Hey all, I have a 93 jimmy with 4.3l Vortec. Recent updates are complete tune up, new fuel filter, and sending unit, new egr valve...136k....I have been having this problem before and now after these fixes...this is a random problem sometimes it happens once a day other times 2 or 3 times...sometimes it won't happen for a few days or even a couple weeks...
Been told its possible might be a map sensor or tps sensor...absolutely no check engine lights have ever came on...
Problem is truck will be running fine..all of a sudden ill stop at a light or stop sign go to take off and the truck has no power..takes forever to get up to speed and it will not downshift..I can get the truck up to 70 or 75mph and the rpms will just slowly climp and never drop down...running at 65mph on the highway it runs at 3500rpm which is extremely high since when the truck is running fine its under 2000rpm at 65mph
Now heres the weird part, I can come up to a stop sign kill the truck, wait a minute restart it, and the problem disappears? It may do it later on in the day or not again for another day or two. Fuel economy was horrible before the recent updates i was getting 11mpg...Now its around 14mpg but varys all the time some tanks 14mpg some 12mpg...drive it the same every time.

Sorry for the long post but someone please give me some input, should I just buy both sensors and change them? They are not that expensive. Thanks

 

Buying them both is the fix Im shooting for... Ive been having some trouble with mine. Mine likes to stall out when stopping sometimes (2 times a day, or not for a week) and occasionaly will just stumble while at speed with no pedal response. Sometimes I get an EGR code, sometimes I get a TPS code... Most times I get NO code at all just the stall or the stumbles. Im just so mad Im going to buy them both tomorrow and see how that does, too bad the EGR is expensive though, Ill try the TPS first and hope that fixes it. My TPS seems to be quite stiff compared to other ones Ive tinkered with and is covered in some white powder. My EGR seems fine, not plugged, plunger moves easily... Im stumped. If you change them both please let us know how it worked out.

Ive been driving it for a week with my fuel pressure guage sticking up out of the hood so I can monitor it, and its not fuel delivery related...

 

Mine has never stalled or dies at all..it actually runs good besides bad fuel mileage at times, which is what I find weird as well..especially that I turn it off and turn it back on and BAM its fixed initially for a while..planning on buying both tomorrow unless I get some other responses on here..

 

Upon re reading your post, I am wondering if your transmission is having a shifting problem... You shouldnt be able to go 65 at 2000 and 3500 RPM unless its running in OD sometimes, and Drive on others... And the slow getting up to speed sounds like it may be staying in drive when you stop and not shifting down on its own like it should. When you are slowing down can you see your RPM changing as its going down through the gears when stopping? Or hear it shifting properly? How about on accelerating, you should be able to hear if its shifting properly. You may want to climb down underneath and check the condition of the vaccum line going to the shift controller on your transmission... I guess that all depends on which transmission you have too. Cant hurt to take a look though.

 

Upon accelerating it does not shift the rpms just keep climbing slowly and the truck will not downshift to a "cruising" rpm...deceleration it does slow the rpms but again I cannot really feel it shift..I have no idea what trans I have? I never thought this would be a trans problem since it was so random.

 

Yeah there is a little electronic shift solenoid on your transmission thats prolly going on the fritz. Its the thing that the wireplugs go into on the outside of the trans... On www.rockauto.com they are about 40-70 bucks US. Im not a transmission guy by far, but for a cheap price I would try it anyways. Maybe go to the U Pull It yard and just grab one off another truck there. They are the same on any 4L60 transmissions so you can probably take one from a half ton truck too if need be.

SwartKK and Gimpyblazer are the man around here, Im sure they will chime in here tonight sometime with an opinion.

 

Ok which part are you talking about, I went to advanceautoparts.com and these are all the trans solenoids they sell?

http://shop.advanceautoparts.com/web...ssion+Solenoid

 

This morning driving to work as I pulled off my street from a stop sign, truck as it was shifting to 2nd lunged forward hard and made a loud clunk, shifted extremely hard. Then it started performing its usual power loss, no acceleration or downshifting to cruise. I pulled over killed the ignition, started it back up and it has been fine since? Any ideas anyone? I am completely lost here.

 

That link didnt show my any parts.... Im sure the thing is called a 'Shift Solenoid" or pressure control solenoid or something like that. It shouldnt be too expensive. You may want to save yourself the headache and pop into a transmission shop and but what you need from them. I bet you explain your problem to the trans mechanic and they know exactly whats wrong with your ride, and they will have the part you need in stock. May cost a little more than the parts store one since they will want to make a few bucks, but Im certain the problem is on your transmission.