Hey all, me again. But with a problem this time. I've read around on the forum and done some searching, and have my own ideas as to what I need to do.
Anyway, the problem is, I'm getting 7.8 mpg, and it has a pretty rough idle. It's the 5.9L 4x4 QC short-bed. Yeah, I know, not the best for mileage, but I should still be getting at least 10 I'd think... I don't drive it hard at all...I rarely get it above 2k rpm.

So, I plan to look at: O2 sensors, cat, and plenum gasket. Should I check the IAC too, and look at the ignition system too? I figure the poor mileage has to be tied in with the rough idle, so once that's gone, I think the mileage should go back to normal. What do you all think?


Thanks in advance for the input!


Oh, if I do a tune-up myself (plugs, dist, rotor+cap, wires, ect) does the computer need to be like re-calibrated? I heard this, but am wondering if there is any truth to that.

 

[align=left]O2 sensors, cat, and plenum gasket. - good start.
tune up - plugs, wires, cap, rotor - also good.
iac only controls idle speed. when this goes bad you experience fast, slow, or surging idle. nothing to do with mpg. ignore for now.

resetting the computer is a good idea after any maintenance. disconnect negative battery cable and turn ignition switch to 'start' position for 30 sec. this dumps the stored memory and causes the computer to reload default settings, which are actually good settings, but not the best mpg. it will "learn" from its sensor feedback and tweak the fuel settings. some people do this before racing to get the richest settings. it won't hurt anything.
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Hey thank you very much for the reply, that really helps a lot.