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Intermittent lack of power

SouthSeaPirate

NAXJA Forum User
Location
Florida
Can only feel on accel and it is very minimal.
It feels like being in too high of a gear. Give it throttle and you will accel but not as fast... Then all of a sudden I get normal power.
Again tho, it is very minimal, nearly to the point where I question myself if it is really happening, very seldom, and only for a couple of seconds.

Happened before and after engine swap.
Hot or cold.
Plugs are new, alt new, all fluids new, etc

2001 4x4 manual
 
Could also be a delayed downshift.
 
You could also grab a scan tool with live data functions and watch fuel trims. That might provide some insight.
 
Auto? Locking torque converter?
 
intermittent bad reading coolant temp sensor or o2 sensor ?
 
intermittent bad reading coolant temp sensor or o2 sensor ?

My first guess is a bad spot forming on the TPS internal contacts

Map Sensor Vacuum line starting to go bad

Cap and rotor getting worn?

MAP sensor and TPS sensor are the two key initial data sensors for fast acceleration signal to the computer
 
So. everyone is giving great ideas.
But the most important thing to keep in mind here.
This is an engine.
You have.
Spark.
Fuel
Compression.
Exhaust.
the quick and easy way to check all of these are below.
For spark. Grab the wire off a plug. ground it off. make sure spark is blue/white. if its yellow you have an issue.

fuel pressure. I highly recommend making a perm fuel pressure gauge. https://www.jeepstrokers.com/forum/viewtopic.php?t=536


compression is just a compression test. ON ALL CYLINDERS.

and finally exhaust. A blocked cat could be a possibility. I would check everything above first. because you have to remove it to check.
hope this helps
 
dying coil and/or fuel pump will both make it cut weak

If been wanteing to switch over the the minivan external coil pack.
As well as having a fuel pressure gauge

Seems like a good excuse

Recommendations?

I like ehall's suggestion. Unless you have a way to see the ignition waveforms with a scope, I would just replace the coil pack with a new Mopar one. I have had a 2001 for 13 years and a 1997 for 3 years. In all that time I have had to replace a coil on the 1997 but never had a problem with the coil pack on the 2001.

My first guess is a bad spot forming on the TPS internal contacts

Map Sensor Vacuum line starting to go bad

Cap and rotor getting worn?

MAP sensor and TPS sensor are the two key initial data sensors for fast acceleration signal to the computer

A worn TPS can do all kind of weird things too. When mine was failing the engine would rev up when I was coasting off an exit ramp. A couple of days later it actually felt like the engine was cutting out for a split second and then coming back. Here again, I suggest Mopar.
 
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Few things worth checking. Exhaust manifold leaks, fuel line leaks and FUEL PUMP LEAKS. I capitalize that one because often cuts wont go clean through and will lead to inconsistent power as opposed to stalls or no start
 
Thanks for all the suggestions everyone!

True, I have the coil pack over plugs, so I cant pull to check spark.
Again, this is so intermittent that checking this way, even if I could, would be pointless.

The engine is a fairly recent install, with new gaskets top to bottom. Compression is fine.

I can deff hear a leak in the exhaust, done by an exhaust shop... At least it better be that part they did cause I did everything I could to make sure the exhaust wouldnt leak at the head. Including what I was told to be the best gasket and used copper spray on both sides.

Note that I have an 01 and that the O2 sensors are up in the header. So not one of those with the crack at the collector and the O2 after that getting bad readings.

I have had every so often a high idle when coasting to a stop. Sometimes I have to tap the gas and it goes down (this fixes it every single time). This hasn't happened in a while tho. So possibly TPS?

Ill deff get it on the laptop asap
 
Thanks for all the suggestions everyone!

True, I have the coil pack over plugs, so I cant pull to check spark.
Again, this is so intermittent that checking this way, even if I could, would be pointless.

The engine is a fairly recent install, with new gaskets top to bottom. Compression is fine.

I can deff hear a leak in the exhaust, done by an exhaust shop... At least it better be that part they did cause I did everything I could to make sure the exhaust wouldnt leak at the head. Including what I was told to be the best gasket and used copper spray on both sides.

Note that I have an 01 and that the O2 sensors are up in the header. So not one of those with the crack at the collector and the O2 after that getting bad readings.

I have had every so often a high idle when coasting to a stop. Sometimes I have to tap the gas and it goes down (this fixes it every single time). This hasn't happened in a while tho. So possibly TPS?

Ill deff get it on the laptop asap

It sounds like you have a Unicorn Jeep. Possibly modified by a previous owner. All 2001 models were California emissions and should have mini-cats and 4 O2 sensors. For those that didn't want to replace the minicats, and could get away with removing them, without being detected, because its still against federal law, they would use a 2000 federal emissions Y-pipe and swap in a 2000 federal computer.

Since the sensors often fail/open up when hot but test good when cold/cool, diagnosis can be a bit complex. For testing the TPS all you should need is an analog meter or scope and make sure it reads smooth through the throttle range.

Its not a bad idea to change engine critical sensors every 5-10 years and keep the "spares" under the drivers seat.
 
Thanks for all the suggestions everyone!

True, I have the coil pack over plugs, so I cant pull to check spark.
Again, this is so intermittent that checking this way, even if I could, would be pointless.

The engine is a fairly recent install, with new gaskets top to bottom. Compression is fine.

I can deff hear a leak in the exhaust, done by an exhaust shop... At least it better be that part they did cause I did everything I could to make sure the exhaust wouldnt leak at the head. Including what I was told to be the best gasket and used copper spray on both sides.

Note that I have an 01 and that the O2 sensors are up in the header. So not one of those with the crack at the collector and the O2 after that getting bad readings.

I have had every so often a high idle when coasting to a stop. Sometimes I have to tap the gas and it goes down (this fixes it every single time). This hasn't happened in a while tho. So possibly TPS?

Ill deff get it on the laptop asap

Leak? Check real hard for a vacuum leak!!!

High idle, also possible TPS issue for sure, but check the floor mat too, make sure it is not riding up against the gas pedal cable. It is an issue for me at times on the older rigs (floor mat).

TPS is a very common wear item that messes with throttle speed and power control, and at times shifting. They are easy to replace and cheap.
 
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