Hello, this is my 1985 F150 SWB flareside 4WD with a 300-6 and NP435 four-speed.




The truck still has the feedback carburetor and the TFI ignition. When driving the truck it has what seems like a miss that jerks the entire truck. It used to only happen when in fourth going down the highway at 65 MPH. It was very random and intermittent. It has progressed to doing it in second and third while accelerating in addition to constantly doing it in fourth…mostly. I say mostly because while it will happen most of the time, it doesn’t always happen. Here is a video of what it is doing. In the video I am in third gear and then shift into fourth.


As you can hear, it seems to be cutting out or missing. When it happens, the truck jerks. That is why the camera doesn’t stay fixed on the tachometer. In the video when you hear “seriously,” that is my brother commenting on how it usually does it but it didn’t at that time in third gear. Just so you know it is not sending the truck into limp home mode. The timing is advancing beyond the 10 degrees initial. When it is not doing this, it runs great.

I rebuilt what I believe to be the original carb (still has the metal tag) and the truck ran better than ever. That is, when it wasn’t doing its jerky miss thing. Before and after the carb work, it still did it. I hooked up the vacuum gauge to set the mixture and the best I could get was 17 in/Hg. Rock steady, but kind of low I think. I tried to set the ISC but the Allen head screw stripped out. I then disconnected the battery to clear the codes and drove the truck. It still had that jerky miss.

I had a bunch of vacuum leaks before that caused similar symptoms, so I decided to again check for them. I used a homemade smoke machine using a 2 liter bottle, a cigarette, and an air compressor. I had smoke come out of the bottom of the carb. I replaced the carb base gasket and put RTV (I swear only as a temporary thing) where the throttle shaft sticks out of carb base. That fixed the vacuum leak. There were no other leaks that I could find. It still had that jerky miss.

I then looked on the Internet for some tips. I didn’t think it was fuel related because the fuel filter was full of fuel and I knew there were no vacuum leaks. I figured it had to be ignition related. So in searching, it seems like a lot of people blame the TFI module. I took the module to O’Reilly’s and asked them to test the module like 3 times. The kid working there was a Ford guy and knew about TFI modules. He tested it 10 times and it never failed. He said he had had modules test fine on the machine and were still bad. He told us if we bought a module and it didn’t fix it we could return it. So we bought it and tried it out. It still had that jerky miss.

We took the module back and they gave us a refund. I still kind of thought it was ignition related. I ohmed out the ignition coil and it tested fine. I then wondered if it could be the pickup coil. In trying to find a test for it, I couldn’t find one. A new pickup coil is $20 and a remanufactured distributor is $60. I don’t like to replace parts unless I know they are bad, since I wasted a lot of money when I was younger and didn’t know what I was doing. Is it possible it is the pickup coil and does anyone know how to test it?

I then checked for codes using this website EEC IV Self Test ? Ford Fuel Injection and EEC IV Electronic Engine Control ? EEC 4 OBD Trouble Codes ?. The KOEO codes I got were 11 and then CM I got 18 and 51. 11 means the system is OK. 18 means Ignition TACH signal erratic and 51 means ECT sensor signal is/was too high. The KOER codes I got were 12, 13, 22, and 41. 12 means ISC not controlling idle properly (generally idle too low) and 13 means ISC not controlling idle properly (generally idle too high). 22 means BARO signal out of range and 41 means system lean. The place I got the code definitions was EEC IV 2 digit codes.

The codes 18 and 51 seemed to be linked together in what I’ve read. I don’t have a FSM for the truck, though I need one. Without the FSM, I’m not sure how to test the ECT. The codes 12 and 13 stem from the fact I didn’t adjust the ISC. I’ll have to contort myself with a ½ inch wrench and try to adjust it. The code 22 for the Barometric sensor is again one I’d like to test, but not sure how to without a FSM. The hose is connected to it and the electrical plug is tight. The code 41 being lean could be a lot of things. I’ve read where you are supposed to fix the lower number codes first and see if the higher number codes disappear or stay, then go from there.

Honestly, I am at my wits end. I have been battling this thing for a quite a few months. I realize if I am going to keep the computer, I need a FSM. I have been tempted to DSII swap it, but I have reservations. It runs really well when there are no problems and I have read the feedback carbs give the best mileage. Swapping to DSII would require a carb, distributor, ignition box, wiring harness, ignition coil, and a way to control the EGR without the computer. All that is achievable, but it can get pricey. If I just need one part to fix what I have then I will come out money ahead—on multiple fronts. I am thinking it is the pickup coil in the distributor, but I am not sure. Without having a FSM, is there a test anyone knows about I could do to check it?

Sorry for the novel, I just want to let you know what all I have done. I realize Internet diagnosing is hard. That is why I went into a lot of detail and made the video to help though it is not the greatest quality. I thank you for reading this and any help and guidance is greatly appreciated.

 

I think code 18 is your culprit. That's the signal going to the tach from the ignition, and it is erratic. One guess is the coil, although it could be coil or plug wires or even plugs.

On the coil, just because it measures correctly doesn't mean it is good. As they get hot they sometimes open up and then close again. But, they usually just quit and don't hiccup.

On to the wires/plugs. What you've described fits with a bad wire or plug. What usually happens is that the spark jumps to something else as the cylinder pressure goes up and makes it hard to jump across the gap. And cylinder pressure goes up as the load on the engine goes up. So, the load is high in top gear, but less at the same speed if you shift down. Seems like that's the way your problem started and it has gotten worse over time.

So, open the hood at night and look to see if you have sparks going everywhere. That's an indication of bad wires. And, pull the plugs and look at the insulator to see if there are tracks down them. Or a crack.

 

Yes, exactly that - fix the cavity.

You have a cavity in your tooth, code 12.

You have a headache, code 26.

Your jaw hurts, code 47.

Fix the cavity and all those things go away - that was the intention of the design.

Regardless, if it were mine, I would be focusing on that code involving the tachometer, as THAT is where your problem is originating. The bouncing tach is just a symptom and is reporting what the engine is doing, you need to find the cause.

 

Go back to what Gary mentioned... plugs and plug wires [distributor cap and rotor, too]. How old are they?

 

Thank you all for replying!

I decided to look into the coil and wiring for it. I got an extra coil from the junkyard just to see. Now granted the coil was an untested, unconfirmed part, I figured what was the worst that could happen? Well it started, ran, and still cut out. I then started looking at the wiring and saw this:


So I crimped a connector to tie them back together. Still did the cut out thing.

Quote:

Originally Posted by Gary Lewis

On to the wires/plugs. What you've described fits with a bad wire or plug. What usually happens is that the spark jumps to something else as the cylinder pressure goes up and makes it hard to jump across the gap. And cylinder pressure goes up as the load on the engine goes up. So, the load is high in top gear, but less at the same speed if you shift down. Seems like that's the way your problem started and it has gotten worse over time.

So, open the hood at night and look to see if you have sparks going everywhere. That's an indication of bad wires. And, pull the plugs and look at the insulator to see if there are tracks down them. Or a crack.

Yeah to a certain extent. I pulled all the plugs and they looked fine. Number 1 was kind of richer but numbers 2-6 where all reddish tan. I did not see any tracks, cracks, or particles on them. I also started the truck with no lights on and did not see any sparks or arcing anywhere.

Quote:

Originally Posted by ctubutis

Regardless, if it were mine, I would be focusing on that code involving the tachometer, as THAT is where your problem is originating. The bouncing tach is just a symptom and is reporting what the engine is doing, you need to find the cause.

Yeah I understand that. I filmed the tach so people could see what RPMs it was happening at. Plus I didn't want my ugly mug in the video polluting the Internet more than it already does!

Quote:

Originally Posted by 1986F150six

Go back to what Gary mentioned... plugs and plug wires [distributor cap and rotor, too]. How old are they?

I got this truck in December of 2013. I replaced the plugs, wires, cap, and rotor then. They probably have around 3,000 miles or so on them. Like I said earlier I pulled the plugs and they seemed fine. I popped the cap off to see what the terminals looked like. They had some buildup on them, so I sanded them a bit just to get through the buildup. I was trying to see if it was making a bad connection and then I'd buy a new one if it got better. It didn't.

Again I thank you all for replying. I'm thinking maybe I need to check the wiring from the ignition to the computer. I'll look for a wiring diagram and see what happens.

 

In my experience, this kind of thing has been caused by a failing ignition module or failing pickup module inside the distributor.

That bouncing tach tells you there is a problem with the Primary ignition circuit (the low-voltage stuff) and not the Secondary (high-voltage stuff).

 

i would next check the pickup in the distributor. As for wiring, here's the closest I have: Feedback Carb Control (ECU) - Gary's Garagemahal

 

It's like you guys are psychic! My brother and I thought we should mess with the pickup coil. I looked for a test, but came up kind of short. So my brother said whatever, we should just replace the distributor and return it if it didn't fix it. I objected, but he said he was buying it anyway. Alright then.

So, we stabbed the new distributor in. It idled so much better. I got excited, thinking finally! Well...that did not fix it. Though it idled so much better, it still had the high RPM cut out.

I then decided to clear the codes since we disconnected the SPOUT connector and see what showed up. Well, KOEO and CM codes were 11--system pass. KOER gave me 13, 21, and 41. 13 is an ISC one and 41 is system lean. I already had those but 21, which is ECT out of range, was new.

Seeing as I had an ECT code before in CM (51) and now had one in KOER, I figured it was time to test it. I found a chart for the resistances at different temperatures and started testing the ECT. We kept getting open loop on the multi-meter. We tried cleaning the pins, thinking maybe it was just a bad connection. That didn't help, we were still getting open loop. It also didn't matter if the sensor was hot or cold, it kept saying open loop. Ok, that sensor is bad. We got a new one and put it in. It didn't fix it, and oddly made the truck run rich. So rich I could smell it.

I had read when you replace a sensor, you should disconnect the battery for at least 15 minutes to clear codes and put the computer into relearn mode. I don't know if this is true or not, but figured it can't hurt. I disconnected the battery for 30 minutes just to make sure it would go into relearn mode. Once I restarted the truck, it seemed to idle a little smoother. I checked the timing and it was bouncing between 12 and 14. Not as high as it was, but higher than the 10 degrees static is has. Ok, time to drive.

It did it in third gear and fourth in succession and then didn't do it again. I was disgusted. When it didn't do it, I got to 3500 RPM in second and third and 2800 RPM in fourth. It runs great or really bad. I have no idea. It must be something simple I'm missing here.

I decided to check the codes and I got 11 in KOEO and CM. Then I got code 44 in KOER. Code 44 is AIR System inoperative. That was the only code I got. Someone at one point in time removed the AIR pump and the valves, but left the solenoids. The solenoids still have vacuum going to them and are plugged with bolts where they, I would assume, plugged into the valves or pump. Any way, it got late so I called it a night.

I am wondering if I need to drive it some more to see if I can trip a code besides 44 or maybe it fixed itself...doubt it, but one can dream can't they?

 

Someone once said these trucks are onions. You just keep peeling the layers and crying. Eventually you get them where you are satisfied - but there are usually still layers left.

Anyway, you've peeled some layers and know there are some left. So, I would drive it awhile and see what happens. But, I doubt you'll ever get everything correct when the thermactor system isn't functional. These systems are smart enough to know and get their knickers in a twist.

 

Crying is about right. When the truck is running fine I'm happy but disgusted beyond belief, almost to tears, when it is doing it's bad thing. But I am happy for now. Read on...

So after I gave up last Thursday night, I drove the truck out to dinner the following Friday. I kept waiting for it to do it, but it didn't. Cool, I can eat in somewhat peace. The drive back it wasn't as smooth. It did twice real quick at the top of third gear and then was fine. Stopped at the gas station so I could get another key cycle in. Drove home and it did it again at the top of third again, but only once. Alright, time to check codes.

Checked the codes and KOEO I got 11 and CM I got 14. KOER I got code 44. Again, 11 means system pass and 44 is Thermactor non-functioning. 14 on the other hand is Ignition pickup (PIP) was erratic. It seemed odd the remanufactured distributor had a bad pickup, but not that surprising. I've heard remanufactured parts from the chain stores only replace the obviously bad parts and leave the "good" parts. Seemed like what happened here.

We called the parts store and had them order another distributor since this was under warranty. It took them two days to get it in--I suppose because of the weekend. Went and got the replacement and went home. Now here is a piece of advice I tell people and should have followed myself: When you are at the parts store, check everything over really well. I was racing the clock to get there before they closed, so my mind was a tad excited to pay attention to the fact the new new distributor was missing the o-ring. The parts store was closed when I noticed this back at home. Luckily, I had an old distributor to rob the o-ring from that didn't break. Good to be a pack rat sometimes.

Stabbed the new new distributor in, timed it, cleared the codes, and took it for a drive. Success! The truck has never ran so good! I was able to get it to 4,000 RPM in second and third. Before, the most I could muster (that is if it didn't cut out) was 3,500 RPM. I'm probably pulling quite the vacuum since I have the stock one barrel at that RPM, but it will do it now!

I just drove the truck tonight and it is still running the best it ever has. No more cut out and and the most power I've ever had. I will drive it a few more days to be certain, but it seems like it is fixed.

As of this time, it appears the ECT sensor was bad and the pickup in the distributor was on its way out. If anyone in the future has this problem, those two items being replaced fixed mine. Again I will drive it a few more days to be sure, but it appears those were my problems.

Thank you to everyone who offered advice! This forum has been a wonderful resource the entire time I've had this truck. It will continue to be my go to for solutions and I hope to offer solutions to others if I can. Thanks again everyone!

 

You're welcome, Ernie, and welcome to FTE. It is stories like yours that provide inspiration to try and help people....

 

Great news!

 

Congrat's! Glad you aren't crying anymore.