Today I asked a mechanic friend at work, since I hadn't heard anything yet. I replaced the PCV Valve. He said, that it sounded like a power valve has gone bad in the carb. He also said that it sounded like the EGR may be bad. So, this weekend, I will be rebuilding a carb (AGAIN) and cleaning out the EGR. I may replace it all together. I have an inline filter in, it will be changed out again. 3rd in about 3 weeks. I did put it in before the fuel pump so at least I may be ahead of the game there.

Thanks for the reply.

 

Had the same problem with 86 5.0 4-speed Bronco for two months. Changed everything from wires & plugs, distributor, all the sensors and engine management relays and fuel regulator, fuel filter and both pumps. Nothing solved the problem it just slowly got worse until I pulled the fuel reserivior and found to my surprise a small fuel fuel, thats not mentioned in my manual, Well this $5.99 filter was so dirty I'm surprised the truck would run at all.Changed it today and we are back with full power, runs great for 139900 miles.

P.S. Dealer wanted $23.00.

 

Where do I find this small filter that you speak of? I have a 4.9l L-6 with a 1 barrel carb., is this going to have that tiny fuel line that you are describing?

 

On my bronco it is in the fuel reservoir, plastic can between the fuel tank & fuel pump beside the transfer case covered by its own skid plate. The bottom screws off like a canister oil filter. You will need a oil filter strap if yours is the same as mine. the filter is 1.5 inches ht. by 2.75 inches dia. and comes with a new o-ring seal. Carefull installing as I broke the o-ring and had to use the old one.
Hope this helps and is in fact your problem.

 

I am having a problem similar to this. My truck sat for almost 2 years due to the TFI dying on me. Once it was replaced, even with gas that sat for 2 years in the tank, she fired right up and ran. I ran both tanks with additive in them and refilled them to clean out all the garbage. Then I replaced the fuel filter on the frame. I have been driving it now for 3 weeks and have noticed a surging when I try to accelerate or climb steep grades. I was thinking it might be a tranny problem but after reading this I am hopeful it won’t be that serious. I am going to invest into a code reader because even after 250,000 miles on the original engine and tranny she just seems to want to be kept in the weekly rotation. I will let everyone know as I get deeper into this experiment, what the outcome is. I am also going to replace the canister filter that you were talking about, that is after I get the rusty bolts lose and can access it around the skid plate... Thanks for all the information....


By the way:
1986 F-150 4x4
Fuel injected 5.0
Overdrive 3 speed automatic tranny

 

Well here we go. I went and bought the code reader from Wal-Mart. It passed the diagnostic (code 11) and came back after the code 10 with a code 31 on the continuous memory check. I reset the computer on the truck after the test by removing the battery cable for 5 min then reattached the cable and ran the truck for about 25 min. It seems to be running better but I can be sure if running the test and resetting the computer can have that effect. This is day one of running it so I will keep posting any changes. I do plan on changing the canister filter soon, but was wondering if I should still replace the EGR valve control sensor? Also in the code reader manual under code 31 for the continuous memory says “(EX Trucks).” I take this to mean except trucks. Am I wrong here?
Also after I ran the truck I reran the diagnostic and it repeated the same return Code 11-10-31. I will run it a little harder on the way to work tonight on some of the inclines to see if the surging still happens under load. If it does I am thinking of the canister filter replacement and cleaning the EGR. Any other suggestions folks???
Thanks for the help everyone…

 

I reset the computer on the truck after the test by removing the battery cable for 5 min then reattached the cable and ran the truck for about 25 min.

It should be for at least 30 min. drive it for 10 miles in different driving solutions (stop an go etc)

Code 31 is an EGR fault, if you get a 11 then a 10 (means a seperator before the next code) then a 31. and the code reader will stop at 31 unless there is another code.
EGR may need cleaning, be sure to get a gasket for it if you do clean it....I had replaced mine with a new one, and gotten the same code again as you did..but my air pump isn't connected and the air tubes from the exhaust had been removed...the heads has big plugs in them to seal it.

 

It was about a 20 mile drive on a country back road with plenty of variation including speeds of up to 60 miles per hour. It did seem to run fine on the way to work tonight. I am suprised that I have not had the hesitation on the way due to 2 inclines that usually produced it. I will continue working on it over the next week or so.

 

Ok, I changed the hidden fuel filter in the canister, and that was a help. Today I found that if I apply vacuum to the EGR valve with it NOT running, it stops the steady code indicating there is an immidiate problem. I replaced the O ring gasket between the EGR valve and the EGR sensor on top and it seems to hold vacuum better now. Maybe I'm not getting the vacuum I need with it running? I'm tempted to put my old egr valve back on, I think they are both ok. It looks like a vacuum problem now. Now, is there a way to block off the egr and still have the truck pass emissions? I've heard about the disc under the EGR to block the gasses, but I don't know if it would still pass emissions testing.

Also, does applying vacuum to the egr open or close it?

 

Applying Vaccum to the EGR opens the valve, its not suppose to be recieving vaccum at idle except when the sensor tells it to (opens the valve).

 

Ok, so it looks like the truck dosn't like having the valve closed with the engine off. I guess it's supposed to hold it's vacuum while your parked. (it still isn't after my gasket replacement) But if the valve dosn't want to open why isn't the truck performing? I'm thinking of just plugging both ends of the vacuum line and seeing what it does.

 

ok, this thing was really starting to tick me off on my way home today, and I'm not proud of it, but I went ahead and plugged the vacuum line on the egr valve. I havn't driven it yet, we'll see. I don't have to go to inspection for another year, so I'll worry about that then.

 

Mine turned out to be a carb problem. I was actually missing pieces on the fuel metering rod. So that has been replaced and the jets adjusted and it is running much, MUCH better now. Still not a lot of excessive power though. I am considering the next upgrades and thinking that I will have to go with a modified intake manifold, headers and a 2 bbl holley. Screw this little 1 bbl carter.

Thanks for the reply though.

 

I'm not sure my story will help but you never know. This is on my 1986 302 EFI/AOD. I had this similar hesitation problem when accelerating. At first it felt like a sputering/hesitation, then it grew worse and felt like I had a heavy trailer pushing me back and forth and finally it got to the point where it felt like someone was cycling the ignition key very fast between the RUN and OFF positions. I replaced the O2 sensors twice, the spark plug wires, the TAB/TAD, the MAP sensor, the DuraSpark box 3 times, the EGR valve twice, cleaned the throttle body several times, cleaned the EGR valve too many times to count, replaced vacuum line to the EGR, replaced all spark plugs, drained the fuel tank and changed the air and fuel filters, tested the fuel pump, checked the FPR for correct fuel pressure, had the injectors cleaned twice, replaced the TFI module 3 times and replaced the distributor cap and rotor and finally replaced the whole damned distributor assembly. Lots of money wasted. It still did the same thing. Every time I would mess around with components around the distributor and EGR valve, the problem seemed to be temporarely fixed but it would come back with a vengeance. I took it to 3 Ford dealers, no one knew what it was. Finally, I would be driving around, hit a bump on the highway and the engine would shut off. It would crank but not restart until I found another bump and then, most of the time, it would restart. Interesting but unnerving in traffic. Then one day, I had the engine on, hood open, and my wife was helping me find the problem. The TFI module on this thing wasn't on the fender well but mounted with two screws to the distributor. She grabbed the TFI plug wires and the engine died. We figured out that there was a break in the wiring to the TFI module! You could wiggle it, get it to die and wiggle it fast again and it would continue running. I replaced as much wiring as I could that had to do with the ECM, DuraSpark and TFI module. I got all the connectors from Ford which had about 6 to 8 inches of wiring to do the splicing with new wires. This is why messing with the EGR and distributor fixed it, it would move the TFI pigtail just enough to restore connection and engine vibration over time undid everything again. Some of the TFI module wires carry the START and RUN signals. I don't know if this will help but it's better than nothing.

 

Thanks for the reply. I took the truck out again and it seems much better with the vacuum to the egr disconnected. I have been getting an EGR code long before the problem, it wasn't until the problem started that I began repacing parts, but the code and problem wouldn't go away. Maybe I have a break in the wiring to the EGR valve, that might explain it. I wonder if it will pass emissions like this? Actually, even though it wasn't performing well, it would probably pass inspection with it reconnected next year when i have to worry about that, then just disconnect it again.