Hello. I just recently have had trouble with my ford ranger truck running like crap. I went and checked the codes on my truck and here are my results

ON THE (KOEO) KEY ON ENGINE OFF CODE...code85-canister purge ciruit failure.
ON THE ENGINE RUNNING CODE...code77 operator error (Dynamic Response/cylinder Balance Tests)

know systems my truck is giving me is , in the mornings first start and sometimes during the mid day. when i go to take off the engine seems to like bog down giving me no rpm to drive away. so I will put it in nuetral and rev up the motor and it slowly comes back. I also have notice when first started the revs jumps up to 2000 rpm and then goes back down to around 900 rpms then goes back up then to normal operating rpms at around 1000

so has anybody have this problems and how can you fix these probles

 

77 is a test code so unless you were preforming the test ignore it.

on a 1991 3.0l the 85 code means the solenoid for the EVAP system purge canister is not working.
This will not cause your engine issues, the canister is probably located near the rad support and the solenoid will be attached to a hose on the canister.
EVAP system prevents gas fumes in the fuel tank from polluting the air.
Since it is an "emission" feature it will will turn on CEL instantly.

Because of your idle issues I would clean the IAC(idle air control) valve first.
It is on the upper intake by the throttle plate it has a 3 wire connector.
remove and clean.
Computer uses IAC Valve to set idle.
Once IAC is clean, warm up engine and let it idle, unplug IAC Valve wires, RPMs should drop to 500 or engine may even stall, either is fine, if idle doesn't drop then you have a vacuum leak, which can cause all sorts of issues including bogging and surges in idle.

Normal engine idle should be
1,500+ at first start cold, computer opens IAC valve all the way
Then idle should drop to 1,000-1,200 based on outside temperature, colder = higher idle
As engine/coolant warms up the idle should go down, target idle is 700(manual trans), 800(automatic)

Since idle is changing I would think the ECT sensor is working.
ECT(engine coolant temp) sensor is used, ONLY by the computer, to set choke mode or warmed up mode, these rarely fail, but not never.
ECT has TWO wires
Dashboard gauges temp SENDER has 1 wire, they look similar but are different.

I would also clean the MAF sensor, it is the main sensor for computer to use to gauge the air/fuel mix.
Google: clean MAF sensor

Dirty MAF causes bogging and rough running

 

Hey RonD, Thank you for your reply back and the excellent description/understanding of what the codes mean and also what I should do first. and that is start by cleaning my IAC VALVE AND MAP SENSOR
I'm off to my local auto parts store to purchase the cleaning stuff. I will let you know the outcome of tonights task in my reply tommorrow morning. Again thanks for the help

 

1991 3.0l should have a MAF(mass air flow) sensor.
MAP(manifold absolute pressure) sensors were used on earlier models.

You will also have a BP(barometric pressure) sensor, similar to MAP in that it compensates for altitude, mountain driving, these rarely fail and would cause rich or lean codes on both banks