Won't go past 2k rpm

[jerryrigxj]

My xj I bought has a weird issue with not going past 2k rpms and when I try to push her past it she stutters and pops out the exhaust like she's going to die never stalls just her rpms go from 2k to 1k and pops I've replaced the throttle position sensors idle air control valve put a new fuel pump cause the old one was whirring so loud you could hear it in the car and people following me could hear it the new pump is now making the sound just slightly quieter have even put a new crank position sensor kinda out of ideas on what could be stressing the fuel pump out and causing the limit in rpms the 2k rpm limitation has persisted even after swapping out the noisy failing fuel pump

 

[Tim_MN]

Year, engine, transmission, modifications?

Have you checked for any pending or active Check Engine Trouble Codes? Have you tested the fuel pressure? Have you tested the engine sensors? Cheap crappy replacement parts are very common. They can be out specification or even faulty right out of the box.

 

[jerryrigxj]

Year, engine, transmission, modifications?

Have you checked for any pending or active Check Engine Trouble Codes? Have you tested the fuel pressure? Have you tested the engine sensors? Cheap crappy replacement parts are very common. They can be out specification or even faulty right out of the box.

Shes a 91 with the 4.0 and the auto trans she doesn't throw a check engine light however when I do the key trick I get a code 21 followed by 55 I've ended up replacing everything important w Mopar parts only thing left is the 02 sensor

 

[Rob Mayercik]

Don't have the FSM for my 92 handy right now, but according to this link:

21 = O2 sensor signal not changing, sensor possibly falied
55 = end of readout (not actually a code).

 

[jerryrigxj]

Don't have the FSM for my 92 handy right now, but according to this link:

21 = O2 sensor signal not changing, sensor possibly falied
55 = end of readout (not actually a code).

i believe it to be original too so it checks out w the mileage on her I eventually want to put a 4.7 stroker in her