Hello guys, im new here, ive got a 1998 gmc sierra k1500 4.3L v6, its got the vortec motor and 183 thousand on it, auto trans, fresh oil change, new fuel filter, rran the seafoam thru brake booster line, new spark plugs, my biggest problem is, when im doing 50-55 mph on flat ground it goes like a champ... but when you try to go uphill (like a 8-10% grade) it will stay in 4th gear and slow WAY down... in other words not downshift when it needs to.. the other day i pulled the throttle body off to clean it and the 2 sensors (IAC and TPS) and its was BLACK under there... so i cleaned it with carb clean and a new toothe bruch on my work bench... i also cleaned the IAC, the only cable that was hooked up to the throttle body was the throttle cable.. but theres a little black nub where i believe the "detent" or "kickdown" cable goes... my plate that holds the throttle cable before the t-body has an empty square hole next to throttle cable.. am i missing the detent cable?? not sure what trans is in it other than its stock and its an auto... or does this even have a detent cable? it starts right up and runs great... just doesnt downshift when needs to.. unless i floor it for a few mins... but there goes my gas. lol, if anyone can help me that would be great...
98 gmc sierra k1500 wont downshift in time...
- Thread starter Clyde51
- Start date
98trck
Member
when was the last time the trans was serviced?
Not sure, honestly dont think it ever was.... the guy i bought it off (original owner) was far from mechanicly inclined.... as fas as serviced you mean new fluids and filter? cuz i know how to do that... i do it to every truck but havent to this one YET, my fluid looks good and doesnt smeel burnt... and theres NO leaks on the truck... (for once in my life). ive been thinking of doing a transmission cooler flush, where you unhook the supply line and drain it into a bucket while truck is running and keep feeding new fluid that way it runs all old junk out... any thoughts on that? and what about sea foam trans tune??? im VERY suspisous of that stuff although i use it in my top end (thru brake booster) and have never had a problem... please let me know what you guys think, possibly a plugged filter? and how do i get ALL old sh*t out?
So i changed fluids and filter, i was wicked low and really black... and magnet had alot of sludge on it but no metal filings... so i put a new filter in and fluid, seems to be a little better but not much of a difference... still slagging on the hills... i noticed it started shaking a little when i goosed it to try to get it to down shift... but once it shifted down it cleared back up
so if anyone can let me know if theres supposed to be a detent cable or not please let me know, and also, i noticed when i turn the key after its been sitting for a few hours and just go to start it... it will just crank for a few seconds then hesitate and finally i turn key off, restart and it actually starts.... I personally think i need a new fuel pump.... but cant afford that.. i noticed when i took my fuel filter out, i had ran the truck abut an hour before pulling filter out, and i watched a video of a guy changing his fuel filter and gas SPRAYED out.... mine just trickled out... almost as if there was no pressure... and where is the pressure regulator? can someone please tell me where that is and how can i do a pressure test? i cant find the valve people talk about... just a little green cap on the gas line going to engine that says "evap service port, 1 psi....something". ive got upcoming work to do with "big dirty" so if anyone can help that would be great. also please dont forget to include fuel pressure specs (how much is good psi and how much is not) thanks!
so if anyone can let me know if theres supposed to be a detent cable or not please let me know, and also, i noticed when i turn the key after its been sitting for a few hours and just go to start it... it will just crank for a few seconds then hesitate and finally i turn key off, restart and it actually starts.... I personally think i need a new fuel pump.... but cant afford that.. i noticed when i took my fuel filter out, i had ran the truck abut an hour before pulling filter out, and i watched a video of a guy changing his fuel filter and gas SPRAYED out.... mine just trickled out... almost as if there was no pressure... and where is the pressure regulator? can someone please tell me where that is and how can i do a pressure test? i cant find the valve people talk about... just a little green cap on the gas line going to engine that says "evap service port, 1 psi....something". ive got upcoming work to do with "big dirty" so if anyone can help that would be great. also please dont forget to include fuel pressure specs (how much is good psi and how much is not) thanks!
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update: i just bought a pressure tester, its 63 PSI key on (acc position) then aftyer pump shuts off its 60 psi, 55 psi with truck idling... what gives? am i missing something or just expecting more out of a v6 than it has?