Travieso
Boooooooost !
i get around 14-16 on my tahoe.. everything stock except exhaust.
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Hello. I am having a similar problem with my 2002 Yukon XL. When I bought it a couple of years ago, I got about 18 (US gallons here) mpg on the way home. Gradually it became worse and about a few weeks ago it started stumbling and running rough cold and warm. Replaced the fuel pressure regulator and both front o2's.
Put on the easy xray 6000 and it showed about 2-8 misfires on one single cylinder (6). Before I replaced the goodies it would have multiple misfires (P0300), some up to about 300/500. No everything is running the way it should, smooth and no codes.
Starts much easier too in the morning.
But now the mpg got way worse than before.
Before the trouble started with the o2's and the regulator (and still running normal), I got about 13-15, no matter how long or short the trip was, but on regular gas it would be around 15, on E85 (flex engine) it would run about 13 mpg.
It was much better in the beginning, like 15-17-18.
Fuel filter got replaced about 1-1.5 years ago. I don't really think that would be the problem, but I can't find anything else that could be wrong.
I could put up some pictures of what the easy xray 6000 said when I scanned it.
One thing is way off, the a/f ratio. It is on a steady 10.3, which I know is totally off (doesn't matter if I have the pedal down or at idle). No mods done to this truck.
Alcohol content sensor... That was a new one. Never heard of it before. It doesn't have a muffler anymore. Cats still original I guess. It has no problem revving up to 4-5k and for a 2,600 kg car, it really keeps up with the rest of the traffic, no problems there.
I still have to find a place where they flow test injectors. Not too many places around here in Sweden where they do that.
I did find a wire to the cylinder 1 coil to be in a bad shape (bad repair from a previous owner?). Haven't taken a closer look to get the thing out so I can fix it properly yet, but that might be one reason to why it all of a sudden can start a misfire.
The behaviour changed now to a scenario where the whole left bank starts to misfire under load (going up hill with a trailer).