Your problem is carb icing. On cool damp days when the fuel atomizes it acts like a refrigerant and freezes the moisture in the air stream in the venturi I have had this happen on my 84 300 six yf carb. The first time it was the little damper on the end of the air cleaner was bad causing it not to bring warm air from around exhaust manifold. It causes it to choke down real bad. It is next to impossible to run cold air throught this carb without this happening. The only cure is to make sure that heat riser is working and that the warm air intake system is intact and working and insure the motor is coming up to temperature.They are notorious for this and it is hard to diagnois. Usually if you pull a plug out just after this happen it will be nearly black from running to rich.

 

garbz2: Thnaks very good possibility. I would hope not with the carb being rebuild by prof shop <1 year ago but...I'll check

O2 sensor suddenly reads lean and feedback dumps more fuel in to compensate..."
I heard this in another post and has me befuddled. How does the computer do this? Does it do this somehow via the feedback solenoid otherwise it is a carb??


sail2244: Great idea about checking the computer via the timing b/c I believe if the computer is doing something to screw things up (from some bad input) it would affect the timing. Now if I could only do that while the prob is happening

ok, re: idle actuator...now I knew it did that but others have been posting about the TPS...that's not the same thing is it?? B/c this truck doesn have a throttle position sensor that I can tell.

Pretty sure most of the connections are good all the ignition (TFI, LT, etc) wiring plugs checked good as well as everything connected to the carb when I replace that stuff (not too long ago) and I used Oxguard (cond grease) at that time.

wtroger: Thanks I had been thinking something like that but when I've had the problem, pulled over, pulled the aircleaner, the choke is wide open.
Also pulled hose off of air horn so either way pulling in air from under hood (while weather is cold)

Checked the small battery ground cable, its good. (mentioned b/f as possib)

Hoping to get codes tonight...Snow and roof leak(house) prevented earlier
Also hoping to find a place to test the coil (dynamically) (mentioned earlier)...then again might just buy a new one

Thanks again

 

Ok, I finally had some time and reasonable weather to do the more involved checks.

I'll lisit what was done in order to be slightly more brief. These the most probable potential problems that you guys had suggested:

-Checked most of the connectors that I hadn't checked previously and a few that I had.
UPSHOT => there were no problems with corrosion or oxidation in any of the connectors. The only connector that was somewhat questionable was the temp sender and I cleaned, Oxguarded and replaced.

- Temp sender could be bad and it was stated that this would be an instant "open loop" situation for the EEC-IV computer
UPSHOT => Externally heated the neck where the ECT is mounted and watched the Resistance go from near infinite to ~5K ohms. Now my manual doesnt' have the values that it should read but at least it isn't open and it does change as it warms as to be expected. So not the "magic bullet" to my problem
Anyone know the values for the ECT??

WIggle the carb body and verify if loose...can be a cause of vacuum changes and cause loss of power, bucking , major fuel consumption (??) that I have seen
UPSHOT => It was tight no problems

AND THE ONE YOU'VE BEEN WAITING FOR...
Pull codes off the EEC-IV computer. Now I can't believe Ford when then designed this system would leave these exposed plugs near the battery but I guess they had some reason??
After cleaning up the connections with contact cleaner and then applying Oxguard
ran the test as outlined in link (listed above)provided by tmcalavy Thanks again!
UPSHOT => I got nothing the VU meter would climb to 12v and then hang there??
Know I have a question regarding how the link describes the test (on Pg 2 far right diagram #2) I hooked up as shown in diag #2 and then tried to get readings: 1. grounding the STI and also 2. not grounding STI
Either way results were the same... the meter would climb to 12V and than hang there. So, I then tried the KOER(Key on engine running) tests...nothing different

SO....
I tried the test that sail2244 suggested (thanks!) to run the engine, hook-up timing light and rev engine and verify that timing advances
UPSHOT=> THE MARK STOOD STILL! ... no advance at all

So, I guess that in certain conditions this is causing the engine to loose power, then buck and run rough...I think that the carbon build up gets to a point and then this occurs. ALso believe that is why I don't see it happen on short trips around town but longer trips (which include highway driving)...but then again sometime it doesn't ?????

Do anyone know if there is a way to test the computer outside the vehicle? I believe that the computer is bad. Not the TFI (?)

Does this seem like the correct analysis and do the conditions I have occurring match this??

Thanks again to everyone.

 

straight6: Sounds like your original assumption was correct, that you are running in open loop mode 'cause the EEC isn't working. In my case (identical to yours), it was the EEC ground from the battery cable wasn't connected when the cable was changed, as I mentioned in a prior post. Interesting thing is that these trucks will run with the computer disconnected....or the control relay removed. Not knowing the history of the problem, just started, always there or what, it's a little difficult to say. The EEC is under the dash, just above the steering column and to the right....the control relay is mounted on a bracket next to the EEC; you might check to see if they are both there and plugged in. If the truck suddenly goes into open loop the idle jumps up to 1500+ rpms and the timing remains at the static setting because the computer can't feed in advance settings any longer. The feedback carb also defaults to a rich setting so you lose power, gas mileage goes in the dumper and they usually diesel when you try to shut the engine off due to the fast idle.

Hope this helps,
Brian

 

Couple things I guess I should have posted before going under the assumption/suspicion it is the EEC-IV I did remove it....So to answer you question Brian BJ...

The computer and relay were connected but if I'm in open loop mode, the idle does NOT jump to 1500 rpm other than when I start the truck cold...once warm she's steady at 600rpm....other than when the problems occur

Q: (Brian BJ) what do you mean the carb goes to a rich setting? How's this done...via the feedback solenoid??

So that's my point in previous post....Do the conditions that I"m having match what I've found??
Runs fine and then at random times while on a longer trip (i.e. sustained driving 30 miles+) she'll start to loose power, then fairly rapidly start to missing or "sputter", then buck during this time she'll blow some carbon in the exhaust(i.e. darker...not black),start sucking fuel ...pull over fiddle w/ stuff/ wait a bit then steady idle will come back, blip the throttle (responsive = power back) blows out black smoke (carbon) drive down the road fine for some period....go to the beginning and repeat

Could this be the EEC? only?

 

straight6: I'm no expert but....I'm learning every day. I suspect you may have two problems. The feedback solenoid is modulated by the EEC at a rate of around 10 pulses per second. When the engine is running, you can hear it ticking with use of a stethascope or long screwdriver, piece of tubing, etc held against the solenoid body. The solenoid is located at about 4 o'clock, viewing the carb from the top and you standing in front of the bumper. The solenoid controls the air/fuel mixture to some degree.....about 10% from what I read somewhere. If it fails (or the controlling signal from the EEC fails), then your fuel mixture goes rich because you have lost a portion of the air bleed into the idle and main fuel metering circuits. I can't prove this but I think the oxygen sensor sends rich/lean signals to the EEC, causing the varying signal to the feedback solenoid. Makes sense to me, anyway. If any knowledgable Ford techs are reading this, please chime in....

If you system is in open loop, indicated by not seeing any timing variation, then your idle should jump up.....unless a dreaded prior owner has twiddled with the DC-ISCA, (DC Motor Idle Speed Control Actuator). This is located at about 11 o'clock on your carb, again, viewed from the top. This is a DC motor, used for anti-dieseling shutoff, high-cam RPM, dashpot and pre-positioning the linkage for the next vehicle start. It also contains an integral Idle Tracking Switch (ITS).

These trucks with the EECIV run pretty well when everything is right with them....as has been said before, they don't like to be tweaked but you don't sound like a tweaker.

I suspect you may have two problems.....perhaps a sticking float in the carb and EEC inop. I actually had a similar blubbering and flooding problem on my '84 which didn't occur until it was warmed up. I kitted the carb (not my first one....I'm 60 years old) but to no avail. A Holle rebuilt carb took care of the problem and all is well. Wish you lived closer, I'm in Oregon.....

Brian

 

Brian thanks for continuing to respond...I really appreciate all the help and thanks for the offer.

"unless a dreaded prior owner has twiddled with the DC-ISCA, (DC Motor Idle Speed Control Actuator)"

OOPS I'm guilty as charged! You're right on the money! You are also correct, I'm not usually a 'twiddler' (i.e. look for a go around) b/c I'm more of a FI guy other than the carbs on my motorcycle....which btw are amazingly steady in comparison.
Anyhow, I was previously fighting the idle and not having a good manual, previous to me knowing of this forum, and a little at wit's-end I screwed with (literally) the adjustment on the DC-ISCA b/c it had an high idle. (1000-1300prm)

Q: Other than turning the adjustment screw back are any know ways for proper adjustment of the DC-ISCA?

So to be clear, I'm not getting advance when I rev the engine and the idle is high

Q: So, I've got the computer out of the truck. Can it be tested that way by Ford shop?? Since we believe its bad but it would be nice to have a definitive test

Q: Go to Ford only for a new EEC-IV or have people had good luck with rebuilt ones from auto parts stores?

I'll be surprised if its a sticking float also considering that I had the YFA carb rebuilt by a prof shop ~9 months ago. Can the float just get stuck and unstuck easily?? i.e. just pulling to the side of the road couple mins at idle??

Q: Is it possible that only the computer is causing this and not the float?

Thanks,

Brian aka straight6_nh

 

Brian: Another holder of the sacred name, eh? Well, since you have the computer out, you could drive the truck to try to see if the blubbering condition remains. It will run and drive without the computer but, of course, will be in open loop mode. I'm sorry but I don't know if there is a parts house who can check these.....I've heard that AutoZone can check a lot of electronic parts such as the TFI module on the distributor but donno about the EEC. If you have one close by, I guess a call would be in order. Anyway, driving it could tell you if the intermittent over-rich condition were the EEC trying to work once in a while or coming from somewhere else.

I am luckier than most because we have a half-dozen or so "U-Pull-It" wrecking yards in the Portland area so I was able to score a matching number EEC and relay cheap....about $20 or so. These trucks are nearly bulletproof if all is working but can be a bugger to troubleshoot if they are not. I bought the Ford manuals for '84 on ebay and have picked up a couple of other manuals, one a Chiltons and one on CD. The Ford manuals are, of course, the best but are somewhat intimidating just because of the sheer size and amount of information...the stack is probably 6 inches thick. They also call out using Ford Rotunda tools but often a VOM can be used if a guy is savvy enough to extrapolate the information.....which I think you are.

Once the EEC is working, you can then pull codes which will not tell you how to fix the problem but will get you into the area at fault. As far as the ISCA, I could scan the adjustment procedure from the manual and send it to you but I really don't know if it would be identical to your truck or not. I have heard the EEC relays also fail.....this isn't just a simple relay but also has a timedelay built in to hold the EEC energized (at least for certain functions) for 10 seconds after the key is turned off. That 10 seconds is used to dontrol the ISCA and the Fuel Bowl Purge Solenoid which allows excess fuel in the float bowl to go to the Evap Cannister. May be other functions that occur during that 10 seconds that I haven't learned yet.

One thing I noticed in an '84 Electrical Troubleshooting Manual was a couple of fuses in the fuse block......Fuse 6 fuses a lot of stuff most trucks don't have but also fuses the feedback carb control. Fuse 18 also fuses a lot of stuff most trucks don't have but also fuses the EEC. Whether this is true on yours or even on ALL models of '84, I don't know that either.

I do know these trucks are very sensitive to grounding and there are a load of ground points all over the vehicle. Sorry if I'm kind of wandering here, just that I'm still in the steep part of the learning curve on these rigs myself......only had my '84 since August. I drove an '84 E150 with the 6 for many years but other than changing oil, plugs, etc, I never had to get into the thing at all. Had 207k and still ran well when we sold it.

Sorry to be kind of vague here, we be tryin'!

Brian

 

I replaced my YFA carb with one for a 1975 300 six. Nice exact fit, and the gas mileage is much better. I set the timing by ear and it gets decent power now, too. The computer in this truck fried years ago, and has not worked in the entire time that I have owned this truck. I recently took a 6 hour one-way trip to Ohio in this truck. Ran great there and back. Fords ROCK!

 

Brian thanks again and no worries re: "wandering" all ideas good. Holmes Thks had thought of that but last resort.


Well I was ahead of you on the whole autozone and boneyard idea for an EEC-IV

I've deduced from the autozone website (quite good btw) that 83-86 EEC-IV *could* be swapped. Given that, there is little chance I'll find it in the boneyards around here. One right up the road (convenient) has only newer trucks...sort of ironic which is pretty much they way it is around here maybe b/c the weather.

Called Ford this am and they said no longer carried for an 86 they also said no way on the out of truck test of the EEC.

Autozone does sell rebuilds as you mentioned for ~$100 with a core charge. I was sort of taken aback when I saw the array of computers available for just 1 year of truck (well over 10!) Gotta love Ford.

I'll check the fuses 6,18...all to be sure...good call.

Q: So, anybody have any ideas that would lead me to believe that the EEC-IV is still good if no timing advance when truck is rev'd??

Brian, if you could quote a reference on the proper RE-adjustment of the DC-ISCA that would be great!
Everything was tested,adjusted, and replaced if needed when carb was rebuilt so I expect everything to be good there.

Thanks,
Brian

 

Haynes has a step-by-step walk through for checking the computer. First things are to check power and ground through the connecting harness and the manual tells which pinhole(s) it is/are. It also talks about testing/replacing the EEC power relay, because, well, no power...you know . Then there is a way to check internal ground as well. Your trusty volt/ohmeter earns its price with the troubleshooting you're doing. The power relay cost me about $20 to replace and I still had nothing (The old one was bad, but a new one didn't help because the computer itself was bad ,too.). Replaced the EEC with one from the parts store 17 months ago and all is well. But I'd hate to have you go buy a $100+ NON RETURNABLE part and have it not help. Especially to find out it just wasn't working because it didn't have power or ground!

Called Ford for the EEC -- that's a good one. I did that, too. They didn't even want to talk to me. "That's an obsolete part... Click!"

Yeah, I think it could be the computer and not the float. If it were the float, I would expect symptoms either all the time or randomly if the problem was intermittent. Now, I may be misunderstanding, but it sounds like you only have the symptoms after a period of steady cruising. Not with stop and go, not at idle. Which brings me back to the EGR system. The EGR is supposed to be open at steady cruise. It closes at idle and at wide open throttle. See the correlation? On our trucks, the EGR sensor tells the computer the valve state and the computer controls the opening and closing via solenoid that allows vacuum to pull the valve open or not. I think this was developed because earlier EGR systems were directly vacuum controlled, so they just put the computer in control of whether the EGR sees vacuum or not. If the EGR isn't open at cruise, *I think* that can make the engine run too rich, which, after a while at relatively low RPM cruising might begin to load up the combustion chambers with carbon, fouling the plugs and causing your missing/bucking. Once you let it idle for a bit at a proper mixture, the fouling burns off, and the engine smoothes out. Now, I don't think there is anything wrong with your EGR valve or sensor - I think it is the faliure of the computer to control the system that is the problem. You could check the EGR valve and sensor to make sure, if you want, but I think you end up back at the EEC.
Why does it sometimes not do this? I'm guessing that if traffic is heavy or you are driving more agressively today you are less likely to have trouble, IF my above blind speculation is right . WOT (passing someone, stop-and-go) will help prevent the loading up, so you go for many more miles without trouble when driving hard than when at easy cruise. Again, I'm guessing here, and you'll be able to observe the pattern if its there.

I've got my fingers crossed for ya (and its darn hard to type this way) that it turns out to be a failed EEC power relay and your computer is just waiting for some juice! Better $80 in your pocket then the part store's.

Peter in Portland

 

Brian, I don't want to hijack your thread, but I do want to give a quick shout to Brian BJ.

You may not be an expert, but man, it sounds like you are headed in the right direction to get to be. If I'm straying out of the ballpark, feel free to correct my erroneous ways. The last thing I want is to cost Brian time and money based on something stupid I said.

U-Pull-It is cool, but the one in Vancouver converted to an FAP. Won't let me in the yard anymore. Of course, that's the one I live about 3 miles from.

Thanks Brian

 

castman: Thanks for jumping in here with some really good points regarding troubleshooting inputs and especially the EGR stuff. For some reason, EGR systems are an area I've not been into much...just very lucky I guess. Now that I've said that, probably all three rigs I own will develop them! I'm very familiar with the yard at 5 Corners, I lived up there from '70-'80 and they were a good source for the old beaters I like to play with. FAP owns U-Pull-It if I'm not mistaken. Nice to meet you here.....

Brian: I'm digging out the factory manuals to find the setup for the ISCA and I can give you the pinouts for the EEC if you don't have a Haynes....

Brian BJ

 

Thanks again guys!

Castman: Good idea on the power relay I was beginning to think that also so I already pulled it last night.
Q: Now the question is can I test it like any other relay or is it just better to buy a new one and skip to the next step?

Brian: Thanks re: looking up the info(pinouts and setup ISCA). I don't have the Haynes or any other decent manual. I've been using the Chiltons...you know...
1900 to....Ford every truck manual I've been looking for a good one though.

straight6_nh

 

Ok, I've ordered a rebuilt computer from AZ but I still had a little bit of a sinking feeling like Castman said... is this going to fix it?!

Castman: no prob re: hijack...also thanks for the ideas
Your idea: check fuses UPSHOT=> ALL checked fine

Q: Is the EEC-IV fused anyway??

Your idea: get/check the power relay
UPSHOT=> Brought to work today and tested on our test bench...Checked good.
I pulled the top off and I could see and hear the contact open and closing as I removed the 12v.

Btw, after you post describing how much info is in the Haynes I think I'm going to buy today... I can't find any used Ford manuals for sale and it seems that many like the Haynes...
Q: Is the "Ford - Pickups and Broncos" the one that is recommended?

Castman also wanted to say that your "driving description vs engine reaction" is right on with what I've found.
When the condition occurs its usually happens on the highway portion of my commute(cruising...yielding more carbon buildup). I've never had it happen around town i.e. stop and go, acceleration yield less chance for buildup and closer to proper mixture. ALthough I've exited the highway with the problem and it still there until I pull over and let idle which initially it will hardly at all do then settles out and then blip the throttle, you can feel the engine is responsive (opposed to before lots of pedal no go) blows out carbon continue down the road until condition sets itself up again and repeat.
The other variable that makes things worse here and also agrees with the two conditions we've talked about is that b/c the engine is not advancing (i.e. running w/retarded timing) it runs colder (makes sense??) which only makes the carbon situ worse and agrees with the 2 driving scenairios. I've had to block near half of the radiator which has raised the temps (now mind you it has been COLD in NH lately too) which has held off the problem somewhat. Makes sense too higher temps should yield slightly less carbon build up (right?)

Thanks again but it looks like I'm in for an EEC unless someone has any other ideas??...Yes, I'd like to not have to spend 100$ but I don't mind spending it if IT IS the solution. Although, I do weigh up how much I spend, I dont want to spend good $ after bad.
I've toyed with taking the "easy way out" and doing the Duraspark thing but the more I've worked on this Truck (owned for about 1 year) I've found that pretty much everything is there /intact so try to keep it. I'm just hoping I get to a point where I get the reliability these straight 6 Fords are known without having to spend a fortune. That was the reason I bought this truck.

Straight6_nh