I was driving and started noticing a studder in higher rpm on highway and slowly started getting worse, to the point where it's now backfiring into exhaust and intake. 90 xj 4.0 renix 40 over
cylinder pressure is all good
all timing is perfect
New 02 sensor
New crank sensor
New plugs and wire and ignition coil and control mudule
tps is new
injectors still spraying good
Got good fuel pressure
New ecm
New distributor, cap and rotor
i need help bad its been down 6 months and ive lost everything since its gone down

 

Bad gas.
Distributor not indexed properly.
Timing gears not aligned.
Flexplate incorrect or falling off.
CPS misaligned.
Speed sensor dead/dying.

Did you do all of the Cruiser Tips?

 

exhaust not restricted ?

of course you did not throw away probably ok OEM sensors and trust cheap crap sensors, so try refit old O2 and crank sensor one at a time

(If replacing them did not fix the issue, they must have been ok)..its free

It is also possible you have junk in your fuel tank that restricts the fuel pump input

 

Check the wiring bundle from the O2 sensor back to the firewall
Specifically where it turns down from the intake manifold.
.

 

distributor and all timing components are correct issuebstsrted before i replaced, new flexplate its good my third ive replaced crank timing mark lines uo with tdc and distributor. Never thought of speed sensor howbdo i check that

 

what am i specifically checking on the wiring

 

i blew out fuel lines but i did not pull tank and i kept most of old parts.

 

 

Have you found any solution to that?