1998 Jeep Wrangler 4.0 manual trans

jeep
wrangler

#1

I have a 4.0 6 cyl. Jeep wrangler manual transmission. When the jeep is driven in higher RPM close to redline the jeep sputters a bit (doesn’t have full power at or close to redline). Is this a governor or does the jeep have a problem?

please help if you would.

I do not redline often at all. however i live in the mountains and need to travel up steep pass for 1-2 miles every few months.


#2

This engine is rated at 180 HP @ 4500 RPM. I would expect the rev limiter to be at approximately 4800 RPM. This old push-rod six is not a high revving engine.

It is often necessary to down shift to maintain speed while climbing a grade however I am not comfortable with maintaining an engine speed over 4000 RPMs, these grades can continue for 10 miles, it is better to reduce your speed.


#3

Make sure your plugs & wires are in good shape. Try replacing the ignition coil. My son’s Jeep, same year 4cyl, had a similar problem, under high load the engine would bog down. A new coil fixed it, inexpensive and easy to change.


#4

This is an old Jeep with, as the others say, a low revving straight six. It could be nothing more than old, weak valve springs that can no longer close the valves at near redline. That would cause stutter and misfires. Stop revving that high. You could change the springs but this engine wasn’t made for that. It was made for torque.

You really only need to be past the torque peak, not the HP peak. I’d guess that would be about 2500 RPM or so. Torque moves the Jeep and if you are past the RPM of maximum torque (say 2700 RPM), then if you hit a larger grade, the drop in RPM will INcrease torque available as you slow.


#5

Thank you for the feedback, I’m all very good advice. It is only read that high for a little bit less than a mile to get up to get up the mountian.

Sounds like it could be a coil


#6

How high? When you reach the rev limiter the PCM will switch off the fuel pump relay to control the engine speed. You will get a nasty lean sputter warning you to back off.


#7

Two problems maybe? Engine sputtering due to an ignition miss or fuel deprivation and possibly clutch slippage.


#8

Rpm are around 3500 to red line so that is why I am wondering what to do


#9

3500 RPMs is far below red line, if you have a performance problem at normal engine speeds it is time to begin diagnostics.


#10
i live in the mountains and need to travel up steep pass for 1-2 miles
Normally-aspirated engines lose power at high altitudes. The higher you go, the greater the loss.

#11

This is true, but the same problem happens around town. It is always over 3000 rpm that the engine hesitates. I’ll try some of the suggestions here