i have a 91 ranger xlt i just bought two days ago. its a 5speed 2.3l and I did a standard tune up but before and after was having problem with hesitation.

what I did: fuel filter sprak plugs wires(still have to get the infamous driverside - im finishing this today), pcv, cleaned tb, took apart and cleaned maf and ics, oil and filter, air filter, and checked for leaks vacuum and fluid. I'm doing the thermostat today or tomorrow b/c the interior gauge comes on and off(does not seem to the overheating and has fluid in both tank and radiator), I also did seafoam in the intake crankcase and fuel. the fuel filter had a dark tarnish look to it when I replaced this. plugs looked ok just maybe a little hot but not burnt up and no residue.

Whats wrong: 1st you notice a slight unburnt fuel smell( i believe the manifold is a little warped) the main issue is that when u drive for about 10 mins (outside heat index 105) it begins to hesitate under acceleration unless your extremely soft on the pedal. It gets worse as you continue to drive. my initial thoughts where that the fuel filter needed to be replaced or the maf( maf is good and filter is new). once it starts these troubles if you floor it to overcompensate it seems to almost try and stop. the a/f mix is unable to be changed to my knowledge. the last thing i can think of is the fuel vaporizing from a line getting to hot, but i followed this with my hand to find nothing out of the ordinary. it really feels as if its getting too much fuel and bogging out.

I'm a nissan man and fan for life, someone please convert me because this little ranger has much potential/

 

I had something like this happen with a Jeep 4 cyl. I have and it turned out that the catalytic converter and muffler were clogged. The insides of the cat broke up and clogged the muffler and when it got hot and developed back pressure the engine would not run. If you feathered the pedal you could get it going but if you floored it, it died. Something to check cause it looks like you checked everything else. You have to get air out if it comes in.

 

this sounds a lot like what i am dealing with really dont think its the fuel pump because you can smell it running rich. im in an area where there are no emission standards any ideas for a cheap exhaust for me to put on. i dont want a trashcan sound and im really wondering if i should even put a cat back on it or just run pipes and a muffler. what are your thoughts. I also changed the TPS today and finished those badly place spark plugs on the driver side. the fuel is not getting hot either so its not from vaporizing. runs much better until it warms up and then i can barely get it past 2000 rpm, and if i throw it in neutral to floor it it still bogs with no load.
thanks to all

 

I don't know where the O2 sensors are on a 91 Ranger but if there is one after the cat, you probably have to replace the cat to get the temps into the correct range for the sensor to send the correct signal voltage to the computer. Look at the exhaust and see. If there is no sensor after the cat, you are home free, just pick out a muffler you like and get pipes to fit and bolt them up. It made a big difference on the Jeep when I did the exhaust.

 

ok its not the muffler or the cat, im thinking maybe o2 but whats happening know that everything routine tune(fuel,plugs, wires, seafoam,injectors and tank and intake, pcv) it idles higher and feels stronger until it gets warm about 10 mins in and starts stumbling hessitating under load or acceleration and its not the maf and i just replaced the tps and cleaned the ips. any ideas would be great sooner the better

 

This is a wild shot. A coolant temp sensor that is defective could be sending incorrect temp info to the ECM that may be trying to control fuel amount based on wrong info from sensor. Before you go replacing it based on this wild shot there are tests that you can do to verify this. I would get a manual with the specs so you can do this AND have it for further reference if needed.
Test- don't guess! hanky

 

Its not the TPS, or the O2. Spark is good on all 8 plugs, good airflow, no vacuum leaks that I've found. Cat. is ok along with clean TB and a good temp. sensor.

Symptoms: bog when accelerating or under load (engine is warm), smells of unburnt fuel, (while bogging)popping and rpm decline if the foot is put down aggressively or hard, if you turn the truck off and back on u reset the sensor (need to know which) and it goes until it decides, high rpm (1500-2000) when in neutral but when reset it goes back down to 1000.

Any constructive thoughts relevant and accepted. Thank you very much for your help.