I am new to this web site. I have a 12 valve cummins. On somedays when the temperature is just right my truck will run perfect. When it gets to hot or to cold the truck will act like it lost its power. What could be wrong with it?

 

Does it seem to happen during the summer and winter months,or all year round?

 

Mainly when it gets really hot and when it gets about 50 degrees otuside. It runs great when it is about 65 to 70 degrees outside.

 

diesels do not like the cold so, that could be a small warm up issue. All motors loose power when its hot. I like towing at night because its cooler and power and mileage go up

 

mine runs good when its hot or warm i get 25 miles a gallon running around town,when its cold my tranny dont shift right so my mileage goes down

 

my 12v HAS to warm up for a solid 15 mins or it is a dog. it is a good practice to do so eitherway, on any diesel.

as far as power and fuel economy on a hot day, keep in mind air density plays a big part in a boosted engine's performance.
hot air is inefficient and less dense.

down here we mostly drag diesel's at night, as +100* air temps during the day can cramp our style

 

ive noticed up here an 90* days my cummins losses just a tad bit of power but not enouph to totice as for cold i wait till the thermostat pops and driver like i stole her but i also have a crap load of performance upgrades that may play a small roll in that

 

Come on up where its cold and see how crappy these things run. I dread winter.

 

winters sucked up north, thats why i moved to texas, only 2 weeks of crappy cold then back up the charts we go!!!

 

granbury. its nice up there. days are nice right now, but gets stick and cold over here in the tyler- carthage aread

my truck hasn't been off in about 4 days so it wouldn't even know its colder up here