Cant figure out why 1991 gmc sonoma 4x4, 4.3 v-6 doing weird things 'sometimes'

when im driving along for sometime my truck will start to become sluggish and loose power .A hill that i usually fly up in 5th gear ill have to downshift to
4th to make it up the same hill.It sounds and feels like im driving a big diesel by the way it hesitates when shifting.It will do this for a couple of days and then maybe on the third day ill go out in the mourning and it will be working great and ill drive it for a few trips and it starts all over again.It eats gas when it runs like this as you can imagine.The truck works really well when it is running normal. Loads of power and really goodon fuel too.it seems to do this when it gets warmed up but the gauges are all reading good. I WOULD REALLY APPRECIATE SOME ADVICE ON THIS BECAUSE ITS DRIVING ME CRAZY.I have some ideas of what it could be but dont have enough cash to try everything by hit and miss.(maybe coil,air and fuel mixture,changed 02 sensor already)
yours truly confused
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

and loose power .A hill that i usually fly up in 5th gear ill have to downshift to 4th to make it up the same hill.It sounds and feels like im driving a big diesel by the way it hesitates when shifting.It will do this for a couple of days and then maybe on the third day ill go out in the mourning and it will be working great and ill drive it for a few trips and it starts all over again.It eats gas when it runs like this as you can imagine.The truck works really well when it is running normal. Loads of power and really goodon fuel too.it seems to do this when it gets warmed up but the gauges are all reading good. I WOULD REALLY APPRECIATE SOME ADVICE ON THIS BECAUSE ITS DRIVING ME CRAZY.I have some ideas of what it could be but dont have enough cash to try everything by hit and miss.(maybe coil,air and fuel mixture,changed 02 sensor already)

TBI or CPI?
Doc

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
hey doc its tbi
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Ok,
If she's eating gas she's running way rich, which will cause the lack of power/hesitation. It's not spark related as a failed ignition component wouldn't cause her to run rich, just run like shit.
First place I'd look, seeing as how the problem is intermittant it the CTS (coolant temp. sensor) and make sure the connection is snug and that the terminals, connecting pins and wires aren't corroded. CTS is located right beside your waterneck on the intake manifold, it'll have a 2-wire connector on it (usually yellow and black wires).
Second, I'd run a bottle of Chevron Techron thru it to clean the injectors and make sure one isn't sticking open due to gum and varnish buildup.
Have you scanned the ECM for codes yet?
Doc

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
i will try the cts and get back to you and i have not run the codes. It makes sense about the sensor and i do have intermittent problems with running rich . i replaced the o2 sensor and it seemed to help but it still does it when i run her for longer periods.i really appreciate the info because the truck is new to me and i dont know her that well yet . ill get back to you and see if its any better
thanks
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
hey doc i tried the sensor and the wires look good and the sensor was seated good.could the problem be the catalitic converter????
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.