'02 S10 Sudden Drop In MPG

[kmack]

I have an '02 S10 Extended Cab... 2.2L... 4cyl... 46,000 miles

Anyway, I had to take it into the shop about a month & a half ago b/c my Check Engine light was on. The shop charges $80 for diagnostics. Anyway, they hooked it up and told me that the problem was a faulty air pump. It was going to cost me about $400 to have it and the solenoid replaced. Long story short I ended up getting it goodwilled (I give them a good survey when GM sends them out, trust me it pays off sometimes).

Anyhow, about three weeks ago, I filled my tank up w/ gas. I also reset my trip odometer (I normally get about 350 miles on a full tank, about 20mpg). About 2-3 days later, my Service Engine light comes on, again. Anyway, I didn't really notice my fuel guage drop fast... but I hit E at about 260 miles.

Is there something that could be going on that could cause that big of a decrease in fuel efficiency?? It was almost 100 miles less than what I normally get on a full tank. I filled up again on Monday, and I'll double check just to make sure I'm not hallucinating.

I plan on taking it in soon, I just don't feel like paying the $80 just to have it hooked up for diagnostic right this second. However, if it's something serious, then I'll get it in ASAP.

EDIT: No noticeable fuel leak!!

[RahX]

what kinda temps? i noticed in mine (same year 2.2/5sp) that when it got cold my mileage plummeted and i was lucky to get anywhere near 300miles on a tank.

[dmbrisket 51]

as rhax stated, cold weather kills gas mileage, also at 46k its due for a new air filter and fuel filter, both can cause poor fuel mileage if clogged, other then that if you dont smell rich exhaust, have a code, or raw gas, i would blame it on the cold weather, however if the mil comes on, then we have a problem

[RahX]

if his is an e85 truck like mine was its probably got a pressure regulator in the fuel filter. the book says 90k is the service interval for that. also 90$ for a fuel filter is ridiculous.

[brandon200317]

when it was working, you only getting 20 mpg with the 4-banger?.. wow glad i opted for the 4.3 v-6, mines a 96 getting 21 mpg city, 23 hwy mpg.

[RahX]

well when its warm out i get about 400miles+ to a tank. Cold weather=teh sucks for mpg for some reason.

[brandon200317]

Originally Posted by RahX

well when its warm out i get about 400miles+ to a tank. Cold weather=teh sucks for mpg for some reason.

well ya, but i still got decent milage, i live in MN. (besides the fact i'd let it idle for 10 minutes each morning to warm up which dropped it down to 18 mpg)