Bad O2 Sensor? Cat? What is this telling me?

[BuffaloXplorer]

Generally, i let it run 15min. in the morning to warm up - i KNOW that is costing me mileage, but i've always done it and my mpg continues to drop like a rock. I got EIGHT MPG this last fillup (today). 151mi on NINETEEN gallons!!!!!! WTF!

With CarChip - it tells you if there's something causing an open loop and nothing thus far.

I looked on eBay at cats, but no $$$$ for that at the moment. Will soon, though.

 

[BuffaloXplorer]

I did manage to pull almost 13mpg this weekend - primarily short highway trips w/very few stop-n-go travels. Most of the highway mileage was while doing between 70 & 80mph.

 

[monkeydude3]

what a mouthful... I have a 1994 OHV with bad fuel milage, but that's because half the time I'm idling it diagnosing crap. Check your whole intake passage including the air filter and MAF and see how those are. I'd run some cleaner through the fuel in an attempt to clean the injectors, and try a little sea foam. Also, do you have 4X4? If so how much do you use it?? If that is left on I know running 4X4 all the time sucks gas like a biotch.

 

[monkeydude3]

I also have another possibility... I had a look at your cardomain site, and how often do you run all that stereo equipment? Usually if you have that on with the engine it puts a decent sized load on your alternator... that may suck some gas, let along the physical weight of the sub box... Just an idea

 

[BuffaloXplorer]

Thanks for your input...

I've done all the injector cleansing & seafoamed 2x over the past couple months. New KKM (had made no mileage difference wither way) and i clean the maf on a regular basis (every oilchange or so).

I agree that 4x4 sucks down the fuel, but i try to use it sparingly. I do believe that my most recent 8 mpg tankfulls were mostly driving with 4x4, but the 10-11mpg at all other times baffles me.

I had to make some repairs to the subs and drove w/o them for 2 weeks - no huge difference (poss. .5mpg due to the weight).

 

[Rhett]

The carchip graph output is really great...yet another reason for me to go OBD-II when my OBD-I 4.0 wears out.

 

[TPLYNCH]

Would a faulty fuel pressure regulator cause those 02 readings? I don't know how to read those printouts, but quite impressive... I do know if the FPR is dumping gas, it'll affect you milage.

 

[Rhett]

Would a faulty fuel pressure regulator cause those 02 readings? I don't know how to read those printouts, but quite impressive... I do know if the FPR is dumping gas, it'll affect you milage.

Reading this thread, and all that Buff has replaced and tested, I would have thought that a possibility too...but then Buffalo said he tested fuel pressure at the rail and it was ok. But that makes me wonder, what is the fuel pressure doing when he's driving around? On my OBD-I truck, I don't know of a way to test it while I'm driving, unless I went to the trouble of installing a fuel pressure gauge on the A-pillar or something like that.

 

[Kingkobra]

WOW...Some of ya'll are way out there...Thats why OBD Diags should be let to the trained people. If you had excessive fuel comsumption (high long term trims) you should set a code. Just as you should have set a code for the inactive cat converter. the downstream O2's are fluctuating too much. The highs and lows in the graph aren't intake and exhaust stroke, they are the computer switching the fuel mixture back and forth from lean to rich. Thats how it maintains a stoichiometric (sp) mixture.

I understand ya'll wanting to save money and all, but by the time he does all the tests and repairs you suggest, he could have had it diagnosed and repaired (also count fuel savings in this over this 4 or 5 month time frame), for less money and had a cleaner more effiecient runnung vehicle. As it ends up, he's still probably not fix'd, and it appears a re-flash is in general order. Which I am sure he will have to go have done unless he happens to have an NGS, a laptop, and the lastest flash software to do it...

Remember.....sometimes you have to break down and let a pro do what he does best.
You don't go to a plumber for legal advise nor do you go to a mechanic when a technician is needed.

No dis-respect intended....