So i am going to appoligize upfront that this might get a little long.
I replaced a engine in my 1990 cherokee limited that was to have been a weekend prodject (LOL). after getting the engine running there was backfiring and hessitation when driving,almost like you are running out of gas. So we have replaced the plugs,wires,dist,icm,valve stem seals,head gasket,valve cover gasket,fuel filter,pump,regulator,injectors,coil,reset comp. Also for giggls we did the water pump and thermostate. So after all of that we are not able to realy drive due to the hesitation,the starnge thing is that if we unplug a vacume line on the intake it runs i little smother and the backfire is less but still feels like you are running out of gas, it also happens at any speed. So any ideas on what else to try that would be great. Thanks for all your help.

 

crank sensor?

 

i have one and we are doing that today. Thanks for that its a second opion

 

Whats your Fuel Pressure at the rail? it should be 31 PSI@ idle and 39 PSI when you disconnect the vacuum line at the regulator.

 

so after all the things we replaced the pcv line was plugged. so now it has lots of new PARTS.