13MPG avg, and no codes??????
Thread Starter
Pro
Joined: May 2003
Posts: 671
Likes: 1
From: WATERFORD CT
13MPG avg, and no codes??????
Hello, this is all I am getting ,I tried to pull any codes but there were none?Could a cat be clogged enough to cause that big of a drop and still allow the car to run ?
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: 13MPG avg, and no codes?????? (montie98)
To see if the ECM is going/staying in closed loop use the diagnostic mode described on my site (link in sig. below). If it isn't, determine if the O2 sensor or the coolant temp sensor is faulty.
You can have exhaust back pressure tested; any more than a few lbs of pressure drop across the cat pressure indicates a bad cat.
You might also look at spark plug condition and check the air filter.
You can have exhaust back pressure tested; any more than a few lbs of pressure drop across the cat pressure indicates a bad cat.
You might also look at spark plug condition and check the air filter.
Safety Car
Joined: Sep 2003
Posts: 4,504
Likes: 0
From: Charleston SC
Re: 13MPG avg, and no codes?????? (montie98)
I'm getting about the same. funny thing is the guage is reading average 22. I'm a lazy bum so I havn't gotten arround to checking it yet but I think I may see really high fuel pressure. I wish they hadn't quit putting fuel pressure guages in them.
Team Owner
Joined: Sep 2001
Posts: 62,160
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From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
Re: 13MPG avg, and no codes?????? (rkessel)
An O2 sensor will not always throw a code when it dies.
When mileage turns south thats the first thing Id inspect.
When mileage turns south thats the first thing Id inspect.
Race Director
Joined: Aug 2000
Posts: 14,130
Likes: 7
Cruise-In II Veteran
Re: 13MPG avg, and no codes?????? (montie98)
Guys,
Are you POSITIVE thats the mgp youre really getting?Did you compare it to the gas bars left on the fuel gauge?The reason I ask,is once in a while,you should hit the RESET button on the dash for the MPG and go from there.
A few times Ive seen 10-12 mpg because I did alot of local driving,but then once I got on the highway,I hit the reset button and it began reading nearly 30 mpg.
Then average down to 25 mpg or so.
Give that a try.
:)
Are you POSITIVE thats the mgp youre really getting?Did you compare it to the gas bars left on the fuel gauge?The reason I ask,is once in a while,you should hit the RESET button on the dash for the MPG and go from there.
A few times Ive seen 10-12 mpg because I did alot of local driving,but then once I got on the highway,I hit the reset button and it began reading nearly 30 mpg.
Then average down to 25 mpg or so.
Give that a try.
:)
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Melting Slicks
Joined: Jul 1999
Posts: 2,875
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From: Olive Branch (Memphis suburb) MS
Cruise-In II Veteran
Re: 13MPG avg, and no codes?????? (montie98)
I would replace the O2 sensor(sensors, not sure if you have 1 or 2). They can get coated over time and not function well without setting a code, plus the early ones are cheap(less than $20). If you haven't changed the plugs in a while, go ahead and do a tuneup. :steering:
Drifting
Joined: Jul 2003
Posts: 1,613
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From: Orlando FL
Re: 13MPG avg, and no codes?????? (montie98)
I just changed the O2 sensor in my 85 cuz i was getting about 13mpg too. this tank, so far, i am back up around 15 (all town driving). I'll see how this goes and keep changing things out (plugs, wires, ait filter, maybe even gut my cats). Anyway, the O2 sensor was a breeze to change. Easy access (drivers side exhaust, just before the bend to go to the cat) I got a Bosch from Discount Auto, twisted it out and plugged the new one in. It even came with antiseize already on the treads :) $20. 1 year warranty. change it out and see what happens :thumbs: