High RPM during acceleration 98 TJ

Wakeangel

Wakeangel

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Joined
Oct 3, 2019
Messages
81
Location
Chandler, AZ
The details;

TJ Sport six cylinder. 31-10.50's on original steelies. When it's stupid hot out ( currently 109 in Phoenix ) if I'm on the freeway and stomp on the gas the rpms jump up to about 4500 before the torque converter locks up. Though it actually seems like it's downshifting into 2nd because of the high rpms. This is especially present on long steep mountain roads. It will also do this on streets but because I'm only going 40 or so the rpms only go up to 3500. This issue seems to be temperature related because it doesn't do it in the morning.
Here's what I've done so far.

New spark plugs the recomended autolites.
New O2 sensors NTK

The engine temp is sitting at 210 on the freeway and about 208 off. This seems high to me because it used to run at around 195/200 ish. It has shitty cooling system parts but that's about to get overhauled with recommended mopar parts. I just finished doing the thermocure flush, which is outstanding by the way. It did a way better job than the prestone flush.

The catalytic converter is the original. Could this be my problem?
 
It should downshift (within reason) when floored. There is usually some RPM threshold where it won't downshift, but that threshold is typically 85-90% of redline in many vehicles.

You will get the most torque at the wheels at a given speed when the RPMs are closest to peak horsepower, which is around 4500 RPM.

I don't see a need to fight it, as you will get the most power in 2nd gear. I routinely let my other car (F150) downshift to 2nd gear at 70+ mph to climb hills.

210 is the proper engine temperature. Lower than that, and emissions and fuel economy tend to suffer. Much higher than that, and the engine suffers accelerated wear.
 
When was the last time you had your ATF and filter changed ?
You should check the color of the ATF; should look similar to cool aide.
IF the color has a brownish tint to it...; then it's time to have the ATF and filter changed.
A dirty filter or ATF could affect the system operation especially when it gets hot...
 
Before doing anything else check it's ATF level, your symptoms could be caused by nothing more than a low ATF level.

There's only one way to correctly check your 32RH transmission's level. Start the engine and make sure it is warmed up. Set the parking brake, then shift through the gears a few times and then leave it in NEUTRAL. With the engine still running and the transmission in Neutral check its ATF level.

You'll get an erroneously ATF level in it's higher than it really is if the transmission is in Park or if the engine isn't running.

The ATF needs to be at the full mark line. Not below it. It's far better to be slightly over filled than under fillled.

Low ATF will cause slipping. Make sure that's what is causing your slippage.

If it's low on ATF add ONLY ATF+4. If the bottle doesn't say ATF+4 in big letters on the front label it's the wrong.
 
The filter has about 8000 miles. I changed it last October, ATF+4 only. I check the fluid regularly ( engine at operating temp in neutral on level ground). I've had this Jeep for 21 years. This is kind of a new thing. It ran cooler with mopar parts. Which is why the temperature concerns me and why heat seems related. But if it's not doing the engine any harm I won't worry about it.
 
At freeway speeds it jumps to a little over 4000rpm. It seems as though it's shifting down into second. But it only does it on really hot days. It doesn't do it in the morning on the way to work. Just on the way home. When I lived in Oregon this never happened. Only since I've moved to Arizona and only in the summer. Though it will do it if I have cruise control on and I hit a steep hill.
 
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