bucking yj

[scott d]

i have a 91 wrangler with a 2.5 ,5 speed fuel injected an when i am cursing along it starts bucking no matter what gear im in ,i replaced the fuel pump,fuel regulator ,plugs ,cap an rotor,plug wires ,all the vacuum lines.the engine controller has 5 sensors ,the( cts) coolant temperature,the (mat) manifold air temp sensor,the (map) manifold absolute pressure sensor,the (cps) crankshaft position sensor,the (tsp) throttle position sensor. these are all ok. i can not figure this out.

 

[elwood blues]

Water in your gas???

 

[scott d]

thanks but this really bad

 

[elwood blues]

No seriously, do you get your gas from the same place all of the time? You could have water in your gas, if you have replaced everything that you say you've replaced the gas is one of the last things left.

 

[scott d]

no i cleaned the tank when i changed fuel pump

 

[gert]

I did not see your fuel filter listed I assume that went with the fuel pump? This is a most perplexing problem since you have eliminated all of the usual suspects

 

[scott d]

fuel filter changed was changed ,i put a gauge on the fuel rail an its right on spec.

 

[ken98k]

My 90 YJ does something similar but only at very slow speeds. I was told it had something to do with the clutch.

 

[gert]

does it do it when you lug the motor down

 

[ken98k]

does it do it when you lug the motor down

Yes

 

[scott d]

i found the problem ,even thought i tested the tsp with a volt tester an it checked out ok it was bad ,i changed it an it runs great . thanks for every ones input . scott