'97 Montero overheats when pulling trailer

[jimnaz]

I know I need to look into this more but wanted to post this in case anyone has experienced the same or has suggestions.
*Sorry if post is long but wanted to cover everything.

Purchased this vehicle about 6 weeks ago so do not know a lot of history on it. I have had the lower oil pan and valve cover gaskets replaced, power steering pump gaskets/seals redone, replaced an axle boot and new air filter.
*I know not all of this applies to the following but this is what was done so far.

Up until yesterday the truck ran fine. Gets ~15 mpg around town. Only oil leak now is a very small leak at the back plug on engine. Would cost too much to fix and it is only a few drops.
I rented a 6x12 flatbed trailer from U-haul and loaded it up with stuff. I am confident that total weight minus vehicle was 2500 lbs. I am about 2 miles from highway and 1 mile on highway the Check Engine light came on. Temp and oil pressure gauge were still in the norm. I turned around and went back home. Called my mobile mechanic but could not get a hold of him. Checked oil and level was fine, no obvious leaves with oil or coolant. After looking it over some more etc, we tried the trip again. Engine light went off so I was hoping it was just some sensor messing up. About the same distance on the highway the check light came on again and this time the temp guage kept rising to "H". I turned around and took side streets back to house and temp slowly lowered back to the middle.

Upon arriving home I checked oil again (still good). Once cooled I checked radiator and level was fine and overflow was full. (Not sure where it was at before.) I finally got a hold of my mechanic. He could not come out but suggested I check my fan in case the clutch went out. When I first checked it appeared to spin rather freely. I then started it and let it warm up. Turned off and checked again and there was some tension. I could move fan but it would not spin.

Any ideas/suggestions that I could check on before taking somewhere for repairs? I will go and see if I can get any codes from that check engine light.

Thanks for any help

Jim

[jimnaz]

I just found out that the trailer weighs 2K empty. This would have put total weight minus vehicle closer to 4000lbs.

The error code read:P0306 misfire right cylinder

Would this have caused over heating?

[monty98]

I've pulled the Uhaul 6x12 trailers fairly easy with my manual 98 sport in the past quite a few times, I could see where some added strain on the engine might reveal issues.

Constantly getting a misfire I think will cause the engine to overheat, you could have a bad spark plug, you could have build up in the cylinder, you could have a bad coil pack. Each time that particular cylinder misfires the ecu will change the timing, usually retarding it, depending on which engine you have in your truck I don't believe Mitsu has a knock sensor so it could be pinging/knocking with the added stress and you wouldn't know it, that usually causes overheating too.