parts did nothing found out the timing was off reset timing was a serious job but no parts needed no it runs like a champ