Jerking at ~3500 RPM, ´99 4.0

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dgrobles

New member
Hi guys hope you're doing well. I would like to ask for your advice... I explain...

I have a '99 TJ with 4.0 and auto transmission... it has 105K on the odometer and about 4k since rebuild. My jeep is kinda my DD and runs about 40 miles a day, part in the city and part in highway... recently while I tried to pass a car on the highway I had to rev the engine reaching about 3400-3600 rpms and in this range I felt the engine like jerking and wouldn't go higher on rpm band... also, don't know if it is related but there is a point where even pushing the accel pedal to the floor you don't see any power from the engine (lack of power). It starts well w/o issues and idles ok with minimal variations...

Thinking in a possible low pressure fuel pump I already measured with a gauge and I have 45psi steady, even under acceleration (no load) so I think it is not related to the pump.

I have no clue were to find... and, I don't know if the job done on the rebuild has something to do, timing or something like that... Guys, any advice on were to look to find the problem?

Worth to mention that I have new header, new cat, new O2 sensors (NGK), new TPS (OEM), new spark plug, hi-power coil (D.U.I), wires, cables and distributor rotor cap, new fuel pump.


Thanks
 
Is it not accelerating or is the trans not dropping down a gear when you get on it? Check your kickdown cable and adjust it.
Otherwise back to beginning. Coil, plugs, fuel.


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I have a 3 speed transmission, so... on third when pushing down the accel pedal it does the downshift and reaching 3400 it starts jerking... but also it does it when in 3rd gear... so, don't think is related to the transmission.
 
dgrobles said:
I have a 3 speed transmission, so... on third when pushing down the accel pedal it does the downshift and reaching 3400 it starts jerking... but also it does it when in 3rd gear... so, don't think is related to the transmission.
Click to expand...

Not sure if the auto trans has one or not but my manual was doing the same thing and it was the Crankshaft position sensor mounted on the transmission. Make sure it’s a mopar or Napa part.


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