Gareth

Hmmm that could be something to check out....

I have been dealing with an ongoing issue that has proved very difficult to resolve. ****Sorry in advance for the very long post!!!*** I have a 2007 Mack MR with a E7 350 and an Allison automatic. My truck has a crane mounted on it, and my problem is with the high idle when I'm operating the crane. The high idle uses the cruise control circuit so if I am going to use the crane I rev up the engine to 1100 RPM or so. The high idle will work properly for anywhere from a half hour, up to 2 or 3 hours, then it will trip an "electronic malfunction" light and kick down to low idle. The "electronic malfunction" light will turn off and everything will go back to normal if I drive the truck, usually as little as 30 to 50 ft. When my mechanic pulled the codes it said there was an irregular signal coming from the tail shaft speed sensor. (Allison transmission) My mechanic checked the tail shaft to make sure there was no play where it goes into the transmission, we replaced the speed sensor, the pigtail, the wiring harness back to the computer, and I had the computer reflashed at Mack. None of this made any difference. I are at a loss as to what to do. One more thing about the cruise control circuit is that if I set the cruise control while driving down the road it will not turn off when I press the brake, I have to turn off the cruise control switch. My mechanic checked all four of the brakes switches down by the treadle valve and they are all working fine. (I don't necessarily think that this problem is related, but it has to do with the cruise control circuit) Does anybody have any ideas?

I recently bought a 2007 MR cabover with the 350 hp engine and Alison transmission. I had a knuckle boom crane mounted on it for tree work. So the truck weighs about 40,000 lbs, and I often pull a trailer that might weigh 20,000 lbs. Right now, even without a trailer, the throttle response and acceleration is so slow it is almost a hazard to pull into traffic. I have had my mechanic go over the engine, and it seems to be working as it should. Since this was a garbage truck previously, I was wondering if they back off the power so the trucks last longer when the guys jump in them and mash the throttle every 3 minutes on the garage runs? I was thinking an aftermarket tuner or ecu reflash might be able to wake the truck up? Does that seem reasonable? What would you guys recommend as a reputable shop that does that?