Code 31 Help

[CavScout0]

I have an 85 Bronco II that has me chasing this code 31 all over the place. I get the code during key on engine off tests. I have replaced the egr and the evp sensor. I have checked the wire from the evp sensor to the ECM and that checked out ok. I figured it was the ECM and replaced that. No change. I have ohmed the egr vacuum solenoids and tried several different sets of solenoids and still have the code 31. What next? I am at the end of my rope. Is there anything I may have over looked? Is there a Ford step by step troubleshooting guide anyone knows about? Any help would be greatly appreciated.

 

[jhammel85]

Did you check the voltage at the evp? Check that out along with its connectors.

 

[kimcrwbr1]

Connect manifold vacuum to the egr while the engine is ideling. The engine should stall? If not confirm the egris opening by sticking your little finger up underneath the diaphram you should feel it pull up. If it pulls open and the engine stays running it is probably the exhaust ports plugged in the heads and the intake manifold for the egr. These motors are notorious for bad valve guide seals and the carbon plugs the egr ports on the heads. Does your engine puff black smoke when you start it? When doing the KOER test the computer expects a response in rpm when it opens the egr. The only cure is pull the intake manifold and clean all the ports and put in new valve guide seals.

 

[kimcrwbr1]

Another common problem is check if the egr has vacuum full time if so the air bleed circuit is plugged somewhere. The orange tube from the solenoid closest is the air bleed tube and is what allows the egr to close. disconnect it from the air horn on the carb and feel if it gets engine vacuum when you give it gas. The reason it is plugged into the bottom of the air horn is it pulls in fresh filtered air when the computer closes the egr. Again with your little finger you should feel the egr diaphram move when you give it gas and the let it idle?

 

[kimcrwbr1]

solenoid closest to the firewall

 

[CavScout0]

Yea I checked voltage at evp and was getting 4.8 volts coming in evp and .5 volts leaving evp to computer. I dont think the code has anything to do with vacuum as the Key on Engine Off test there is no vacuum. I think it has something to do with the wires or the EGR Vacuum solenoids. I tried to trick the computer to give me a code 34 by taping down the pintle on the evp to read too much voltage but I still get the code 31 even though I was getting more than 4 volts leaving the EVP sensor. I ohmed the signal return wire going from evp to computer and got .01 ohms so there is no short even with wiggle test. And I cleaned the 60 pin connector and evp sensor connector. I think it has to do with the egr vacuum solenoids but have no clue how to test. Thanks guys for the input thus far. With your wisdom hopefully I can overcome this issue.

 

[kimcrwbr1]

Just checking here are you erasing the memory and then resetting the computer before you start testing. Have you tested that the egr is actually working. When you apply vacuum pressure to the egr at an idle the engine should stall. I fought with the code 31 it seems forever until my truck got old enough to do the duraspark. I tried the refurbished computer same problem, solenoids, sensers, egr, tps, map, O2, knock ect, act. It was when I did the valve guide seals and intake manifold gasket when I found the egr port on the heads and in the manifold welded shut with carbon buildup. I even tried grinding the tip off the egr senser to lower the voltage you will see it drop if you pull the senser off the egr. I never did try testing it with the senser off and plugged in to see if that would lose the code. GL

 

[CavScout0]

I would love to do the duraspark conversion. But, I am poor and my bronco II has the a4ld auto tranny in it. From what I hear the conversion with my tranny can be a pain in the butt. Thats why Im trying to get what I got going good for now until I have the cash and time to hopefully do a 4.0 swap. I am at a loss of how to fix this code. Im thinking it has something to do the the egr vacuum solenoids and feedback to the computer. I will check the wires going from the solenoids to computer and see what I can find

 

[kimcrwbr1]

What is the performance issues your having. You can do the duraspark conversion for around $130 with new parts and just hook the overdrive up to a switch on the dash. You can use the stock feedback carb until you find a replacement and just hook the vacuum advance up to manifold vacuum. Ideally if you find a late 70s mustang II, pinto or capri with the 2.8 it will have all the parts you need. I just bought mine at autozone, Module and distributor cap and rotor. Use the stock coil and carb and I got the harness for the distributor off of a 1984 ranger with the four cylinder 2.0. That mess of wires and vacuum hoses goes away on the engine. Sorry to say it but you may never shake the egr code and what it does is throw the computer in limp mode so it is allways running on base timing. Like a turd. You never did say if you tested the egr? while the engine is running are you getting vacuum pressure at the egr at an idle. It should be fully closed then pull the vacuum line off and put your tongue on the hose going to the egr and give it gas it should give vacuum pressure and when you let off the gas it should have none. The two solenoids for the egr are closest to the firewall the first is the air bleed and goes to the top of the carb pulling in ambient air. If you have it plugged or the line is plugged the egrwill not close properly. The computer closes that one and opens the second one to open the egr you should hear it clicking when you give it throttle and when you let off the throttle the first solenoid opens allowing air into the egr valve to close it.
http://i.ebayimg.com/t/1975-1979-Motorcraft-Carburetor-F2-2150-Bronco-F150-F250-D7TE-AKA-Truck-75-76-77-/00/s/MTA4MFgxNDQw/z/35sAAMXQhuVROLVK/$(KGrHqF,!iMFD)meJw+1BROLVJ8n6g~~60_14.JPG
I hope this works the egr air bleed tube goes to the large nipple on the bottom of the air horn that comes down is about a 45 degree angle.

 

[kimcrwbr1]

http://www.ebay.com/itm/1975-1979-Motorcraft-Carburetor-F2-2150-Bronco-F150-F250-D7TE-AKA-Truck-75-76-77-/221218873806?pt=Vintage_Car_Truck_Parts_Accessories&hash=item3381ac21ce&vxp=mtr
If you look at these pics it is hanging down next to the choke pulloff pod.

 

[CavScout0]

The main thing Im experiencing is the vehicle running rich. The truck idles just fine no smoke, stumbles or anything. Just runs ruch. Until today I was dinking around with it and it got put back together after more probing around tring to figure this code out. Well truck start fine and idles fine for a min or two. I push on the gas to give it a rev and it dies on me. I start it back up and now I have smoke billowing out the exhaust. White, grayish with a hint of blue smoke. Truck still idles fine and now the throttle is responsive. I have only driven this truck 3 miles maybe. Its been in my garage for a couple months while I have fiddled with it. Well anyhow I had this happen before when I did the Key on Engine Running test. Same thing, car ran fine no smoke and when I did the goose test smoke starts coming out the exhaust and woulnt stop. I think the only thing that cured it was taking of egr and cleaning it. And when I stomped on pedal it stuck open somewhat? I did check and was not getting egr vacuum at idle but didnt check the other test you suggested yet. Will try tomorrow. I thinking about just blocking off my egr. I absolutly cannot figure this code out so why not just block it off. Ohh the solenoid closest to my firewall is for the TCP according to my vacuum diagram with a vacuum hose connected to the front of the carb.. I have two egr solenoids closer to the front of the truck with only the one vacuum line going to the egr valve. Im really considering the duraspark but fearfull bout the annoying switch on the dash Id forget and burn my tranny. Not to mention it has to be dummy friendly so my Old Lady can drive it. And I just dont know if I have the knowhow. But Id like nothing more than to blow that emission crap straight to hell. Kill me...

 

[wildbill23c]

For now, disconnect the EGR wire, and the vacuum line, plug the vacuum line, and then try driving the truck. My 84 Bronco 2's EGR failed and if I hook it up as soon as the truck warms up it will die if I try to accelerate. I bet your EGR is bad.

 

[kimcrwbr1]

The engine will run ok in open loop on a cold start and run like ass when it goes into closed loop. There are five solenoids front to rear and your vacuum diagram should look similar to this without the top left switch.
http://www.therangerstation.com/tech_library/diagrams/1983vacuumhoseguide.jpg
TCP (blue) is the accelerator pump shut off valve on the front of the carb next to the fuel filter
DUMP (pink) is the air pump bypass thermactor the one on the bottom
Divert (black) is the thermactor switches air to the exhaust manifolds or to the CAT
EGR (green) opens the egr
the top one with the (orange) is the common problem and usually hooked up wrong. It is vented to filtered air from the top of the carb. Take a can of PB blaster and with the tube make sure all the vacuum lines are open and connected correct just leave the orange one disconnected at the carb and see if it gets vacuum pressure when you give it gas and let off the throttle. If so it is working correct, normally it will get plugged from blowby oil and dust from a poorly maintained air filter but some connect it to manifold vacuum and the first time you give it gas and let off the pedal the solenoid will open and open the egr fully. Others just plug it somewhere on the carb and does not let the egr close at an idle if it is not vented to ambient air. I fought it for a while and what I did was use the pressure of the PB blaster to clean all of the solenoids first. With the key on you should have power on the red wires to the solenoids. Just take a jumper to ground to energize the solenoids as you spray PB thru them. Then blast the small tubes clean and hook them up to their proper place. Disconnect the battery for 1/2 an hour and then see how she runs.

 

[CavScout0]

Thanks kimcrwbr1 for helping walk me through these problems. Well my vacuum diagram is slightly different. The orange hose is for the IAS solenoid. My diagram dosent have it going to the carb, I looked on the carb for a vacuum port other than for the TCP just to be safe but didnt find anything. It has it going to the a/cl dv. Im guessing its that little round thingy on my air intake snorkle with the vacuum port. Same idea it sucks in fresh filtered air? Well the hose wasnt plugged in where it was suppose to be it was hooked straight to the vacuum tree on manifold. Im guessing thats not good. Didnt have any more time to mess with it further due to the Devil I mean my wife hollering at me. Gonna clean the vacuum hoses and run the pblaster through the solenoids like ya said. Am I correct to think that the a/cl dv is that little thing on the air snorkle. And could that vacuum hose being hooked to the manifold vacuum tree cause a less than stelar preformance like Im having? Again thanks for all the help.

 

[kimcrwbr1]

I`m sorry I thought the 85 was the same as the 83-84 vacuum system. The a/cl dv is actually called a vacuum motor and opens the preheater tube from the exhaust schroud to put hot air in the carb during warm up then opens to the breather duct to the front of the radiator support. Can you clean the filter media on the egr bleed solenoid. Another common vacuum leak is the tube on the back of the egr spacer behind the carb. Trace the line from the carbon vapor cannister one goes to the bowl vent and the other from the solenoid to the egr spacer. It is center pointing back at the firewall on the egr spacer you should feel a slight vacuum at the cannister when the engine is running. Yea the a/cl dv can also be a direct vacuum leak if the diaphram is bad not uncommon. IDK maybe the computer is looking for the temp difference during warmup seeing how it tells the solenoid when to open the door to ambient air. One of those hand vacuum pumps works good for testing components for leaks. If you have the automatic transmission the vacuum to the modulator can also be a vacuum leak, replace any hard/cracked vacuum tubing.

 

[CavScout0]

Well after having starting issues I looked closer to my terminals, and grounds and such. I found my positive battery terminal where it connects to the starter relay rusted all to hell. My negative battery terminal where it connects to the block was rusted up too. I cleaned all that up. I found a 16 gauge fusible link on the starter relay semi melted looking as well. I ohmed it and came back ok. Inspected the starter and looked like the postive wire was slightly frayed and may have been touching the oil pan. Also I cannot find a ground coming off the starter. There has to be one for it to have started right? So Im going around and inspecting and cleaning grounds and connection. Is it possible the problems I am having could be electrical in nature. And can I ground the starter pretty much anywhere? Ohh and found the ground from firewall to back of block missing.

 

[kimcrwbr1]

Grounds are real important and could very well be the issue. The starter is grounded through the engine and tranny no ground is necessary. The computer has a ground pin #49 orange wire so go through and sand all the grounds you can find metal to metal. you can add a ground from battery pos to the radiator support if not there and for sure add the ground strap from the engine to the firewall. Bend wires and cables looking for weak spots. Pull all the electrical connectors apart and clean with electrical cleaner. add some dielectric grease when you put them back together and push all the pins in fully with a jewelers screwdriver from the back. That includes relays and the computer connector. Another good upgrade is add a ground from battery neg to the alternator housing. If it dont look right it aint and if you dont need to pass smog dont put any money into it just duraspark it and bring that engine to life.

 

[PetesPonies]

Ohms are nouns . . not verbs But otherwise, you are doing great If your block to firewall ground was missing, that is an important ground for sure. Make sure it is clean at both connections. I once had an engine that was turning the choke ( manual choke obviously ) cable fire engine red. The engine to frame ground looked good, but the cable was just sitting in the connector, no real connection. The choke cable, from carburetor to dash, was the only true ground. Kinda funny and dangerous at the same time. Good luck.