Strange power loss on highway

[TXAggieInGA]

Does anyone have an idea of what is wrong?

I have a 2006 Pathfinder with just under 100k miles that I bought used this summer, so I don't have much experience with it. This past weekend, I drove it on a 600 mile trip and it showed a strange symptom intermittently. When I was at highway speed, I would try to accelerate sharply to pass, and it seemed to slip out of gear, and the engine revved at 4,000 rpm. After I let up on the accelerator pedal, then I could slowly accelerate. It seemed that it would drop one gear, not two. I checked the AT oil level: it is normal and the fluid looks and smells normal. I'm not sure if this is related, but I've also noticed that the engine temp gage is varying from low to high (up to the mark that is about 75% up the scale). Also at one point, the AC stopped blowing cold air when I was driving in the afternoon, and then started working fine again, too. The AC worked great all summer. All of these symptoms are intermittent. I was never really able to correlate the occurences with each other, so I don't know if they're related.

[disallow]

Does anyone have an idea of what is wrong?

I have a 2006 Pathfinder with just under 100k miles that I bought used this summer, so I don't have much experience with it. This past weekend, I drove it on a 600 mile trip and it showed a strange symptom intermittently. When I was at highway speed, I would try to accelerate sharply to pass, and it seemed to slip out of gear, and the engine revved at 4,000 rpm. After I let up on the accelerator pedal, then I could slowly accelerate. It seemed that it would drop one gear, not two. I checked the AT oil level: it is normal and the fluid looks and smells normal. I'm not sure if this is related, but I've also noticed that the engine temp gage is varying from low to high (up to the mark that is about 75% up the scale). Also at one point, the AC stopped blowing cold air when I was driving in the afternoon, and then started working fine again, too. The AC worked great all summer. All of these symptoms are intermittent. I was never really able to correlate the occurences with each other, so I don't know if they're related.

Your temp gauge should definitely not be moving. Its a dummy gauge, meaning that it reads at the same spot of the gauge within a range of about 10-15 degrees F. If you see it starting to creep up, this is a sign of a problem!

I would start with the thermostat. Replace it, and see if the temp variation goes away. While your at it, make sure to check for any other leaky hoses, and the condition of your rad. Use the opportunity to do a drain and fill on your cooling system.

As far as your driveability concern, not sure if this is related. Sounds like a possible transmission issue. Drain and fill the transmission (you'll need 4 quarts of Matic-S or J $$$$) and that will give you a better indication of your fluid's condition.

Is your radiator trans cooler by-passed?

t

[TXAggieInGA]

This turned out to simply be low engine coolant. I found posts on other sites where people talked about the heater not working. It seems that pathfinders are sensitive to low coolant levels, as the air pockets will stop the flow to the heater core. I'm not sure why this may have affected the transmission except that maybe the engine was too hot which may have caused other things to shut down. Since I corrected the coolant level, I have not had any problems, including a 300 mile round trip last week.

G