Hi everyone, first post and hoping to get some information with more knowledgeable who know our vehicles. I have a 07 Yukon with the LMG 5.3 that recently had the cats stolen after I had a blowout and had to let it stay on the highway overnight. I got a local shop to just weld in some metal tubing and had a 93 octane tune put on it after it kept throwing codes from the missing cats. Now the issue is it burns gas quicker than I can put it in. Before the cats were stolen it was a quarter tank would take two days to burn and now it would just take a nice 20-30 min drive to burn it. It use to beat out my **** Pack in terms of MPG. Now it can't beat a C10 with a clapped out 350. What would you guys recommend I can do to get the fuel economy back to an acceptable level? Any advice, guidance, or info will be greatly appreciated.
Performance/Economy Issues
- Thread starter BoKo
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- 2007 yukon 5.3l
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NIevo
Full Access Member
Ummmm.....we need a lot more info. Obviously the tune isn't very good if you are running that rich.
Sorry for including everything, what else do I need to include to help give any advice?
NIevo
Full Access Member
What did you do with the O2 sensors that were in the cats, what mods do you have if any, who did the tune, why a 93oct tune if not modded.....etc.
O2 sensors were tuned out due to the thieves cutting off the portion that had them, no mods, and my father had the 93oct tune thrown on while I was out of town on assignment. It's pretty much a stock Yukon.
NIevo
Full Access Member
Something is obviously off on the tune. Need to find out if it was a generic "canned" tune or a custom tune. Sounds like your A/F ratio's are pretty out of whack. Plus, is there a reason for a 93 tune with no other mods? No reason to have to use 93 otherwise.
Understood and from my understanding it was a custom tune done a performance shop in town and you got me there. I just wanted to have the codes gone and this is what had when I got back. I'll go to the shop myself to see if they can fix and what they messed up.
NIevo
Full Access Member
Yep, I would definitely start with the shop because it sounds like a tuning issue if everything was fine up till that point.
Thank you, I appreciate it!
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Welcome to the Forum from NH.
Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.
I hope that you will become a participating member in the Forum's discussions.
Pics of the truck, please.
You are already receiving sage advice from the knowledgeable folks on this Forum.
Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.
I hope that you will become a participating member in the Forum's discussions.
Pics of the truck, please.
You are already receiving sage advice from the knowledgeable folks on this Forum.
donjetman
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Bad custom tune
NIevo
Full Access Member
Any updates?
Scheduled to take it in Wednesday for tune corrections.
Turns out it wasn't tune related. The main power wire and o2 sensor wire were cut when the guys stole my cats which I was told it was reading lean and dumping fuel due to those cut wires. It is doing better on fuel I will say but now I can tell it needs a fresh set of plugs and plug wires so diving into that next.
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NIevo
Full Access Member
Glad you figured it out but a little concerning that they didn't notice that when tuning.
Good point, I'm now wondering about that myself.
992dr
Full Access Member
Thieves suck, sorry you had to go through that.
Yikes, how could they have missed that?
Hopefully they logged and saved your factory tune file.
Yikes, how could they have missed that?
Hopefully they logged and saved your factory tune file.
Tell me about it, for me that's just life take your licking and keep on going the only thing that sucked to me was I don't know who did it because I believe in an eye for an eye lol but thankfully they did have a stock file and just modified it and it's seeming to be better and is slightly better on gas. Not like it was but I could contribute some of that on the aged components needing replacement.
