It's only got 100k miles on it. Is that old and worn out for a Chrysler product?

 

I am still chasing this issue a little bit. I did replace the IAT sensor and the mileage seems to be improving a little bit. I had just a quick "dummy" type question about a coolant temp sensor. I know it has quite a bit to do with fuel mileage on some vehicles. My temperature gauge seems to work fine and the cooling fans cycle as they should. Can the coolant temp sensor be bad if those are working fine? Is there two separate coolant temp sensors on the 3.3 Caravan?

 

I replaced the MAP sensor and it seems to run much better. I am still trying to chase down the highway issue. I get to even the smallest of hills and I can feel the engine lose power a bit then it just downshifts. It doesn't even try to go up the hill. And I mean they are SMALL hills! Even going up hills in the city it always feels like it's in the wrong gear or it's severely underpowered. On flat ground, it performs great but it has picked up a bit of a hesitation at load. Get on a highway hill and it falls flat on it's face unless it downshifts. Sometimes it drops out of overdrive, sometimes it goes to 3rd, and sometimes on occasion it drops all the way into 2nd gear and almost tachs to redline to make it up moderate hills! It fees like it can't get out of it's own way on hills.

I tried driving my father's 2002 GC with the same exact setup as mine engine and transmission wise. His motors up the hills on the highway no sweat. And his has 175k miles! Something is definitely wrong here.

 

Sorry to hear it. My 2002 @135k miles GCS gets 18.2 Average and is driven like a borrowed mule.

I see a trip to a dealership and a connection to a factory diagnostic machine in your future.
And then a compression test may be suggested.

We all are good about responding here but when it comes to hidden gremlins like this one I would shoot to the dealership in a heartbeat.

Good Luck, Can't wait to hear what you find.

 

I also get 11.6 to 12 mpg driving in stop n go Chicago city traffic. But on the hwy at 70 mph I get 27.1 mph avg. Change your air filter to a new FRAM Tough Guard series! A new air filter improved my mpg! See: http://forum.chryslerminivan.net/sho...g-on-a-4th-Gen! - My post in another forum!

 

A clogged catalytic converter is a definite possibility, you would need a way of testing backpressure or a direct way of measuring temperature to make a proper diagnosis. With neither of those at your disposal I suppose parts swapping would be a valid course of action - can you grab another catalytic converter from a wrecker or something to minimize the cost of attempting this fix?

I dealt with a clogged cat on my sister's mailbu at 210,000km, I'd say it felt like you were dragging an anchor that was cut free every time you were coasting. It'd roll along just fine but it struggled so much to get up to speed or on a hill. On her car we were able to remove the front O2 sensor (as the exhaust gasses were directed against a heat shield and wouldn't burn anything as they exited) and took it for a test drive - it felt like a completely different car, so much more power. We fitted a replacement cat and replaced the muffler since it was full of pieces of the catalytic converter and it was fine since (2 years ago).