Topic: Does your 2.5L run better some days than others?

[jwrape]

My dad and I both have 2.5L YJ's. His is a 93, mine is a 91. His has somewhere around 130k miles and mine has over 200k. It's really strange but there are some days that our Jeeps run like they have an extra 25hp or something. Yesterday on the way to work my Jeep was running like a scolded dog and I could actually hold my 85mph going up hill on the hwy which I usually have to down shift or just slow down to 65mph. My Dad's YJ does the same thing on some days. What is up with these motors. I would love to figure out what makes it run so good on these spiratic days.

[neale_rs]

Keep a daily log of relative humidity, temperature, and air pressure and you may find some relationship.  Probably high pressure, cold air and low humidity would be the combination that makes it run better.

[jwrape]

Keep a daily log of relative humidity, temperature, and air pressure and you may find some relationship.  Probably high pressure, cold air and low humidity would be the combination that makes it run better.

I beleive you are dead on because yesterday morning was a perfect temperature morning.

[dunklervogel]

Yeah I have this a lot.  I notice some days there is just no throttle response at all and other days I can accelerate in 5th gear like it was 4th.  Also, acceleration off the line seems worse some days compared to others.

 One thing I do notice is most of the times it doesn't have as much power when just taking off from the driveway.  If I'm doing some errands in town and driving for more than like 5-10 minutes it definitely feels different after it has been driven for a while.  I have no clue why this is.  Generally it is hard to tell when offroad because I'm not going very fast or driving a consistent speed to tell.

the temperate and humidity might have something to do with it but I also think the engine temp has a lot to do with it.. like the air/fuel mixture is different with a fully warmed up engine than it is when it is just heating up.

[jwrape]

I don't know if it makes any difference but I have been running a 165 degree thermostat or over a year now. I don't know if it helps or hurts but the Jeep doesn't get hotter than 165*

[neale_rs]

I´ve also noticed the changes in performance but have never had a good reference point to be sure. I'm pretty sure mine does not have a thermostat or it is stuck open.  In the winter it never gets to 195 but in the summer it can get up to around 200.

[jwrape]

I´ve also noticed the changes in performance but have never had a good reference point to be sure. I'm pretty sure mine does not have a thermostat or it is stuck open.  In the winter it never gets to 195 but in the summer it can get up to around 200.

Sounds like you have the factory thermostat in it. The factory stat is a 195*. When i got my Jeep I had the same one in it but my temp was getting around 210*. So when I changed it I wanted to go much lower to run cooler. I went too cold, I really need a 185 cause my heater hardly works. LOL! This winter was COLD. the Factory 195 is too high in my opinion, my floor boards were burning me up and the hood was always burning hot, I like the 165* in the summer cause with my electric fan I never have to worry about it over heating and also if my electric fan quits, as it has in the past, I can still drive home without overheating my Heep. The motor runs VERY cool. I have driven all day without a cooling fan before in the dead of summer. As long as I kept moving it was fine. Those little motors are realy tough.

[neale_rs]

Do you have an upgraded radiator?  Running cool without a fan really surprises me. Someday I'll get around to checking the thermostat but for now as long as it doesn't overheat it's fine for me.

[jwrape]

Do you have an upgraded radiator?  Running cool without a fan really surprises me. Someday I'll get around to checking the thermostat but for now as long as it doesn't overheat it's fine for me.

No didn't upgrade the radiator. It just runs cool with that thermostat as long as I'm moving a little and keep air flowing through the radiator it's fine.