I hope this isn't a dumb question..
After my Nelson mail order 91 economy tune, my Scangauge is telling my I have 14.6 AFR all the time. I swear that before the tune it would vary as I drove, but now it stays constant at 14.6. Is this normal and built into the tune?
Also, at WOT it changes to 12.6, or 12.5 maybe. I sent Erica an email about it but haven't heard back, that's what makes me think it's supposed to be that way.

I am asking because I'm chasing my tail looking for 3-4 lost MPG's... this truck used to get 18-20 MPG on highway, between 14-16 in town, depending on the week. Now I get 11-12 in town, 15-17 on the highway. I have a new fuel pump & filter, brand new Denso front o2 sensors, 10k on my plugs, e-fans, Nelson 91 economy tune, K&N FIPK, cleaned my throttle body, cleaned MAF with MAF cleaner, replaced PCV, checked EGR, properly inflated tires, Scangauge is not reading any codes...... I even have a hard bed cover and I'm really trying to get my MPG back, so don't tell me that I just have my foot in it. It's really bugging me. At this point, I just want to know if the AFR is reading correctly so I can rule that out.

Also, I'm planning some mods very soon and I want to make sure I'm running tip-top before I start changing things.

I'm running AC Delco plugs p/n 41-110 Iridium gap .040
Thanks.

EDIT - And I've seafoamed in the tank, seafoam in the oil, seafoam in the TB, water treatment in the PCV vacuum hose... trucks runs smooth and strong.

 

Are you scanning the AFR commanded pid, or the AFR actual pid? Sounds to me like "commanded".

 

Thanks for the response. I have to assume that you are correct about the commanded vs. actual sensor reading because I do not know enough about it to answer and I haven't found the information from Linear Logic yet. I also have to assume that Nelson knows what they are doing since the truck runs excellent with this tune. This was supposed to be an "economy" tune with everything I've read saying that MPG would increase. But I have seen a decrease and now I also pay more for 91 gas.

I guess the only thing I can do now is start putting back on the stock parts to see if I can regain some mileage.

 

if it was running good before the retune, and now worse MPG after the retune.. that leads me to believe the tune is off.
you can get a wideband to actually see what it shows.
what your seeing on your Scangauge is what the PCM is commanding.

 

I'm not going to put any blame toward Nelson, they know wayyyy more than I will ever come close too and I trust that they made the appropriate changes in the tune. The truck runs so good right now, hard to believe it has 50,000 miles, let alone the 150,000 miles that it actually has on it.

My mpg's went down about a year ago when I added the K&N FIPK, I've had another thread about that. My Dad experienced the same thing when he originally put the K&N on around 50,000 miles, saw a decrease in MPG so he took it off. I was hoping to drive the truck for a while to see if I could get the MPG to come back up, but it hasn't.

I think the best thing to do would be to data log a wideband O2, like you said, and send the info to Nelson so they can tweek my tune. I've done some looking at gauges, not sure which one is best for my needs. Nelson sells the PLX DM-6 with a wideband. Hard for me to spend $200 on a single gauge that I won't use after the datalog.

 

If you ever do any more serious mods like FI or nitrous you will want to have a wideband hooked up at all times.

 

I would say get the gauge and leave it installed. You never know just when you may need it, and it's always nice to be able to know you can keep an eye on things while you're out running around. Also, see what happens if you swap out the K&N filter for something that's not oiled. I know you cleaned the MAF, but I've just heard to many people having trouble with the filter oil causing issues I don't really trust those filters as much anymore.

Also my economy usually takes a bit of a dip right after a tune, just because my driving gets a little more "spirited" without my even thinking about it. Just some food for thought haha.

 

Just to be clear for anyone who may read this in the future, Nelson performance has done an excellent job with this mail order tune that I recieved. It is amazing the difference from stock. I am only trying to troubleshoot my MPG loss and giving information about my truck. If I had to choose, I would take the Nelson tune over 3-4 MPG loss anytime. Obviously I don't want to choose, so I'm looking into it. I'll be swapping the intake back to stock to see if that helps. Erica has been more than helpful answering my emails to help me troubleshoot, which I understand they don't have to or need to, but are willing to try and help me out by providing a little information.

Thanks for all the responses.

 

Well, ill ask the obvious, was your tune running lean before the tune?

 

The "spirited driving" is definitely something to consider and I was seeing some of that after the tune, just because there was such a dramatic change from stock. That's why I've waited 2-1/2 months to start worrying about it and I've consciously tried to drive less spirited... easier said than done!

And I can't answer if the previous tune was lean or not, I have no way of knowing.