Intake, Headers and Exhaust Custom Exhaust? New Headers? Need Opinions on Intakes? Discuss making your ride breathe better here.
Sponsored by:
Sponsored by:

Worse mpg after replacing o2 sensor!

  #1  
Old 05-26-2013, 12:10 AM
Junior Member
Thread Starter
Join Date: Mar 2013
Posts: 15
Exclamation Worse mpg after replacing o2 sensor!

I'm driving a 2002 Galant DE. Had vacuum leak, cat efficiency, up 02 codes. Replaced throttle body gasket and intake hose/tube. (Fixed leak/ rough idle)

And replaced the ORIGINAL o2 sensor (118k miles... :/) with the same exact Denso o2 sensor, brand new. Was getting 25 mpg mixed before, looks to be about 15 or so now.

I have NOT done anything about the cat eff. sensor code. WITH that being said, any reasons why my MPG could have gotten WORSE after replacing the o2 sensor??
 
  #2  
Old 05-26-2013, 02:48 AM
Banned
Join Date: Feb 2006
Location: Austin, TX
Posts: 16,176
Default

Did you replace the o2 sensor before or after the cat? Did you reset the ECU afterwards?

Perhaps the cat is a wee bit clogged. You can remove it and soak it in acetone/gasoline. That'll clear it up some. Just DO NOT put it back on till everything has completely evaporated off.
 

Last edited by Sebba; 05-26-2013 at 02:53 AM.
  #3  
Old 05-26-2013, 02:32 PM
Junior Member
Thread Starter
Join Date: Mar 2013
Posts: 15
Default

It was the upstream one before the cat, on the exhaust manifold. Changed o2 sensor in Advanced Auto parking lot, they reset ECU for me.

I haven't tried cleaning the cat, but it IS giving me a cat-code, so I'll try your suggestion and let you know.
 
  #4  
Old 05-26-2013, 08:16 PM
Banned
Join Date: Feb 2006
Location: Austin, TX
Posts: 16,176
Default

Reset the ECU yourself, remove the negative terminal on the battery with the keys in the ignition. That'll drain any excess power.

Make sure you remove the rear o2 sensor before you dunk it, that'll destroy the sensor. I would suggest replacing your air filter too.
 
  #5  
Old 05-28-2013, 06:51 PM
Junior Member
Thread Starter
Join Date: Mar 2013
Posts: 15
Question Looking for Knowledge!

Now I'm not an expert, so I'm not like insulting you or anything, but how would the cat have anything to do with the MPG? Isn't that (*and down 02 sensor) just purifying the exhaust that's coming out of the tailpipe, (*and measuring the contents of the refuse).

A friend of mine said something about it clogging, but I don't fully trust him. (Right after saying that, he asked how to fix his window because it doesn't go up)
 
  #6  
Old 05-28-2013, 06:55 PM
Banned
Join Date: Feb 2006
Location: Austin, TX
Posts: 16,176
Default

Because of the exhaust restriction, that's why it lowers fuel economy.

The o2 sensors directly effect fuel economy too.
 
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
fungusboy
Mitsubishi Outlander
7
12-13-2012 09:34 PM
Eclipse440
2nd Generation
10
01-16-2008 07:49 PM
burnmyeyes
Sights N Sounds
5
10-14-2006 02:38 AM
imtalkintou
Off Topic
324
04-15-2006 01:28 AM
94 3000gt
Mitsubishi 3000GT
5
09-20-2004 07:33 PM


Thread Tools
Search this Thread
Quick Reply: Worse mpg after replacing o2 sensor!


Advertising
Featured Sponsors
Vendor Directory

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.