ratdude747 Posted September 5, 2019 Author Share Posted September 5, 2019 Before replacing the TPS [probably needed, as Gary suggested], try to set the idle [warm engine with fully opened choke] to a slow steady speed [~650 RPMs]. Attach a rubber vacuum hose to an unused port [manifold vacuum] and with a vacuum gauge, adjust timing [spout disconnected] for the highest vacuum reading. This should approach 20" of Hg. You can use the same method for adjusting the idle air/fuel mixture. If the idle speed gets too high, lower with the idle speed screw and check everything again until you get a steady idle. Reconnect the spout wire and see if the engine runs better. Noted. I will note that my idle got a lot worse when timing was adjusted (SPOUT disconnected). Maybe it was actually correct to begin with? Link to comment Share on other sites More sharing options...
85lebaront2 Posted September 5, 2019 Share Posted September 5, 2019 Noted. I will note that my idle got a lot worse when timing was adjusted (SPOUT disconnected). Maybe it was actually correct to begin with? Disconnecting the SPOUT simply locks the timing at the static setting, if you look at it once you plug the SPOUT back in, you will see the timing jumps sharply to the advance side (mine at 10° BTDC SPOUT unplugged, will go to 20 - 25° BTDC when reconnected. As a result, the engine slows down and in your case since it is carbureted the mixture gets a little off. One important item to look at on the carburetor, with the air cleaner off, grab the top of the carburetor and try to move it, it should be solid, if it moves, look a the throttle body the float bowl area, if the bowl is moving on the throttle body, it will (a) destroy the gasket (b) cause mixture issues and © give accelerator pump problems. Link to comment Share on other sites More sharing options...
Gary Lewis Posted September 5, 2019 Share Posted September 5, 2019 Noted. I will note that my idle got a lot worse when timing was adjusted (SPOUT disconnected). Maybe it was actually correct to begin with? It is possible that the damper has slipped, making the timing mark off. I’ve seen that happen many times. In fact, my “new” damper on Big Blue is off by about 4 degrees. Stick a piston stop in the #1 spark plug hole to find out. Link to comment Share on other sites More sharing options...
ratdude747 Posted September 5, 2019 Author Share Posted September 5, 2019 It is possible that the damper has slipped, making the timing mark off. I’ve seen that happen many times. In fact, my “new” damper on Big Blue is off by about 4 degrees. Stick a piston stop in the #1 spark plug hole to find out. Just for the heck of it, I "by ear" advanced my ignition timing back to approximately where it was when I bought it (have a timing light in the truck, but I didn't record where it was shown as). From the limited testing I could do over lunch break, it seems to run a bit better (no time to hit the highway, but far less lugging at 25mph). The idle is rough... but that could be a idle mix issue relating to the timing change (too rich?). I'll determine #1 TDC and verify after work. ------- The carb is solid. Already checked. No loose screws or leaks that I can find. I do know that when spout is connected, the timing should shift to around 20 degrees (which is what I observed). My assumption was that without the extra advance it was supposed to "not" idle well, hence why I didn't doubt my timing adjustment initially. Link to comment Share on other sites More sharing options...
reamer Posted September 5, 2019 Share Posted September 5, 2019 Just for the heck of it, I "by ear" advanced my ignition timing back to approximately where it was when I bought it (have a timing light in the truck, but I didn't record where it was shown as). From the limited testing I could do over lunch break, it seems to run a bit better (no time to hit the highway, but far less lugging at 25mph). The idle is rough... but that could be a idle mix issue relating to the timing change (too rich?). I'll determine #1 TDC and verify after work. ------- The carb is solid. Already checked. No loose screws or leaks that I can find. I do know that when spout is connected, the timing should shift to around 20 degrees (which is what I observed). My assumption was that without the extra advance it was supposed to "not" idle well, hence why I didn't doubt my timing adjustment initially. Just found my loss of power at highway speeds as a plugged cat converter... Link to comment Share on other sites More sharing options...
ratdude747 Posted September 5, 2019 Author Share Posted September 5, 2019 Just found my loss of power at highway speeds as a plugged cat converter... Already did a backpressure test, less than 1PSI. Link to comment Share on other sites More sharing options...
ratdude747 Posted September 6, 2019 Author Share Posted September 6, 2019 Already did a backpressure test, less than 1PSI. Yesterday I tried playing with the timing to get the intermittent rough idle (pinging?) out... which brought me to 10 degrees advanced from the 10 degree mark I originally timed to. No change to the idle fuel screw helped. At idle (A/C) off I'm get right at 20 in of vacuum. Still lugs at 25mph... maybe this is a condition the AOD doesn't handle well and in such case, I just need to push until it downshifts? At 35mph or so it downshifts almost instantly when I give it a bit of gas. Or do I possibly have a valve body issue? Haven't had time to test it on a long enough stretch of highway to test speeds over 55. I might poke around on ebay and see if I can find a deal on a TPS... Edit- found a BWD one for $13 shipped... you gotta love liquidation sellers Link to comment Share on other sites More sharing options...
85lebaront2 Posted September 6, 2019 Share Posted September 6, 2019 Yesterday I tried playing with the timing to get the intermittent rough idle (pinging?) out... which brought me to 10 degrees advanced from the 10 degree mark I originally timed to. No change to the idle fuel screw helped. At idle (A/C) off I'm get right at 20 in of vacuum. Still lugs at 25mph... maybe this is a condition the AOD doesn't handle well and in such case, I just need to push until it downshifts? At 35mph or so it downshifts almost instantly when I give it a bit of gas. Or do I possibly have a valve body issue? Haven't had time to test it on a long enough stretch of highway to test speeds over 55. I might poke around on ebay and see if I can find a deal on a TPS... Edit- found a BWD one for $13 shipped... you gotta love liquidation sellers Ok, AOD transmission is a straight through mechanical connection in drive (3rd gear) If it feels like it is lugging, it may well be. From what I remember on my son's 1986 F150 with a 302, it wasn't super happy at 25 in 3rd. Are the transmission shifts very hard (firm) or just a nice solid shift at part throttle? Are they maybe a bit soft, feel like they are slipping particularly into 3 or 4? These transmissions are super sensitive to throttle cable adjustments, not the one to the carburetor, but the one to the transmission. I know these were only used briefly on the six due to it's torque, the later trucks actually got the E4OD on everything except the 302. Some 302s had E4ODs, notably 4WD models. Link to comment Share on other sites More sharing options...
ratdude747 Posted September 8, 2019 Author Share Posted September 8, 2019 Ok, AOD transmission is a straight through mechanical connection in drive (3rd gear) If it feels like it is lugging, it may well be. From what I remember on my son's 1986 F150 with a 302, it wasn't super happy at 25 in 3rd. Are the transmission shifts very hard (firm) or just a nice solid shift at part throttle? Are they maybe a bit soft, feel like they are slipping particularly into 3 or 4? These transmissions are super sensitive to throttle cable adjustments, not the one to the carburetor, but the one to the transmission. I know these were only used briefly on the six due to it's torque, the later trucks actually got the E4OD on everything except the 302. Some 302s had E4ODs, notably 4WD models. The shifting isn't particularly harsh, but not particularly soft either. Maybe I need to go tighter on the TV cable? I tried to get to the idle port to plug in a pressure gauge (Harbor Freight Oil Pressure set) but the cat was in the way and I got tired of fighting with it. Hence why I deferred to the "zero slack" adjustment method. ---- Drove it a bunch this evening, nope, still lugging. It did OK at 65mph sometimes... but other times, as soon as OD kicked in, the speedo dropped like a rock. Likely unrelated issue: The ignition switch took a shit and nearly stranded me. I knew the accesory position was toast (only works in one exact spot, not the entirety of the detent)... but with key on, backing out of my parents driveway, it jumped to half-start (brake light came on, accessories dropped out), then died. Took a few swipes to get run back... and then I smelled burning electrical stuff. Parked for 5 minutes, tried again, no problems. Was able to get it to act up once I got home... so the contacts are probably toast in there. Toast enough to voltage drop the electrical system into not giving good spark? I doubt it, but at this point anything is fair game. Still waiting on the TPS to come in. Looks like I'm driving the Ranger tomorrow. Why I have two trucks. Link to comment Share on other sites More sharing options...
ratdude747 Posted September 16, 2019 Author Share Posted September 16, 2019 The shifting isn't particularly harsh, but not particularly soft either. Maybe I need to go tighter on the TV cable? I tried to get to the idle port to plug in a pressure gauge (Harbor Freight Oil Pressure set) but the cat was in the way and I got tired of fighting with it. Hence why I deferred to the "zero slack" adjustment method. ---- Drove it a bunch this evening, nope, still lugging. It did OK at 65mph sometimes... but other times, as soon as OD kicked in, the speedo dropped like a rock. Likely unrelated issue: The ignition switch took a shit and nearly stranded me. I knew the accesory position was toast (only works in one exact spot, not the entirety of the detent)... but with key on, backing out of my parents driveway, it jumped to half-start (brake light came on, accessories dropped out), then died. Took a few swipes to get run back... and then I smelled burning electrical stuff. Parked for 5 minutes, tried again, no problems. Was able to get it to act up once I got home... so the contacts are probably toast in there. Toast enough to voltage drop the electrical system into not giving good spark? I doubt it, but at this point anything is fair game. Still waiting on the TPS to come in. Looks like I'm driving the Ranger tomorrow. Why I have two trucks. Some quick updates: -I replaced the TPS... idle got worse. Still lugging. But it did make a difference. I reset the base timing to 10 degrees (as per the indicator) and readjusted the idle fuel with no change either way. -Yesterday, I power cycled the ECU... and things got way, way worse. Stalled on me several times... and lugged a lot worse than before. I didn't have time to readjust the idle fuel (had to go to Church). Something is very wrong here. Right now she's out of commission due to a brake line blowing up on my way home. I've pulled the line (rubbed on a frame rivet on one spot, and locally rusted out) and will be bending/flaring it this evening after work. That said, it seems that something is off. Either I'm not getting good fuel delivery (which makes no sense; no vacuum leaks, rebuilt carb, and adequate fuel supply), or I wonder if I have a mechanical problem (low compression, bad valve timing/adjustment, etc.). My next move will probably be to obtain a compression tester and see what I'm getting there. Thoughts? Link to comment Share on other sites More sharing options...
Recommended Posts