JMUBullnose Posted April 20, 2018 Share Posted April 20, 2018 Hello folks - me again... Just remembered this after driving in Old Red today. (FYI - think I'm happy with the shifting, now think I have a misfire situation!) However, when I was last under the hood I noticed a random disconnected pigtail on the drivers side firewall, directly behind the valve covers. Anyone know what this should have connected to? Link to comment Share on other sites More sharing options...
Gary Lewis Posted April 20, 2018 Share Posted April 20, 2018 Glad you are making progress. These trucks are like onions - we keep peeling the layers and crying, but it is all good if you like onion rings. As for the pigtail, it doesn't look like a Ford connector. But, there should be a ground from the engine, usually from the valve cover bolt to the wiper motor. Do you have that ground? Link to comment Share on other sites More sharing options...
JMUBullnose Posted April 20, 2018 Author Share Posted April 20, 2018 Glad you are making progress. These trucks are like onions - we keep peeling the layers and crying, but it is all good if you like onion rings. As for the pigtail, it doesn't look like a Ford connector. But, there should be a ground from the engine, usually from the valve cover bolt to the wiper motor. Do you have that ground? Hmm, I'll have to look when I go back out there at lunch time. I guess I'll be replacing plugs and wires this weekend (have had them sitting on the shelf for a bit!). Hopefully that helps with the misfire...it definitely presents itself once the engine is warmed up. Link to comment Share on other sites More sharing options...
Rembrant Posted April 20, 2018 Share Posted April 20, 2018 However, when I was last under the hood I noticed a random disconnected pigtail on the drivers side firewall, directly behind the valve covers. Anyone know what this should have connected to? That very same plug is hanging on the firewall of my 1984, also not connected to anything. It never was on my truck. Ford just used a generic ground cable I'd guess, and it was unused on some models. Maybe it was used on the trucks with the EEC-IV or whatever it is called? Gary, it is part of the engine ground cable. The unused pigtail is crimped in the firewall end connector of the engine ground cable. The engine end of the cable I believe goes under one of the screws that attach the throttle bracket to the intake manifold. Link to comment Share on other sites More sharing options...
JMUBullnose Posted April 20, 2018 Author Share Posted April 20, 2018 That very same plug is hanging on the firewall of my 1984, also not connected to anything. It never was on my truck. Ford just used a generic ground cable I'd guess, and it was unused on some models. Maybe it was used on the trucks with the EEC-IV or whatever it is called? Funny enough I was just wondering about the whole EEC-IV thing - what's the differences? I was looking at new distributor caps and rotors while puzzling the misfire issue and saw some of the kits called out specifically EEC & non-EEC and I have no clue which I have. Link to comment Share on other sites More sharing options...
Rembrant Posted April 20, 2018 Share Posted April 20, 2018 Funny enough I was just wondering about the whole EEC-IV thing - what's the differences? I was looking at new distributor caps and rotors while puzzling the misfire issue and saw some of the kits called out specifically EEC & non-EEC and I have no clue which I have. I believe the quickest visual clue is whether you have vacuum advance on your distributor or not. If you have a vacuum advance line, then your truck is Duraspark II, not EEC-IV. No vacuum advance, then you have an electronic distributor and feedback carb (EEC-IV). The second bit of evidence, as shown in your picture, is that big black rubber plug in the firewall right next to where the unused pigtail is. If your truck was EEC-IV, then there would be a bundle of wires going through the firewall where that plug is, to the ECU in the cab. Somebody can correct me if I'm wrong here, but that is my understanding of the quick and dirty checks as to EEC-IV and non EEC-IV. I think there is a a bit of a misconception that all 1984 trucks were EEC-IV. Maybe it was a mid-year change, I dunno, but my 1984 is not EEC-IV, and it doesn't look like yours is either. I've found others in my searches as well. My truck was a one owner unmodified vehicle, so it came from Ford that way. As always, take it all with a grain of salt. I'm certainly no expert, but I did go through all this originally when ordering parts for my '84 F150. Link to comment Share on other sites More sharing options...
Gary Lewis Posted April 20, 2018 Share Posted April 20, 2018 Funny enough I was just wondering about the whole EEC-IV thing - what's the differences? I was looking at new distributor caps and rotors while puzzling the misfire issue and saw some of the kits called out specifically EEC & non-EEC and I have no clue which I have. I believe the quickest visual clue is whether you have vacuum advance on your distributor or not. If you have a vacuum advance line, then your truck is Duraspark II, not EEC-IV. No vacuum advance, then you have an electronic distributor and feedback carb (EEC-IV). The second bit of evidence, as shown in your picture, is that big black rubber plug in the firewall right next to where the unused pigtail is. If your truck was EEC-IV, then there would be a bundle of wires going through the firewall where that plug is, to the ECU in the cab. Somebody can correct me if I'm wrong here, but that is my understanding of the quick and dirty checks as to EEC-IV and non EEC-IV. I think there is a a bit of a misconception that all 1984 trucks were EEC-IV. Maybe it was a mid-year change, I dunno, but my 1984 is not EEC-IV, and it doesn't look like yours is either. I've found others in my searches as well. My truck was a one owner unmodified vehicle, so it came from Ford that way. As always, take it all with a grain of salt. I'm certainly no expert, but I did go through all this originally when ordering parts for my '84 F150. I think you are right on that. Good points. As for the ground, I'm glad to know that. Thanks! Link to comment Share on other sites More sharing options...
NotEnoughTrucks Posted April 21, 2018 Share Posted April 21, 2018 That very same plug is hanging on the firewall of my 1984, also not connected to anything. It never was on my truck. Ford just used a generic ground cable I'd guess, and it was unused on some models. Maybe it was used on the trucks with the EEC-IV or whatever it is called? Funny enough I was just wondering about the whole EEC-IV thing - what's the differences? I was looking at new distributor caps and rotors while puzzling the misfire issue and saw some of the kits called out specifically EEC & non-EEC and I have no clue which I have. Well, unless you have that feedback carburetor thingy, you won't have EECIV in your 84 F150. I think that pigtail may be the power for the underhood light. Link to comment Share on other sites More sharing options...
ctubutis Posted April 21, 2018 Share Posted April 21, 2018 Well, unless you have that feedback carburetor thingy, you won't have EECIV in your 84 F150. ^True I think that pigtail may be the power for the underhood light. Bingo! Light green/yellow-stripe, 15A fused, always-on power for optional underhood lamp. Link to comment Share on other sites More sharing options...
Rembrant Posted April 21, 2018 Share Posted April 21, 2018 I think that pigtail may be the power for the underhood light. It's an unused ground. Here's a little clearer view of it on my truck. Easier to see with no engine;). It is crimped in the firewall end of the engine ground cable. Link to comment Share on other sites More sharing options...
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