It was a normal day in our sleepy town. "Maw" and I were just finishing our morning brew, when the Catera rolled into our shop parking lot. Morning John, We both greeted him. Nice day isn't it, no snow, sun's out. What more could we want in December. John grumbled back yeah. I got a weird problem here. It's the wife's car and she's madder than a hatter with "Betsy" out there. She was driving down the highway and tried to pass the smelly recycling truck she was following. As she accelerated to pass, at about 120+ kph Betsy started to loose power leaving my wife on the wrong side of the highway with on-coming traffic. Slithering back-in behind the truck, she came home, sparks flying in all directions, mainly at me!! John said that his mechanics had taken a look at the car, hooked-up their scanner and found nothing wrong. You are good at nailing problems...it's all yours. You got to help on this one, or I'll be in the "dog house" for Christmas! And so he left the car with us. I took the car out on a drive test after he had gone. Just as he told me, at around 120+kph it felt like I was towing that Recycling truck behind me. I checked some of the scanner readings, nothing unusual, except at about 2900rpm the engine started delivering less fuel than it should. It felt to me like a traction control system problem. I pulled over, got out and inspected the tires and I noticed different sizes on the front and back. Hmmm...we are getting closer, I said...Switching my scanner into ABS/TRACTION system diagnostic mode, I proceeded down the road. At over 100+kph it showed speed difference between front and rear tires. The front tires were spinning slower than the rear tires. SEE (no problem.gif).
I continued to accelerate until at approx 124kph the power loss problem showed-up. The engine started reducing torque output SEE (problem.gif).
I drove back to the shop and phoned John. John, did you recently buy new rubber for Betsy? Yes, came the replay. You see my wife is one of those hard to buy for sorts. I presented her with 2 new tires for her Birthday. Great gift, isn't it. Why do you ask??? That's your problem. There are two different tire sizes - front VS back! Your car is rear wheel drive and the car's traction control senses the difference (rear spinning faster than the front) and thinks that the car is starting to loose traction at the rear drive wheels and reduces engine torque output by injecting less fuel in order to see the tires slow down...Dead silence at the other end of the phone. John, you still there? I heard a low groan, yeah I'm here. I tried to save some $$$ on cheaper similar close fit tires from Xxx-Mart. Not a word to my wife about this. I'll take it from here - thanks...