Today I went to fill up the tank and found that i went from the normal 12-14 MPG to 6.4. I was shocked, to say the least. What could cause such a thing? As far as maintenance, the spark plugs were changed this previous summer, and regular oil changes. Recently, I have had an issue with an odd "missing" issue that would come and go. I believe it is/was the fuel filter, but i havent had the chance to fix it yet, as it hasnt been above freezing in a while. Could a bad fuel filter cause my mileage to suddenly drop as well? Any help would be great. Thanks guys.

 

Bad O2's or big vacuum leak. Hook it up to a scan tool and see what they are doing or the Integrators are reading. First tool any EFI powered vehicle owner should have

 

When i take it to autozone or where ever, what should I ask they look for?

 

Hard to give advise when we know nothing about the vehicle. Can't even tell you if AZ can scan it since we don't know what year it is.

 

Why not add a useful signature, with basic info about the car.... year, model, engine, trans and any major mods.

Did you consider the possibilty someone siphoned a few gallons out of your tank?

 

Sorry guys. I have a LE1 H/C 1995 z28. built 4l60e, 3600 stall. It has ~125000 miles on it.

 

They may only have a code puller, not sure, never went there to ask, I've always had a laptop scan tool. But you'll want to see what the left and right Long Term Integrators or BLMs (Block Learn Multipliers) are. A 128 is perfect, if your mpg is bad, then its adding excessive fuel thinking its lean, so a reading higher than 128 indicates lean...the higher off of 128 the more lean it thinks it is, I'd say anything over 140 is bad...
What could cause a BLM higher than 140... A lazy O2, a vacuum leak, or an exhaust leak before the O2..thats the most likely causes anyway.

Not sure fi you'll be able to see O2 cross-counts, but they should be cycleing from 0-255 in less than 90 secs for a healthy O2..some scanners do not show that, but if not, just look at the O2 values while in Closed loop and see that they are switching fairly rapidly and not stuck on the same reading for more than a few seconds....

If you don't understand the terminology I'm speaking above, then spend some time in the Computer/Diag forum and learn what these terms are It will help you in the long run.

 

How much money do scan tools usually cost?

 

You can get a self contained device like a Scan Master http://www.fullthrottlespeed.com (then click on link for scanmasters) for about $240

Or if you already have a laptop, there's several available for free if you have a cable, or some nicer ones for about $100.
http://www.ttspowersystems.com/
Buy cables and sw from http://www.akmcables.com/dss.htm

 

I don't think Autozone is able to pull codes on OBDI vehicles. If you have other vehicles, besides the 95, and they may be OBDII, you might consider a scan tool that can do OBDI and OBDII. Check Autoxray's site for some models. Hint: if you decide on an Autoxray unit, get a J. C. Whitney catalog and use the 15% off coupon.

 

Hey man thanks for this info; I've already checked out this site and found the information very helpful.

 

Im not sure about Az but I work at oreilly's and we can read anything obd1 and up. but only pull codes not read live data. so I'd assume thats all the zone can do as well.

post up on mofbody, somebody anound us has a cable. unless you can wait a couple weeks cuz i'll probably be getting a cable and I can try it out on your car if you want since my car is still down.

 

the scanner that comes in the soft case, its a can/obd scanner, i forget the maker. anyway it reads live data.

i work at oreillys to

you should have it in stock in the cage, the price is like 229.99 if that helps

after our discount its like 130.00

 

yeah I know which one your talking about. but i think he just wants a free scan. and since im obd1 i can get tunercats for free!