I own a 2002 Peterbilt 387 and have had it almost 3 years. I have this weird problem that started yesterday. The truck has been governed at 70mph since I purchased it. Yesterday and today it intermittently governs me at 65mph. There does not seem to be any rhyme or reason when it starts/stops doing this. When it is doing it and I shut the truck down and restart it does NOT correct the problem. I'll just be driving down the interstate and it will intermittently change. There are no idiot lights that come on and it is running fine. All gauges are normal. It has been the same fuel since Monday morning. It is not sputtering or starving for fuel. The turbo pressure is normal. I was grossing 75,000lbs today and it pulled normal. Any suggestions? Bad ECM?
Just want to update incase someone comes across the same problem in the future. Hooked up to the truck with the Caterpillar software and found that the previous owner had the truck governed at 65mph. There was a driver reward feature enabled to give it an extra 5mph if idle percentage was below 35%. With the frigid weather, I was exceeding the idle percentage.
