I recently purchased an '86 F150 with the in-line 6 cylinder engine from my employer. I really like the truck, as it is the first time I have owned a full-sized truck.

Obviously there were/are maintenance issues. The truck was owned by someone that didn't believe in spending too much money on repairs, when bailing wire and duct tape were available.

For background, there are various hoses through-out the engine compartment. Some of these hoses are still connected to things, even.

The only real resource I have for mechanical advice for the various issues is my employers brother, who has worked as a professional mechanic for decades. While I have great love and respect for this man, his "heyday" was in the 1940's & 50's, and while he would be the first person I would bring a 1947 John Deere tractor to, I suspect that his level of expertise is limited to engines that were built before the words "emissions control system" were put together.

I have asked him about the problem of the dieseling my F150 does after shutting off the engine, and his advice has (consistantly) been to put the truck in 4th, and let off the clutch as I turn off the engine, so as to use the mass of the inert truck as a means of helping to stop the engine.

Which I have been doing for several weeks now, but I am concerned about long-term damage or wear to the clutch, drive train, transmission or even the engine. Sometimes this technique is pretty violent, and is also embarrassing when doing the technique in public. (There always seems to be a pretty girl walking by at the same time my truck is lurching and wheezing itself into dying.)

I have (keeping in mine how difficult it can be sometimes when dealing with certain personalities) "probed" my mechanical resource about what ELSE can be done to stop this dieseling and he always gets vague and says something about there being a way for air to get into the engine, and that I need to find out where it is and "plug it".

Today I made a special trip out to his place to see if he could help me and point to a specific area where I might look for this "air leak" and he although he was willing to help, once the hood was up and all the hoses were flaying around, he got vague again about the whole thing.

One thing I noticed was a large rubber hose that had a large metal cylindrical piece attached to the end, and this cylindrical piece mounted directly to the front of the carburator. (The metal tube where it mounted to the carb was about 1/2" in diameter.) It was all rusted, and my mechanical resource grabbed hold of it and started wrenching it around until it broke off. I asked him if this was the problem and he said "probably". When I asked him what it was he said that it was something to do with the emissions control system. He said it in a certain kind of voice that let me know that he didn't like, respect or understand the Emission Control System, and he advised me that the best thing I could do was to "plug it". When the engine was running, hot exhaust was blowing out this tube and would have been going into the carburator, if he hadn't broken the cylinder it was attached to.

I figured if I got the name of this thing, I could probably pick one up at Auto Zone, but when I asked him for it's specific name, he got vague again. He said something like "Exhaust Intake Valve". I asked him if this was a one-way valve, and maybe the reason air was getting back into the carb was because the valve was shot, and he said "probably" but all I needed to do was "plug it".

The engine still runs, about the same as it always did. Still diesels on shut-down. I am wondering how important this Emission Control stuff is to the overall "health" of my engine.

First, is it worth identifying all the hoses that are just hanging loose? Some are "plugged", some are not. Could any of these be the cause of the dieseling ?

I get the idea that getting this engine back to "normal" could be a long-term endeavor. But can I fix the dieseling situation first?

Also, I have run 2 16-gallon tanks through the engine (after I fixed the odometer, which also wasn't considered necessary) and I am getting about 12 mpg. Another F150 owner that has the in-line 6 engine tells me this is about normal. But I wonder about that also.

Could these all be related, the hoses, the dieseling and the poor gas mileage ?

If so, what should I focus on first ?

Thanks in advance for any assistance.


Billy

 

Hi Billy,

First off, I wouldn't let this guy near my truck again.

I think what this guy ripped off your truck was the EGR (Exhaust Gas Recirculation) Valve. I like to keep my truck stock and well maintained, so the 'You don't need it' argument has never held much water with me. If it were me, I would pull the air cleaner off the engine, take several GOOD digital pictures of all the vacuum lines and hoses, noting where they are routed and connected.

Go to your local parts place and buy about 25 feet of the right sizes of vac hose and replace them all (one at a time). There is a sticker on the front of the engine compartment that should show all the vacuum lines. Sometimes they are a little cryptic, so you might need to talk to a friendly motorhead to figure out if there are missing/misrouted vac lines. Replace the EGR valve, and then do a good tune-up. New spark plugs and wires, check the timing, new fuel filter and PCV valve, change the oil and filter, and maybe rebuild the carb.

I'd bet all this will fix your run-on problems. My thought here is to get the truck back to what it should be, then start fixing what isn't right.

 

Well, first off, check your timing, 10* btdc +/- 2*. If that don't help, you may need a carb rebuild. I believe the hose thing he ripped off was part of the air pump system, get it replaced. Don't go back to him, he is clueless.

 

Run on is usually caused by the idle stop solenoid not working. It is a small cylindrical
piece mounted at the carburator with one wire going to it, there is a screw coming out of it which hits the throttle arm . When you shut off the key the solenoid is deenergized and the throttle closes further then when the solenoid is activated, shutting off the fuel which causes the engine to run on. It is either not adjusted properly or it is sticking. Yes you need the EGR valve to be there and working.

 

Is the EGR valve a metal cylinder about 1 1/2" in diameter and about 1 1/2 inches long that has a 1/2" diameter rubber hose coming from the exhaust into it and it mounts to the front of the carburator by a 1/2" metal pipe ?

Maybe there is some place that has a photo of my carb so I can look at the parts and learn the names so I can talk/ask about them ?

I guess I could just go to Auto Zone, ask for one and see if it looks like what got pulled off.

If the EGR is shot, will that cause run-on ?

I just re-read all the threads. It looks like everyone agrees that was the EGR valve. I'll check the "idle stop solenoid" (if I can find/identify it) in the morning. (It's dark now.)

Thanks all, I'll report back when I am able to know/do more.

 

I went looking for a photo of an EGR Valve and found one on the NAPA web-site. Selected the make/model/year for my truck ('86 F150 XLT with in-line 6, in case someone wants to double check me) and found the the following:

http://www.napaonline.com/cgi-bin/ncommerce3/ExecMacro/NAPAonline/search_results_product_detail.d2w/report?prrfnbr=15536180&prmenbr=5806&usrcommgrpid= 75861679

I remember seeing this piece today. Its a different piece than the one that got pulled off. This is more like a "flying saucer", where the one that got yanked was mounted lower, and more of a "straight cylinder". I also remember seeing the little nipple coming off the top (of the saucer piece, which I think is really the EGR Valve). I noticed the nipple because there used to be a small hose coming from it when I got to the "mechanic" (he's really a nice old guy, BUT ...) and I don't think I drove off with the hose connected.

So maybe first thing in the morning, I'll try to figure out which hose USED to be there.

Thanks again, all.


Billy

PS
Oh yeah, they want about $75.00 for a new EGR valve.

 

You might want to consider buying a repair manual like Haynes. It should help you with alot of questions.

 

Seventyfive bucks for an EGR valve is good. Is it the Ford/Motorcraft brand? I would suggest spending the extra $$ and get an EGR valve from Ford, and not bother with off-brands. I replaced mine on my '85. The valve was $105.00 from Ford. I had a shop do it, so more than likely, the price was marked up. Good luck.

 

If you insist on replacing the egr then 75 bucks isn't bad. But alot of people pull the valves off a weld up a plate to replace them. Its a known fact to mechanics and those who build performance engines or evan build or rebuilt stock engines that the EGR tears the crud out of your intake valves. If you take a look at an engine that has never had an egr on it, the intake valves will be resonably clean. One with an egr will have carbon build up all over them. The EGR valve is also responsible for a loss of power at mid-throttle, because it lets the exhaust fumes back into the intake manifold.

All the hoses that run from the back of your valve cover (where the sensors are) to the front of the engine one goes to the smog pump, one to the EGR, and the 2 others are for something else (mine just connect to each other, thats how it was stock) They are not mandatory for your engine to run well. Most people who are looking for a lil more power or fuel economy would remove these anyways.

But if you want to maintain the factory condition then you need to replace every single hose.

That large metal piping that goes from the exhaust manifold to the front of the engine is part of the EGR system. Its what the exhaust comes from that is routed back into the engine. on the left side of hte engine there will be another metal hose that runs back into your exhaust system and comes back into a smog pump. I removed my smog pump when i changed engines, since the donar truck didn't have one i didn't use mine.

But if you want to maintain that factory condition then yes you need to replace all that stuff. Your truck will run just fine with your emissions control stuff on it. Thats how it is supposed to be.

But dont let them tell you that removing those parts will damage the engine. In fact its better for your engine to not have them. Think of how it was in the olden days before emmisions control. There wasn't any of that stuff. Look at how performance engines are built or look under the hood of someone who is looking to get what they can out of a stock engine. You wont see any of that stuff.

IF you want ill get you some pics of my engine without all that stuff so you can see what it looks like, or i can get you a pic of my buddies engine that has all that stuff still on it, if you want something to look at to go by.


whichever way you decide to do it. Just make sure you do it right. Replace all of those hoses and check for damaged wires and such.

dieseling problem usually doesn't occur from the fuel not shutting off. I can pin my throttle when i shut the motor off and it wont diesle is just shuts off.

I would make a timing check for sure.


if you want any pics PM me and ill get ya some

 

Today I lifted the hood and took a look. The EGR is there like I thought I remembered. The "flying saucer"-looking part. It has the nipple on top and no vacuum hose attached.

I think Jebadiah04 is correct about the part that got pulled off. It does come from first the exhaust and then a pump on the left side, driven by a fanbelt.

And I think you phrased the issue right. The choice is between restoring the engine back to the way it was built (expensive, and of unknown benefit) or start removing componants and basically do what the old man told me in the first place.

I am inclined to want to choose option "A", but the cost might be too much. The old man said there used to be a large cylinder mounted on the lower left side of the engine that got removed years ago. I think it he said it was something about (gasoline, I assume) Vapor Recovery.

Given that the truck is currently in a "halfway" state, I don't know which way to go. Plus, I don't really like the idea of pulling off components when I know for a fact I don't know what I am doing. I need this truck for work, and depend on it to run daily. It seems to me that the safe thing to do is to start putting stuff back on, re-hooking up hoses and what-not.

Is it worse to have the Emissions Control System "half-way" removed ?

Also, I looked for the "idle stop solenoid" today. I found a black plastic cylidrical piece mounted on the back of the carburator that had one (green) wire coming from it. It had a mechanical linkage to the carb. I fiddled with it, and noticed that the black cylinder rotated around the metal housing that held it to the carb.

That didn't seem right, particularly when I noticed that as I rotated it, the mechanical linkage caused the first butterfly valve on the carburator to close.

That shouldn't be, should it ?

I would assume that the "solenoid" action would be more direct, and not effect closing a valve on the carburator by rotating in a housing. And it felt real loose too, like the vibration of the engine might cause it to rotate and affect the carburator.

Also, I thought the first butterfly on the carburtor was the choke. Is the Idle Stop Solenoid supposed to close the choke when you shut off the engine ?

If so, then it all goes back to the old man telling me to find out how the air was getting into the engine. Maybe this is it ?

 

you were right, that black plastic thing with the wire coming out was the electric choke. now that it's been moved, wait until the engine is cold, then go out there, floor the accelerator, and look at the choke plate. it should be closed. turn it until it starts to open, then turn it back so it is just closed. tighten the three screws holding it on. what the old man likely broke off was part of the thermactor/air pump assembly, which isn't really necessary. if it's your only transportation, i would go with hooking it up basically stock. a chilton manual will help a lot with this. also, see if you can find someone who has one like yours...that's how i did it. unfortunately, run-on seems to be a built-in feature on those 1-bbl carbs. i would check your timing though, that's the biggest offender. then check the throttle solenoid...it's at the back of the carb on the passenger side, and has a shaft sticking out of it that presses against the throttle lever.

 

That black thing you were rotating was for your choke. You should set that back to where it was. Your motor should have a TFI ignition, no vacuum advance on the distributor. Which means you have an electronic feedback carb, that has a speed sensor. The speed sensor is located on the passenger side of the carb. It has a plug with 4 wires on it. It also has a plunger that contacts the throttle linkage and increases idle when you turn on the air conditioning. I think that is the only purpose of the speed sensor. Which may mean that if you do not have AC, you will not have a speed sensor. The speed sensor on my truck was not working because the computer under the dash was dead. The speed sensor performs the same function that an Idle Stop Solenoid performed on non-feedback carbs that were no longer used starting in 1984. I am pretty sure that California trucks were using the feedback/TFI system before 1984. The speed sensor has nothing to do with the choke. It just increases the idle speed when the AC is turned on. Those electronic feedback carbs are quite costly. If it also turns out that your computer is not working, I would consider changing the truck over to the Duraspark 2 ignition system used up to 1983, instead of buying another computer and another feedback carb. I changed my '85 over to DS-2 and she runs like a charm, and has no problem passing emissions. A mechanic I know who worked at a Ford dealership told me that the shop here in AZ has been replacing the carbed TFI with the Duraspark distributor, non-feedback carb, and a MSD 6A ignition module, due to emissions issues with the TFI systems used on the carbed trucks. You carb is probably shot. You are looking at 300+ for a reman feedback carb.

Try the link below for a picture of a speed senser for a 1985 truck. It should be the same for your '86:

http://www.partsamerica.com/ProductD...e=1179&ptset=A

 

Ok, no its not for your a/c lol

my 86 has one and it has no AC and never did.

What it does is actually senses where the throttle is and tells the computer when your at idle, its more prehistoric primative ford emmisions junk.

Sometimes they get old and get stuck and wont let your engine return to idle. common problem in these things.

 

tahts not the EGR but it is more emmisions stuff. If you look at the loooong tude that comes out of it, it will go back to the exhaust tubing by the cat. and then hook into about 18 different little gizmos and switches and stuff, and then up into a hugh Jass smog pump that likes to KILL power and gas miliage.

Im not even sure what the heck this thing does but it sure is a waist of hood space.



The EGR tube actually comes out of the exhaust manifold between cylinder 5 and 6 and up to the intake manifold right behind the "flying saucer" AKA EGR valve, and then inside the EGR valve its internally piped to the EGR valve and when the egr opens and closes it lets and restircts this exhaust into the engine.

You said it was unhooked. Ill run out tomarrow and post what color the wire was that hooksto the hose that hooks to the egr so you can hook it up if you want to. My advice and experience says leave it off. Even on a brand new truck the first thing i would have done is on hook the EGR valve so it wont open up. But if you are getting to much air into your engine it can actually be from the diaphram in the EGR valve being stuck partly open or being so worn out that the natural pressure of hte exhaust system holds it open. you can fix this by removing the egr flying saucer itself and making yourselfg a plate that covers the 2 holes under there perfectly and put a ghasket on it to seal it up good. If you do that and the truck runs good then you KNOW you are having problems with the EGR and then you can eitehr leave it like that or put a new EGR on. No point in waisting the 75-100 dollars buying a new one if you dont need it.

 

Wow.

I don't need a Haynes manual. Seems like I've got a whole crew of professional mechanics leaning over the engine compartment.

Paulz the link to the photo isn't working for me. I just fiddled with my computer, so I don't know if it's the link that is bad or my computer. Maybe there's an air leak in it too. I'll just have to "plug it".

Thanks, all, for the help.

Can I assume from the post about the electric choke that the "rotating action" of the electric choke is normal, and all I have to do is adjust it properly (thanks btw for the directions, I understood them perfectly), lock it down and forget it ?

As far as my next step on the "run-on" problem, I think timing it is going to be the fastest/easiest thing to try. The old man told me just to rotate the distributor until the engine started to die, and then rotate it back "a little bit" and that's all I needed to do.

(I had to replace the ICM a few weeks back, so I did what he said.)

I think I can afford (or even buy) a timing light.