More milage problems

[97chevyman]

Boy this truck is starting to get really old, really fast. I have so far replaced the fuel pump and relay, due to low fuel pressure, also the inline fuel filter, now i have good pressure. I replaced the upstream o2 sensors because the computer said they were not registering anything, they are now with the new sensors. Replaced the MAP sensor due to the vacume reading and the actual vacume reading being off, now they are one of the same. Now my motor only has 40K miles on it. This is a 97 chevy 2500 2wd with a 350 and a 4l80E tranny. I never rev the motor over 2500 RPM, and it gets oil changes every 3K. I am getting 10.6 MPG, GM say 18, what am i missing here? I let it warm up about 5 minutes in the morning, never use the defroster or a/c. It is coming up to temp, but for some reason whenever i connect the computer up to it, it say open loop mode, even though it is up to temp. The computer i registering to correct temp. What am i missing here? Also ran 2 tanks of sea foam through it with no help.

[Faze2183]

our c2500 chevys get about the same milage

one thing u could do is a tune up like replace the spark plugs, wires (replace those 7mm stock wires with 8mm or some msd 8.5s), new cap and rotor uhhh i might be wrong but for work trucks that extra 2 miles per gal helped alot

[chevytrucks92]

Part of your problem is letting the engine set and idle for 5 minutes. This kills fuel mileage. With that said however, I do the same thing when its cold, lol. It hurts my mileage, but not really bad (maybe 1 or 2 mpg). Other then that, I agree with Faze2183 in suggesting a tune up. Changing the plugs, plug wires and distributor cap along with the air filter will probably help you out a little.

[MSpring]

If Your Computer Is In Open Loop Mode Then The Computer Isnt Using Any Of Your Sensors In Order To Give You The Optimum Gas Mileage. Check The Computer For Stored Codes.

[Ezee5]

Also you might read the fine print on the sidewall of your tires.. It will tell you what the actual air pressure is to have in them.

[toivo]

find out why you don't go into closed loop. probably the temp sensor.

[97chevyman]

temp reading 195 normal temp. I found something out though. The shop teacher told me that the fuel system should not hold pressure, and it should. I would have 50 psi with key on, it would jump up to 65 and drop to 50. I am getting a new regulator and replacing it, i check for leaks and there are none. Last time i trust that idiot. It wouldn't even hold pressure for 30 seconds. I think that is the problem. Air pressure is fine. I also checked my injector poppets and none are stuck, that good news atleast.

[Jeremy-WI]

They should hold pressure(60-66 psi) for a while. After I replaced my regulator it held pressure for at least 10 minutes(when I took the gauge off). Don't be too hard on the teach, I am fairly sure either the new body style or the pre-96 aren't supposed to stay pressurized, probably the pre-96 TBI

Sorry I lost track of the other thread, must have been either swamped with work or out fishing

[97chevyman]

i replaced the regulator and night and day difference in the ass-o-meter, we will see what she's gettin for gas milage here in about a week, i will post back.