TBI Running Rich 13 MPG

[lycan]

My TBI 350 has a roller cam, 305 heads, -5 CC dome pistons, and I'm running a 350 computer.

It seems to run rich, smells like it and I'm getting 13 MPG, which is definetly not right.

Any idea what could be causing bad gas mileage?

I replaced the oxygen sensor when I finished building the engine. I can disconnect it and the truck runs the same...

[rudedogg]

try replacing the coolant sensor that sits on the intake near the thermo housing,possibly the o2 sensor is bad or your map sensor is bad. have you checked for codes?

[lycan]

It has not given me any codes. I replaced the thermostat and oxygen sensor when I rebuilt the engine, but the map sensor is still old.



btw, it's funny that I'm a freshman and you're listed as a senior even though I registered before you http://www.s10v8.com/images/smilies/icon_razz.gif

[rudedogg]

try replacing the coolant sensor that sits on the intake near the thermo housing





yeah it is ironic huh!

stay on the board,i was off for about 8 months total. http://www.s10v8.com/images/smilies/icon_frown.gif

[riotpolice75]

run down to autozone and rent a handheld vacuum pump and get an ohm meter if you dont have one. draw 10" of vacuum on the map sensor and take the voltage reading.

3.5 to 5.1 V at 2000 to 3000 ft

3.3 to 5.0 V at 3000 to 4000 ft

3.2 to 4.8 V at 4000 to 5000 ft

3.0 to 4.6 V at 5000 to 6000 ft

2.9 to 4.5 V at 6000 to 7000 ft

2.8 to 4.3 V at 7000 to 8000 ft

2.6 to 4.2 V at 8000 to 9000 ft

2.5 to 4.0 V at 9000 to 10000 ft



if the voltage is different than that at your altitude then replace the map sensor.



85 ohms at 210 deg F

450 ohms at 160 deg F

1800 ohms at 100 deg F

3400 ohms at 70 deg F

7500 ohms at 40 deg F

13500 ohms at 20 deg F

25000 ohms at 0 deg F

100700 ohms at -40 deg F



thats the resistance values for the temp sender.



those are the two easiest things to check.



what fuel pump is in it? how much pressure? and what injectors are on it?







smith

[lycan]

wow great post, I'll do all of that tomorrow

as for the fuel pump, it's the one that came in the truck, a 2.2L pump....