66gtk Posted March 20, 2020 Author Share Posted March 20, 2020 OK folks...I've gotten good help and advice here and I want to revive this discussion. A quick update to where we left off in the fall. Shortly after having the carb rebuilt I had to put it away for the winter. By shortly, I mean less than a week. During that week the truck started acting up pretty much from day one - right after posting the update. I'll explain the issue: Intermittent off-idle and near idle stumbling: - First, the good - starts up easily every time now. Restarts easily - EFI like type easy. Idles fine when cold or hot after starting. Does not stink like a rich fuel issue or blow smoke. Very clean burning system right now. The first few off-idle accelerations from a stop are generally really good after a cold start. Once warmed up, things become inconsistent. Once cruising on highway or at steady load it seems to run fine. Only when transitioning between certain loads does it have the intermittent "falling on it's ass" syndrome - Now, back to the issue... There are 2 general subtypes of the issue, but I think they are both the same, which relate to very poor fuel delivery issues off-idle or near idle. Gas is fresh and new fuel filters are in place in a couple locations and I will continue to monitor and change these as necessary. 1. After stopped at a light or sign with really good idle performance the truck will stumble and stall if I don't modulate the throttle by blipping the accelerator a certain way. It will also completely kill out in the middle of an intersection if I fail to revive it with my right foot. Once it takes off, it will either pull away with good power and load or it will act as if it's not getting any fuel despite the throttle being applied and will not accelerate with any power. If I reset the accelerator pedal I can sometimes get the truck to act much differently within a second. This behavior is highly unpredictable and inconsistent. I would say after driving about 100 miles so far the past 2 weeks it will do this 50 percent of the time. 2. While cruising under load on HWY or on the boulevard if I decelerate by pulling foot from the throttle in a quick manner the engine will struggle and start bucking while nearly dying. It will sometimes die as I roll into the full stop after doing this bucking (you can hear it) but it's not frequent. It can do it while backing off throttle to prepare for an exit ramp. Again, highly inconsistent and this #2 behavior is far more infrequent now than he 1st behavior described. When truck has good constant throttle response and power it feels really good to me and the transmission shifts at proper shift points very well and dare I say even nice and smooth. No slipping. When the throttle response is eratic it seems like the truck fails to respond to throttle well, as if it's in a really high gear, even though it isn't necessarily so. Kind of like when you miss a 2-3 shift in a standard transmission and hit 5th gear instead. That's what the truck feels like - it's bogging bad when it behaves this way. A moment later it's fine, and then it misbehaves again and then it's fine.... it's maddening. These issues are all related to an acceleration or deceleration change demand. My throttle is very stiff, too. We have examined and adjusted the throttle cable as much as we could - no binding. I have ordered a new throttle cable to try but have not installed it yet. You can see in the photos above that it's factory - likely the original. Thanks for following along - I know it's a lot to absorb. My wrencher friend who works on this truck for me thinks it's related to the EEC trying/failing to do it's job but he honestly doesn't know. We did play with adjusting the accelerator pump arm but didn't notice any improvement. We followed the advice learned here and elsewhere to ensure the distributor and rotor are properly phased and we are running the correct goofy rotor and the correct goofy timing order that goes with it in respect to wiring the ignition wires to the distributor. You will notice in the photo I shared earlier it was using the traditional rotor and firing order, which was wrong. Strangely, the truck didn't behave any different either way. Plugs, wires, rotor, cap all brand new. Any suggestions before I pull out all the CA stuff? Please keep in mind I'm not a mechanic so plain English is often required as well as step by step instructions / photos. Thanks so much!! Troy Cold start Drive (short video ends with truck dying in the intersection) Hot idle after drive and restart Another idle video from end of winter storage Link to comment Share on other sites More sharing options...
Gary Lewis Posted March 20, 2020 Share Posted March 20, 2020 Cold start Drive (short video ends with truck dying in the intersection) Hot idle after drive and restart Another idle video from end of winter storage Did it die in the intersection in the second video? On transition from idle? It seemingly runs well save for what appear to be problems on transitions. So I'm hoping you can get that sorted and not have to pull all the other stuff off. But, if you do, here are some thoughts: The EEC systems I've been around on these trucks were stand-alone systems, meaning they had their own wiring. The ECA/ECU on my '82 was under the driver's seat and there was a boot that went into the floor to seal the wire. I wound up cutting the harness not far off the ECA, traced those wires to each of the senders/actuators, and then removed each of those awa the associated wiring. It wasn't too bad since it was an add-on harness so wasn't integrated into the other wiring. Sometimes it went under another harness, but I could usually slide it out and continue following it to the sender or actuator. You'll have a large tote full of "stuff" if you do that. And you'll have to replace the distributor and ignition module as well as the wiring to it. Plus, the carb is a feedback unit, and there won't be any input to it. You could try to run it and see how it does. It may work just fine, or it may not. But you said you have the dizzy, ignition module, wiring, and carb, so you are basically set. Link to comment Share on other sites More sharing options...
66gtk Posted March 20, 2020 Author Share Posted March 20, 2020 Did it die in the intersection in the second video? On transition from idle? It seemingly runs well save for what appear to be problems on transitions. So I'm hoping you can get that sorted and not have to pull all the other stuff off. But, if you do, here are some thoughts: The EEC systems I've been around on these trucks were stand-alone systems, meaning they had their own wiring. The ECA/ECU on my '82 was under the driver's seat and there was a boot that went into the floor to seal the wire. I wound up cutting the harness not far off the ECA, traced those wires to each of the senders/actuators, and then removed each of those awa the associated wiring. It wasn't too bad since it was an add-on harness so wasn't integrated into the other wiring. Sometimes it went under another harness, but I could usually slide it out and continue following it to the sender or actuator. You'll have a large tote full of "stuff" if you do that. And you'll have to replace the distributor and ignition module as well as the wiring to it. Plus, the carb is a feedback unit, and there won't be any input to it. You could try to run it and see how it does. It may work just fine, or it may not. But you said you have the dizzy, ignition module, wiring, and carb, so you are basically set. Gary - Yes, in that video it was running/idling well until taking off from that stop where it died in the intersection. Link to comment Share on other sites More sharing options...
Gary Lewis Posted March 20, 2020 Share Posted March 20, 2020 Gary - Yes, in that video it was running/idling well until taking off from that stop where it died in the intersection. If it was me I'd pull the connector to the throttle position sensor, but a DVM on it, and watch to see what happens as you slowly open and close the throttle. (Actually what would be better would be an analog ohm meter so you could see the meter move.) Link to comment Share on other sites More sharing options...
66gtk Posted March 20, 2020 Author Share Posted March 20, 2020 If it was me I'd pull the connector to the throttle position sensor, but a DVM on it, and watch to see what happens as you slowly open and close the throttle. (Actually what would be better would be an analog ohm meter so you could see the meter move.) Gary - where exactly is the TPS?? Link to comment Share on other sites More sharing options...
66gtk Posted March 20, 2020 Author Share Posted March 20, 2020 Gary - where exactly is the TPS?? This? Link to comment Share on other sites More sharing options...
Gary Lewis Posted March 20, 2020 Share Posted March 20, 2020 Gary - where exactly is the TPS?? On the front passenger's side corner of the carb according to the illustration I have. And it has three wires to it, which you can see in the schematic below - and while it isn't completely accurate for your truck, the TPS circuit is correct: Orange/White: VREF, which is Circuit 351 Dark Green/Light Green: Circuit 355 Black/White: SRTN which is Circuit 359 As for testing it, go to Documentation/Electrical/ELECTRONIC ENGINE CONTROL (EEC) and go to the EEC-III tab. Then scroll down to Page 28-64, where the testing is explained. But note that they mention the name of the signal going to the TPS, and not the color of the wire. However, they also show the circuit #, which is why I did the translation above. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted March 20, 2020 Share Posted March 20, 2020 On the front passenger's side corner of the carb according to the illustration I have. And it has three wires to it, which you can see in the schematic below - and while it isn't completely accurate for your truck, the TPS circuit is correct: Orange/White: VREF, which is Circuit 351 Dark Green/Light Green: Circuit 355 Black/White: SRTN which is Circuit 359 As for testing it, go to Documentation/Electrical/ELECTRONIC ENGINE CONTROL (EEC) and go to the EEC-III tab. Then scroll down to Page 28-64, where the testing is explained. But note that they mention the name of the signal going to the TPS, and not the color of the wire. However, they also show the circuit #, which is why I did the translation above. I need to steal this illustration, showing C109 for the other thread looking at the spout on a 1985 4.9. I'm not that nimble on a phone, pasting images into replies. Link to comment Share on other sites More sharing options...
Gary Lewis Posted March 20, 2020 Share Posted March 20, 2020 I need to steal this illustration, showing C109 for the other thread looking at the spout on a 1985 4.9. I'm not that nimble on a phone, pasting images into replies. You did it! Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted March 20, 2020 Share Posted March 20, 2020 You did it! With your help. Thanks Gary! Link to comment Share on other sites More sharing options...
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