Wyoming B.S. Thread

Were talking about the little red truck right?

Wheels/tires make the most difference in terms of MPG changes. Its not just size either. Unsprung weight seems to have a disproportional impact.

It's hard to see how an exhaust leak would have that kind of impact.

 

Wouldn't the exhaust leak before the the cat result in the 02 reading lean, tricking the truck into dumping more fuel? Combine that with bigger tires and winter gas and seems reasonable amount of drop.

 

Noticed it ever since I drove Igor home from Powell from surgery just before Thanksgiving.

So putting around, our trip down to Death valley(which I figured the fuckin shit head winds on the way south impacted obviously, but really wasn't any better going north or since) and I've been daily driving it for the last week +. So well into 20 tanks I say.

I don't have a way to check fuel trims, need to figure out the codes for the scan gauge. But that is something I'd like to look at for sure.

I could get on average 14-18mpg per tank Id say, I don't keep nots like you. But usually was 15-17 all around(up to 19-21 on the highway). Now im getting 10-13 all around and never more than 14 on the highway..

Igor not red truck.

Yeah i know all that. But for instance, right now Igor got new tires as you know which are larger but not a massive difference. Some i mean i was expecting 1-2mpg hit for sure. But this is a bit more extreme. And no im driving around with no weight in igor at all and still Im getting 10-12 on the way to work(more uphill, very gradual though), and 14 going home(down hill but again gradual).

I figured that if it's leaking before the rear O2 it would be dumping extra fuel.

exactly what I was thinking. But im also not sure.

 

I had a pretty significant exhaust leak all the way home from DV. It was between the header collector (so after the upstream sensor) and the cat. This did not produce a cel and I was getting some of the best MPGs i've seen in quite some time.

 

Gotcha. Over that period of time is plenty; just wanted to make sure you weren't doing the thing that a lot of folks do which is over a 50-mile period or a single tank or something.

I think you need to look at fuel trims. Lots of places have the codes for those. Mike does, I think. You could also have a vac leak in the engine bay - I'm assuming you've looked for that? I mean, you did have the engine out and all that crap unplugged. Would line up with the timeline at least. Spray a little starter fluid around in there.

Then, start keeping track of fuel consumption, even just for a few tanks, to make sure you're actually seeing the drop you think you are. Who knows, maybe it feels like a lot, but is actually just the 1-2mpg you'd expect from bigger tires.

Mike can confirm if these are the codes; just found this in a search of TW, and don't use a SG myself, so haven't tried them.

 

I am not saying you shouldn't check/monitor fuel trims but the downstream sensor only monitors cat efficiency. It does not provide any feedback to the ecu for engine performance. So anything that is happening after the upstream sensor is not effecting the fuel trims.

 

How are your compensating for the larger diameter tires "error" on your odometer?

Bet it sounded good too haha

 

Zane said is sounded like an old lawn mower when I passed him under full throttle. haha

 

I'm not sure his hearing has ever fully recovered from his exhaust situation in DVNP....

 

true, I have poked around in the engine bay a few times now assuming the same thing. But didn't see much. 03 doesn't have nearly as many vac lines as the earlier ones so much less stuff to fuck up. But will check again.

I'll try some of the codes and see what happens.

warms up next week too which should help to let me poke around more. Not really wanting to do much in the dark in -15.

Yeah thats what I wasn't sure about, couldn't remember. To me it sounds like the leak if there is one is right by the O2.

Not using my odometer for that. Plus these are just 33s as well. But going off my scan gauge numbers only basically for average mpg. It's pretty obvious though that im drinking fuel at a high rate though given how much more Im having to fill up. Tank used to last a week driving to work. Not its like 4 daysish.

 

These codes for short and long term trims for bank one appear to be the same as what I am using.

 

Your scan gauge is pulling the same data as the Odo so unless you've added a correction there, your scan gauge will be showing worse than actual mileage. Sounds like your data isn't real solid or reliable. Do the calcs manually when you full up and keep it in a spreadsheet.

 

Right but my point is that i've never had it calibrated. And im not seeing a 5% difference here, its 40% which slightly bigger tires are not going to do that big of a change. I mean we are talking like 1-2% taller and 4% wider. Its not like a slapped 35s on it. They are just a touch taller than my other 33s and are a bit wider.

 

The scangauge does have a way to correct for tire size changes and for gear ratio changes but Monte doesn't use it. It is used at each fill up and compares how much fuel was actually used compared to how much it predicted. It take a couple of tanks to fully adjust it's prediction numbers but I've found it can be quite accurate if the adjustment is made diligently at each fill up.

 

40% is what you feel it's doing but you don't have data to actually prove that out. That's my point.

Go do the easy fixes. Check air filter, clean maf, replace plugs and wires if they are due, lube the driveshaft and go check your exhaust leak. Actually track your economy at the pump the "hard" way and see where you end up.

 

No i use. Just didn't on the trip. Its back to within spec now under 6% when i do fill ups.

My data from the scan gauge I think is pretty accurate. If it ways im getting 10mpg avg, Id say its within 1-2mpg easily. And it used to ready 15-17 is my point.

Just about all those other things are new(plugs wire(30k on them) and coil packs(10k)), probably due for a new air filter. Doubt I could lube the driveshaft haha fuckin cold dude haha

This truck should not be drinking fuel at Frankenstein capacity given its like 1600lb lighter with much smaller tires. I know its not going to get great mileage, never did. But this is a bit extreme. I've been watching it long enough to know that something is off and more math and tracking of gas isn't need to know that.



But it doesn't sound like my first thought(exhaust leak) would be causing it. So keep looking and i'll buy some new exhaust gaskets either way.

 

Put the codes in. Trims don't seem wild. Seems to sit pretty close to 0 and occasionally gets to 3 on long term.

 

That seems fine for long term. What is the short terms doing?

 

bounces around a bit but not a ton. on the highway it stayed on 0 mostly. -4 to 3ish id say during other stuff


I did notice today that my EVAP canister under the truck makes noise after driving and parking it. Never did that before. Makes the same groans my earlier trucks make.

 

Trims seem normal. Look elsewhere.