GMJunkie7

I did have a code for the trans temp P0711/ P0700 When the codes were there, the shifting was very erratic. I cleared the codes to see if they would return, and they have not. It's been almost 3 weeks since those codes popped up and then were cleared. Shifting has returned to normal, but the trans temp display sometimes bounces +- 5 to 7 degrees every few seconds. I have a heard time believing the NGK plugs could be at fault, but again, there's not much else it could be I suppose.

Unfortunately I dont have the old plugs, otherwise I would do just that. I tossed them with all the packaging from the other components. I did think about the brake dragging, but I have checked the rotor temps after a long ride and don't seem to have any big differences in temperature. I'm also not putting any more foot into the pedal, it just seems like as soon as i rest my foot on the pedal the instant MPG meter drops to below 10, even during slow acceleration. I will for sure try the MAF sensor and report back. Not sure how to look into the data log but I am sure I can figure it out. This may make the most sense to me. its funny, sometimes it seems like all of a sudden I am getting better gas mileage again ( judging by the instant meter) and I jump back to the trans temp reading and it shows a steady temp. Almost like sometimes the sensor does behave correctly, and when it does, that's when the mpgs go back up, but it could just be my imagination... that instant mpg meter doesnt tell the whole story.

Hey all, Here's the story. I've got a 2016 1500 silverado highcountry 5.3 that has for the most part been good to me ( except for the hard shifts and transmission issues alot encounter) Recently, I gave her the 100k mile tune up. As part of this, I did brakes, and spark plugs. My local Advanced didnt have AC Delco, so I used the "correct" replacement NGK plugs. As part of the brake install ( since I tow I installed powerstop brakes) I had to do a brake in procedure involving accelerating to 40-50 mph and doing some hard braking then light braking, then 10 minute ride to cool them down. During this brake in procedure, I got a check engine light. Turned out, I got a bummed spark plug on my cylinder 7. No biggie, replaced the plug and went on my merry way. However, since I replaced the brakes and spark plugs, I have gotten HORRIBLE MPG. I used to average about 22 on the highway, 16-17 city, and 18 ish overall. Now I am lucky if I'm getting 15 on the highway after shes warmed up and I've been driving for 15-20 minutes at a steady 65-70 with cruise control on. I am ALWAYS babying the gas trying to maximize fuel economy, but no matter how easy I drive, I still get horrible gas milage. I do live in Nebraska, and it has been cold here... but this issue started while it was still 50-60 degrees out, and I have never gotten this bad of gas milage in the winter. Sure it might drop down to 19 on the highway from 22, but never down to 14. One additional thing to note is about 1-2 weeks after the tune up, I did recently get a check engine for the trans temp sensor. I cleared it, and it has yet to come back, but I have noticed the trans temp on the dash is hopping around quite a bit. Could this trans temp sensor have anything to do with the poor MPG? Maybe the trans isn't behaving as it should due to this faulty sensor? Think the spark plugs could be the problem? I used to get north of 450 mile per tank, and recently have barely been able to get 320. Any Ideas would be appreciated!