Cooling and high idle bad mileAge issues

I have a 98 with the 4.0 and tge only motor mods being apn header and electric fan kit from ff dynamics. The cooling issue: it runs fine while driving down the interstate in town but it runs hotter when going up hills like 220 and as soon as I take it off road it skyrockets I have changed the water pump thermostat even put in a 180 both radiator hoses the radiator itself is only a couple years old I'm stumped the high idle mileage issue: when u start it up it runs fine and drives fine then it warms up and while your driving at higher speed you let off the gas to slow down and the rpms only drop about 500 once it starts acting up it'll do it with it in neutral too the only wY to make it idle back is to floor it for a second it's only getting 12mpg it should to better than that seems like it should have more power too sensors I have changed are 02 map tps CPs done plugs cap and rotor any help would be appreciated

As to your coolant issue. Think about it this way, when running down the interstate you have lots of air moving past. When going up hill it decreases, when offroad it is lower still. Air flow seems to be the variable that is giving you trouble. Check your IAC for the idle issue. Your IAC allows a metered amount of air past the throttle plates once they are closed but it should close once throttle plates open. Also check to see your throttle plates are not gummed up, keeping them open slightly when you close throttle.

I had the tripple threat fan kit and ffdynamics radiator and had the exact same issues with temps. A Hesco high flow pump didn't help. RunCool XL hood louvers didn't help. I read a couple post in random overheating threads where people who had only the ffdynamics radiator had the same problems so I bought the best radiator money can buy, the 600 dollar two row griffin radiator quadratec sells. Now my temps never go over 210 even in 105 degree weather with the AC on going up hill. I believe the fans don't put out enough airflow to keep our Jeeps cool, I actually don't think there are 10" fans anywhere that flow enough, and since I have seen people post with issues using just the radiator I don't think it is efficient enough either. With the ffdynamics radiator I had a average of 20 degrees difference from side to side on the radiator, with the griffin I checked it a couple weeks ago and it was a 40 degree difference across it so it is much more efficient with the same airflow.

So the cheapest way to fix your cooling system is to go back to stock, and I'm not even sure if you went with stock fan with the ffdynamics radiator it would work. The only way I would keep the electric fans is if you bought the griffin radiator.

My ac system is completely toast so if I deleted the whole system including the condenser do you think that would help with air flow

Ac system removed problem solved

Boom1699 said:

Ac system removed problem solved

Click to expand...

Not really... I'd say the problem is just masked now. You'll see it again next summer.

Low speed means airflow issue... you swapped in an efan that isn't pulling enough air

IslanderOffRoad said:

Not really... I'd say the problem is just masked now. You'll see it again next summer.

Low speed means airflow issue... you swapped in an efan that isn't pulling enough air

Click to expand...

There it is...

I had a long running issue with my heat climbing and then I checked out my fan clutch... nasty gunked up and old. Replaced it (inexpensive) and now she maintains normal temps.