DerekTheGreat
Forum Regular
Hey everyone, hope things are going swell. I'm Derek and am excited to be on this forum. Hopefully you guys can assist with a few lingering issues we have with our truck and hopefully I can one day help others too. Now for the backstory...
I've been meaning to join this site for some time as it has helped me and my GF a lot with her truck. Last year she bought a 1988 GMC C3500 SLE regular cab long box. It's got the SM465 trans and 454 TBI engine. 70k miles but it lived it's life outside. No rust other than one pebble sized spot on the passenger cab corner. Just had to have it, haven't seen another GMT400 one-ton truck that wasn't a automatic, 4x4 crew/extended cab, dualie or some combination of those, not to mention with all the options this one has. It pretty much looks like a typical long box 1500 but it all ends there.
When we bought it, it didn't want to idle, animals chewed most of the wires for the running lights and some were repaired by the PO to get it running again. Guy was a (gasp) mechanic and I went against my better judgement buying it from him.. Gas pedal was stiff, speedo didn't work, neither did the cruise, A/C, horns, wipers and the brake light didn't illuminate when the key was flipped to run position, plus someone had swapped a Dodge bumper on the back- I didn't realize that until later.
It overheated and belched black coolant everywhere on the ride home from grand rapids. Made the GF really happy LoL. I told her our new vehicle is bonding with us and what a way to start.
We've since rebuilt the throttle body, resprayed the top half, flushed all the fluids, put a new A/C Delco distributor on it, wires & plugs as specified by the service manual. I did the moonies to needles swap and got the speedo to work again, replaced the throttle cable, repaired all the wires, put a correct bumper on it, replaced the headliner, swapped on the chrome swing mirrors in place of the tripost trailering ones, replaced all the lights, put a new radiator on it, new thermostat, new upper & lower radiator hose, new horns (well JY ones that worked), replaced the axle seals, wiper motor, washer bottle & pump, repaired lots of other wiring blah blah.
Fix list:
-Cured the "not want to idle when started" thing by adjusting the base idle (guy had already punched out the cap)
-Brake light didn't come on because the guy cut the wire.. So fixed the wire, found out why he cut it because it stayed on. Replaced rear ABS module and it went away.
-Fixed the speedo by replacing a bad fuse terminal, gages fuse IIRC was corroded and not sending power to the speedo.
-Theres more, just figure you guys don't want to read all that BS...
One problem that still persists is that the thing still idles high in my opinion. Tach says 1000 but scanner says 800. If you unplug the IAC it goes down to where I set the base idle, 450 or so. Plug it back in and it will eventually creep up to 800. I'd like it to idle at 650 but what should these F'n things idle at??? No where can I find the actual spec on the idle speed, nothing at all. If anything it's a matter of opinion...
Another problem is that the truck will "hold" a high rpm when trying to change gears. I'll take 1st to 15 or so, truck reads say 2100rpm, push clutch in go to 2nd and I'll have to hold the clutch down for 20 seconds before the POS will abruptly go back down enough for me to take my foot off the clutch. Does this on all gear changes, sometimes worse than others and very very very rarely it won't do it at all. I've swapped the fuel pressure regulator, injectors (from a JY TB, it actually ran better!) IAC valve with a new one from A/C Delco. Also, unlike my '89 TBI Fireturd it doesn't go to a high RPM when started cold, sometimes it goes to ~1,200 but the Fireturd goes to ~1,600 and then slowly goes down to ~650 as it warms up. Not sure what the trucks are supposed to do.
Another problems is it surges when accelerating. I'll be holding my foot steady on the go pedal and it will feel like someone is bumping into me slightly. It does this most right around when it is getting ready to go into closed loop. (PO replaced temp sender & I verified that it works like it should). Once in closed loop it doesn't do that so much but it also feels like it's got no power either. When cold it's got gobs but hot it's a bit of a turd. I know people say to run 8 degrees base timing but our truck hated it, I compromised at 6..
What do you guys think?
I've been meaning to join this site for some time as it has helped me and my GF a lot with her truck. Last year she bought a 1988 GMC C3500 SLE regular cab long box. It's got the SM465 trans and 454 TBI engine. 70k miles but it lived it's life outside. No rust other than one pebble sized spot on the passenger cab corner. Just had to have it, haven't seen another GMT400 one-ton truck that wasn't a automatic, 4x4 crew/extended cab, dualie or some combination of those, not to mention with all the options this one has. It pretty much looks like a typical long box 1500 but it all ends there.
When we bought it, it didn't want to idle, animals chewed most of the wires for the running lights and some were repaired by the PO to get it running again. Guy was a (gasp) mechanic and I went against my better judgement buying it from him.. Gas pedal was stiff, speedo didn't work, neither did the cruise, A/C, horns, wipers and the brake light didn't illuminate when the key was flipped to run position, plus someone had swapped a Dodge bumper on the back- I didn't realize that until later.
It overheated and belched black coolant everywhere on the ride home from grand rapids. Made the GF really happy LoL. I told her our new vehicle is bonding with us and what a way to start.
We've since rebuilt the throttle body, resprayed the top half, flushed all the fluids, put a new A/C Delco distributor on it, wires & plugs as specified by the service manual. I did the moonies to needles swap and got the speedo to work again, replaced the throttle cable, repaired all the wires, put a correct bumper on it, replaced the headliner, swapped on the chrome swing mirrors in place of the tripost trailering ones, replaced all the lights, put a new radiator on it, new thermostat, new upper & lower radiator hose, new horns (well JY ones that worked), replaced the axle seals, wiper motor, washer bottle & pump, repaired lots of other wiring blah blah.
Fix list:
-Cured the "not want to idle when started" thing by adjusting the base idle (guy had already punched out the cap)
-Brake light didn't come on because the guy cut the wire.. So fixed the wire, found out why he cut it because it stayed on. Replaced rear ABS module and it went away.
-Fixed the speedo by replacing a bad fuse terminal, gages fuse IIRC was corroded and not sending power to the speedo.
-Theres more, just figure you guys don't want to read all that BS...
One problem that still persists is that the thing still idles high in my opinion. Tach says 1000 but scanner says 800. If you unplug the IAC it goes down to where I set the base idle, 450 or so. Plug it back in and it will eventually creep up to 800. I'd like it to idle at 650 but what should these F'n things idle at??? No where can I find the actual spec on the idle speed, nothing at all. If anything it's a matter of opinion...
Another problem is that the truck will "hold" a high rpm when trying to change gears. I'll take 1st to 15 or so, truck reads say 2100rpm, push clutch in go to 2nd and I'll have to hold the clutch down for 20 seconds before the POS will abruptly go back down enough for me to take my foot off the clutch. Does this on all gear changes, sometimes worse than others and very very very rarely it won't do it at all. I've swapped the fuel pressure regulator, injectors (from a JY TB, it actually ran better!) IAC valve with a new one from A/C Delco. Also, unlike my '89 TBI Fireturd it doesn't go to a high RPM when started cold, sometimes it goes to ~1,200 but the Fireturd goes to ~1,600 and then slowly goes down to ~650 as it warms up. Not sure what the trucks are supposed to do.
Another problems is it surges when accelerating. I'll be holding my foot steady on the go pedal and it will feel like someone is bumping into me slightly. It does this most right around when it is getting ready to go into closed loop. (PO replaced temp sender & I verified that it works like it should). Once in closed loop it doesn't do that so much but it also feels like it's got no power either. When cold it's got gobs but hot it's a bit of a turd. I know people say to run 8 degrees base timing but our truck hated it, I compromised at 6..
What do you guys think?
