On 26 May 2011, my girlfriend and I stopped into Carmax of Hartford to upgrade our 1998 GMC Sonoma (2.2L, 2WD, 4spd AT, 182K miles) to a truck that would serve my business better. While looking at their trucks with a sales representative, an appraiser came by and took the keys to our truck for a quick road test. 25 minutes later, the sales representative receives an email stating our GMC was only worth $250 because of "transmission shifting issues". Being an automotive technician for 10 years, I assured her he was mistaken, and asked to speak with the appraiser. When asked to explain the said issue, his comment was "Well, I really pushed her when I left here to get her up to forty, and she shifted real hard from first to second, indicating a transmission issue" .. I was shocked that he would admit to abusing my truck, but felt that maybe he just used the wrong terminology. Back to the sale rep., I was asked if I'd like to trade my GMC, and I declined knowing I could privately sell it for over $2K. On that decision, my girlfriend spent the next four hours looking at medium sedans, and settled with a 2006 Chevrolet Impala, financed, and purchased the extended warranty. After thank yous, hand shakes, and such, we get back to our GMC, and started her up. Right off the bat, the idling was rough. My girlfriend noted as much, and I thought maybe it was just the bad gas we purchased earlier that day still running itself out of the system. As I'm pulling out of the lot, my truck stalled while in idle. I restarted her, and the idle became rougher. Frustrated, I continued down the road (25mph speed limit) and pulled onto I-91 South. Halfway down the on-ramp, at about 40mph, the truck's RPM range dropped so fast the truck stalled out, and we were stuck on the side of the road for 3hrs. I called Carmax to speak with the appraiser, but the business was closed for the day. I was beyond frustrated. I crept the truck home, stalling out at every light, and finally pulled to the driveway, where the truck stalled one last time, and refused to start again. I am extremely aggravated at the mistreatment of my vehicle. I called Carmax the next day, and spoke to three managers, who each gave me the generic "a truck with that high of mileage, you cannot be sure it was our appraiser's doing" before I finally got a manager who stated that the appraiser "has worked for her for many years, and has test drove many nice vehicles" ... I told her that owning my own business, I am well aware of companies defending their employees and did not expect to get any cooperation. I was told that a master technician and a manager would show up to my house and look at the truck to determine if it was negligence of the appraiser's doing. I was greeted with respect, and the master tech. scanned my truck, found it to be running lean on cylinder one, which concluded that it was a spark plug issue and therefore not the appraiser's doing. When I worked on the truck today, I pulled plug one out, and found the spark plug gap to be crushed, and the two points nearly welded shut. I also discovered plug three's gap to be pushed in slightly, while two and four have scrap indications. My diagnosis is that the appraiser slammed on the gas and the RPMs redlined, causing the pistons to hit the spark plugs, which is what will happen. I am appalled at the service I received after politely, and proffessionally filing a legit complaint. It's unfortunite that I purchased a vehicle from them before knowing what they did to my truck. At least their appraisal is right, the truck is worth $250 now.