O2 sensor replaced and even worse gas mileage

[rizzjc]

So, I've been getting a P0153 on and off for .... a long time. I finally replaced the primary bank 2 sensor, and my had mileage dropped even lower than it was before. Back in the day I was getting 16.5 pretty consistently. Then before my head gasket blew I started getting 12-13. That didn't change when I got a new engine put in. Now with the new O2 sensor, I'm not even sure I'm getting 10! I haven't calculated it yet, but I know it's gone down a lot.

Any thoughts? I'm thinking cats, but why would replacing the O2 sensor make it worse? No new codes since I replaced it. I reset the computer as well.

 

[Abbondanza]

Are we talking highway or more stop and go city? I rebuilt my v6 top end (including replacing my bank1 upstream o2 sensor) and I get 12 city, 17 highway. Did you remove the negative battery terminal for 10 minutes to allow the computer to reset and learn the new o2 sensor flow? (I read to do this when I replaced mine).

 

[jremington59]

I have an O2 code that comes and goes and it doesn't affect the gas mileage. I'd look at plugs, wires, fluids, air filter and be sure to clean the mass air flow sensor. You also might want to make sure there are no calipers grabbing. I got a 2000 a while back and over the first three tanks combined I was averaging 17.8. I pulled the MAF and you could see the filth on it. I gave it a good cleaning and over the next two tanks it's gone up to 19.5. I drive the same routes all the time, which is mostly highway with a few small towns/cities. I will admit my 97 5.0 would never get that mileage and I'd say 17.5 is about the best I get with that one.

 

[rizzjc]

Sorry for the late response. Other catastrophes going on. This is "mixed" driving, but pretty much highway. I thought about the maf, and need to pull it and clean it up. Probably need to do the o2 sensor on the other side. It's thrown the code, but not recently, or as regularly. I'll look at all those things before a replace cats. I can't remember now if the plugs were done when the engine was replaced. You'd think so, but then who knows what they put in there. Wires aren't that old.

 

[Bigham]

how do you know if the 02 sensor is bad? WHat happens if you dont replace it?

 

[Tbars4]

..A couple things to look into...

..First, verify the code since P0503 represents VSS...

..If it was truly the o2 sensor, adding a good sensor may now have changed your fuel settings with the computer using the last info it had if you did not reset (disconnect battery) but it would switch values between 50 miles and a full tank...

..and it does sound like you are do for a basic tune up..

 

[rizzjc]

Well, I did reset the computer. Pulled the battery cable. Then let the truck idle for 10 minutes.

I shouldn't really need a tune-up on a brand new engine, but as it turns out, I kinda got screwed by the engine shop, so I guess nothing should surprise me.

And to answer the question as to how you know the o2 sensor is bad, the computer will throw a code and tell you.

 

[Turdle]

I am highly suspect of the cats also Joe.

However, a set of spark plugs might make a difference. Have you tried cleaning the maf sensor? Are you absolutely sure the rear drum e brakes are not dragging a tad? Do the diffs and transfer case seem to be holding fluid well?

I'm not 100% sure about this, but the new sensor on one bank might have affected the fuel trims. Did you replace it with a ford sensor?

 

[koda2000]

Well, I did reset the computer. Pulled the battery cable. Then let the truck idle for 10 minutes.

I shouldn't really need a tune-up on a brand new engine, but as it turns out, I kinda got screwed by the engine shop, so I guess nothing should surprise me.

And to answer the question as to how you know the o2 sensor is bad, the computer will throw a code and tell you.

not necessarily true.

 

[rizzjc]

I am highly suspect of the cats also Joe.

However, a set of spark plugs might make a difference. Have you tried cleaning the maf sensor? Are you absolutely sure the rear drum e brakes are not dragging a tad? Do the diffs and transfer case seem to be holding fluid well?

I'm not 100% sure about this, but the new sensor on one bank might have affected the fuel trims. Did you replace it with a ford sensor?

No, Denso sensors, I think. I got two, but only got the one done so far. It gets better though. You're gonna love this ....

My fuel mileage had NOT dropped any more. It still sucks, and I need to figure out out, but it didn't changed after replacing the O2 sensor. Are you ready for this? My stinking odometer died. I didn't notice until I was going somewhere clocking the miles. So, 208,912 miles forever.

 

[Tbars4]

..Then the code for the VSS may have been the correct code?

.If so, here is the only info I know on it..
http://www.explorerforum.com/forums/showthread.php?t=243947&highlight=P0503

 

[rizzjc]

What's VSS?

 

[Tbars4]

..It is the Vehicle Speed Sensor aka virtual speed sensor..

http://www.explorerforum.com/forums/showpost.php?p=2085739&postcount=7

 

[rizzjc]

Well, that is in the transfer case. Is there another one. I wouldn't have been near that.

 

[rizzjc]

And I didn't have a VSS code, I had a primary O2 bank 2 code.

 

[rizzjc]

Oops! I'm dyslexic or something. It was P0153, not 503. Sorry about the confusion.

Fixed in the first post.

 

[Tbars4]

..Just going off the code in the first post and it would reflect an erratic VSS before failure..

..96-97 had them on the t/c with a plastic gear like the first gens..You might just have a bad plastic worm gear in the instrument cluster..

 

[jremington59]

No, Denso sensors, I think. I got two, but only got the one done so far. It gets better though. You're gonna love this ....

My fuel mileage had NOT dropped any more. It still sucks, and I need to figure out out, but it didn't changed after replacing the O2 sensor. Are you ready for this? My stinking odometer died. I didn't notice until I was going somewhere clocking the miles. So, 208,912 miles forever.

Alright, you jinxed me, lol. I took my 97 for a ride tonight and the damn odometer, trip meter stopped working.

 

[Turdle]

You could either replace the worm gear-( hassle)

or get a different cluster, They are all over ebay with various odometer readings

or, get a scan gaugeII.

The scangauge will keep track of your fuel economy and miles traveled, also give real time MPG, and several other functions--gauges-code reading and clearing etc

http://www.amazon.com/ScanGauge-Aut...F8&qid=1373514915&sr=8-1&keywords=scangauge+2

 

[rizzjc]

Well, the odometer started working again this morning. Best I can guess is that it didn't work for about 50 or 60 miles.

I do have a scan gauge. It still puts me at 13 mpg. I'm still going to do the other O2 sensor, clean the MAF, and then start looking at cats.