Changed out engine and transmission from 2007 Dodge Grand Caravan with a low mileage engine and transmission from 2005 Dodge Grand Caravan. Drives fine in and around town, stop and start driving. On long distance, 20+ miles it goes into "Limp" mode. 90,000 miles on engine and transmission. Two mechanic shops have tried to "fix" this and they can't figure out what is wrong. They keep thinking it is the computer and is an "electrical" problem. Replaced the computer, nothing. They tried other stuff and nothing. I think it is a transmission problem. It only happens when the engine and transmission "warm" up. I haven't been able to use this car for a year and a half. I drive 100 miles a day. It is my "backup" car. I need to get this car back on the road. Any help would be greatly appreciated.
Well the problem is you used an older engine and a newer car. Odds are the computer. Software is not compatible so wouldn't even matter if you swapped a computer because you have an engine from an older car so it might not jive with an computer and a newer car. But if you put the computer from the older car in the newer car, it would not work right because they would be different wiring the different sensors in the system. This is why I advise people never to swap modern car engines unless it's the same exact vehicle. Good luck though, but if somebody brought me one of those I'd hook up my computer and see what was going on. But I probably wouldn't want to really mess with it seriously because it may be unfixable
