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Bronco II Ford Bronco II

Funky Problem

 
  #1  
Old 12-23-2006, 06:16 PM
Nightstalker
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Funky Problem

Anyone know where I can get a copy of the program that is loaded in the ECU of my 85 Bronco II??
I am having a problem that I can get to the bottom of. On cold wet days the vehicle goes around 10 miles and then it won't idle. When you let off the gas it dies. I can keep it running by playing with the throttle but the engine is obviously running wicked rich as you can smell raw fuel.
If I pull over and shut off the engine for several minutes and restart it the problem appears to be gone and does not return again until the next days start??
The engine fires just fine. ALl the ignition items have been replaced. I replaced all of the following items.'
Ignition coil, wires, rotor and cap, electric choke, throttle position sensor, EGR valve and position sensor, engine temp sensor, TSP control and solenoid, EGR valve control solenoids, oxygen sensor and several other items.
The ECU continues to show a code 31. The books I have tell me that that code idicate the EGR valve out of position during a recent engine operation. The signal getting back to the ECU isn't what would be expected but the EGR valve opens and closes fine and I placed a vacumn guage and hose out thru the hood so I could watch the amount of vac placed on the valve during engine operation and all that looks fine. I assume the ECU will make an adjustment for the signal being too low in the long run and store it as a variable.
The EGR not operating properly could explain the stalling condition but I have not really seen that the valve is the problem. I disconnected the vac line to the valve and ran the engine for several days. The engine performance was what I expected with the valve disconnected. The problem still appeared with valve disconnected??
Anyone that might have an idea on what is causing the problem please help.
The engine is a 2.8 with that notorious feedback carb, which to date has ran rather well??
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  #2  
Old 12-24-2006, 05:49 PM
93truck
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i had a problem like that on mine (87), found that the drivers side rear wheelwell rusted out and on cold wet days moisture was getting on computer causing the problem. good luck..
 
  #3  
Old 12-24-2006, 07:14 PM
D REECE
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u sound like u have put everything but a ecm. the egr wont make it run rich though it would make it run lean. its not possible it could be the choke pull off? "cold days" or voltage if it has it to the choke
 
  #4  
Old 12-25-2006, 11:01 AM
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After you replaced any parts, did you clear the codes? There is info on testing, retreiving codes, and clearing them here: http://www.therangerstation.com/tech_library/OBD_I.html
You may also want to check the tech info thread at the top of this forum, I forget what all info is in there. Once you've cleared the codes and you're still getting the same code, then you'll have to investigate further by testing the sensor(s) and wiring. Could possibly be a lemon sensor or a bad connection somewhere giving you grief. Also, if it's a moisture issue, you'll probably want to try and dry out everything and possibly track down where you're getting water into things. Dielectric grease and other easy-to-do fixes and preventions will save you a lot of headaches down the road. Also on therangerstation.com there is info on a Duraspark conversion as well as aftermarket intake / 2-bbl carb and even converting to fuel injection. You may have the notorious choke / flooding issue -- when was the carburetor last tuned up or rebuilt / replaced? Might also want to look into that as well.
 
  #5  
Old 12-25-2006, 12:00 PM
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Merry Christmas everyone!!
I went out and got another ECM aand replaced it thinking something might be funky in that. Problem still shows up. It is in under the dash and no leak problem getting to it at all. Vehicle body looks like new.

I cleared the codes after replacing each component but that code 31 still appears and like I said earlier if there was a real problem with the EGR system the problem should show up during other then thos cold days when the temp is below 40 and the air is damp.

Can you give me some more detail on that notorious choke flooding. I replaced the electric choke and rebuilt the carb as one of the first things done when the problem appeared. I have heard so much about how the feedback carb runs good until it gets on aways then it gives problems so I rebuilt it.
I set the choke pull off and the high rpm level for when the choke is closed. I can watch the choke open and it is getting what appers like a pulsed signal from the ECM which heats the coil in the choke. The signal pulses seem to get shorter and shorter then level out when the choke is open.

I have looked for water infiltration and have even replaced those rubber flaps around the fender cutouts so water won't get in but lets face it theres going to be moisture coming thru the radiator opening. I even placed a shield in from of the opening when the air horn gathers air for the carb. The exits in the front at the grill.

I will look the the info at ranger station and see if I can get any tips there. Next good day I will be out at it again.
 
  #6  
Old 12-25-2006, 12:38 PM
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Sounds like you may have an odd wiring or sensor issue, then. You may have to check for grounds and breaks in the wiring. If mechanically the EGR valve is operating as it should, then somewhere electrically there is something askew. I would pull the looms apart and check each wire going to the EGR position sensor as well as the connector(s), etc. inch-by-inch to see if there is a break or bad connection. If there are no shorts to ground that are not supposed to be there and all of the wiring and sensor(s) check(s) out, then I'm at a loss. Good luck, and hope you get it fixed!
 
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Old 12-25-2006, 12:53 PM
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Thanks
What exactly does the 31 code really mean on the engine??
When I check the resistance on the sensor it is out of range.
I thought that maybe the EGR valve was not seating so I removed it. It looked fine. I cleaned the port and the valve itself and got the same readings. While trying to remove the 3 nuts holding the sensor in place one of the snapped the stud off. After getting the sensor off I read it in its out of unit state. It worked fine and as I moved it back and forth the readings smoothly changed with it. I connected it back in its socket and pulled the ecm. I read the wires going to the unit and did not see any problem. While it was connected I read the readings by moving the sensor. I got the same readings that I received with the unit on the bench. I went out and bought a new EGR valve and sensor. I get the same darn readings from the new one. The book states what the range should be. Mine is a little off that reading but I know what they say in the manuals really isn't always whats in the world. I went to the junk yard (buddy owns the yard) and went to a few vehicles with the same engine. The readings on those were similar. Hence i disregarded that the EGR is the problem but I still have the code. I can make th ecode disappear by leaving the sensor off the vlave and changing its value. Being a very inventive person I was going to have one of my friends in the machine shop at work make me a tight fitting sleeve that I could place in the pin on the sensor. I would keep adjust the fit to get the readings within the range in the book which would clear the code. One thing I am positive on is the EGR is fully closed when no vac is on the line and it fully open when full vac is on the line.
 
  #8  
Old 12-25-2006, 01:02 PM
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Then there is an issue with the valve-to-sensor fit or the sensor is faulty. "New" doesn't necessarily mean good. If the specs are not the same as what the manuals dictate, then the sensor is bad and will throw a code. Sounds like you're closer to resolving the issue, though!
 
  #9  
Old 12-28-2006, 09:17 PM
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Another day in futility!!
I spent most of today working on the problem. The only code the ECM is posting again is the 31 code. I pulled apart the wiring harnes and follwed the wores back to the ecm. I didn't find any troubles with the wiring. Checks with a meter, no opens, no shorts to ground. I place the sensor back in a back pinned the wire at the ECM. The signal getting back to the ecm looks fine. I went out and got another sensor and I get the same readings on that sensor as I got on the older one. I also have another EGR valve and connected that so I could run the see if there is a fit problem on the sensor. It looks fine. I manipulated the sensor to change the position of it. I ran the test with the sensor in all different settings and still get the 31 code???
I can see the signal change at pin 27 which is the signal back to the ECM as I change the setting.
Could it be that code 31 does not have anything to do with the EGR system on this vehicle?? In one of my manuals code 31 (on trucks only) can be "the EVAP signal is below minumum voltage" ??
Will look at things in that area tomorrow. I tested the canp and the evap solenoid and both of those work fine.
Because the problem occurs on days the temp is below like 35 I changed the temp sensor ECT just to be on the safe side. No change in results?
One of the last items in the tech manual says if all else fails change the ECM. It did that today too and still get the code 31.
I am sure if I can kill this code problem the idle problem will go away?

The control item that drives the dash light is unplugged. Its not one of those that can be reset. Does leaving this unplugged cause any problems. I believe it is called the "inferred mileage sensor" and its shown on the wiring diagram as such.
 
  #10  
Old 12-30-2006, 02:00 PM
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I looked at the solenoids for the canp and evap more extensively today. The Evap solenoid though looking Ok had a problem in it not allowing it to open. I got another one and replaced it. Everything in that system now checks out fine. I am still getting the code 31.
A friend brought overhis manual. When we looked at the code 31 there was a detail in brackets on the code that said that this code can be generated by some truck applications an not be an abnormal condition that would cause driveability problems???
Anyone heard of this??
If I knew what the computer is doing with the information on the feedback sensor that would be helpful. Everyone knows it tells the computer the position of the EGR valve based against an expected position depending on other engine readings. Its the detail on how it uses that information, other conditions its looking for at the time etc. that I am looking for.
 
  #11  
Old 12-30-2006, 02:13 PM
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You may want to pick up a copy of the Chilton's (?) Emissions book as well as the Chilton's and Haynes manuals for your rig and see if you can find info that way. Something still tells me there is some sort of underlying problem with the sensor readings that should be investigated further, otherwise, you'll still get an out-of-range code (which I have had no issues that I know of with this).
 
  #12  
Old 12-31-2006, 07:08 PM
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I have each of those manuals.
I am at wits end on this problem.

I was looking at the vac conections today to be sure there are no cracks etc. on any of the lines. Looking at the connection diagram it shows the canp connection above the throttle plates if that is what the "upside down t" means on the diagram. Usually vac connections are shown as a "t" on a diagram meaning the connection is below the throttle plates or the "upside down t" meaning the connection is above the throttle plates. My canp vent is below the throttle plates. It has always been connected to that spot on the intake. The choke pull off is connected to a vac connection above the throttle plates. Could these two be connected in the wrong place?? My thoughts are that when the canp is signalled to vent the intake vac is stronger then the spring closing pressure on the solenoid allowing it to stay open until the engine is shut off???
Just a thought??

I did more checks on the EGR position sensor as well. The sensor reads 4K ohms, the book says it shoud be at 5500 ohms. At its bottom position it reads 59 ohms, the book says it should be at 0 ohms. I have two other sensors and both of then are off as well. It may be that the sensors are not any good. They all read 4000 ohms as their high reading. One of the manuals says that code 31 one means the egr sensor is reading above 4% of the reference voltage which is 5 volts. Doing the math 59 ohms will produce a reading higher then the 4%.
I took a simple potentiometer and made a simple tester to test the signal send back to the ecm. Using 0 ohms the voltage reading sent back to the ecm was 0 volts. Figured this would kill the 31 code at least for the test which would have me out looking for another sensor that reads below the 59 ohms.
Still getting the 31 code.
 
  #13  
Old 12-31-2006, 08:00 PM
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Did you do all of the code readings... i.e., in order, KOEO (first!), KOER, etc. Something tells me maybe you didn't clear the memory. 0 ohms going back to the ECM... wouldn't that give you 100% or close to it of full 5V? Or is my line of thinking wrong? I'm thinking it's a combination of sensor / wiring personally, but without physically looking at everything, I can only give my best guesses. As far as the vacuum line routing goes, if you have a 100% bonafide vacuum line diagram for your specific engine / vehicle, I would route / check the routing of all of your vacuum lines according to the diagram. Sometimes if one line is connected here instead of there, so to speak, something may not work right. It's a possibility. Don't let it get you down, keep pluggin' away at it!
 
  #14  
Old 01-06-2007, 12:35 PM
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Back to another work week!!
I have the operating of the vehicle down to a science now. I start it and run till I see the temp guage on the dash move. I shut the engine down for 20 seconds or so and take off. The problem does not appear at all.
After a conversation with a Ford tech. I was told that if the computer generates a code 21 on a cold engine the ECT sensor is bad regardless of the test readings on it. It puts the engine in limp home mode as that sensed reading is one of the critical readings the computer scans for at startup. When the engine is restarted the temp on the engine is up and the new scan sees a temp the conputer can work with and the engine goes into normal operation??
Does this sound logical??
After work last night I changed out the ECT, for the minimal cost and the few minutes to do this change I gave it a shot. Will do a normal start and take off in the next few days to see if that has changed the engine operation. I tested the sensor I removed and it still looks fine???

Do you have any information on the electronic relay that drives the choke heater?? The signal getting to the chock is a pulsed signal. I assume that this little device can not handle voltae to it all the time so the unit pulses the signal eventually warming the device?? It must get to some point where it sends a pulse the keeps it warm?? I can't find any information on it anywhere.
The plastic on the original one disintigrated letting water into it. I could not find a new one anywhere. I went to the junk yard and got one out onf a Ford F-150, pins looked the same and it plugged right in. Just want to be sure that unit is the same temp and does the same thing. It could have some thing in it that sets the choke differently after restart that could be affecting my running problem.
 
  #15  
Old 01-06-2007, 05:20 PM
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Did the 2.8s have a heated choke or a choke pull-off solenoid / idle soleniod... ? I can't remember. I'd have to look it up, but I don't think those two parts are different, but it could be a possibility. I'm wondering if this is part of my cold start-up issue on my FI 2.9. Usually, I can start up, it'll die within a few seconds (symptom of IAC problem), then I can start it back up, run it until it's warm, shut down, then on the 3rd start up, I have no issues, other than a slight misfire / rough idle (which I'm suspecting both valvetrain and maybe uneven spark plug gaps to be culprit, but it doesn't affect much). You may or may not have issues with the right pulsed signal getting to your choke heater, or the choke heater / bi-metalic spring itself could be hosed due to the water issue you mentioned. You may end up having to replace the choke itself or get a rebuild kit or a rebuilt carb... but I would probably opt for just going out and spend the extra time in the mornings fiddly dinkin' with it and warming it up, etc. before going anywhere until it completely craps out. *shrug* OH, and I just looked it up, and yes, the choke thermostat and pull-off are identical for both F150 and the BII ... and now wondering if the thermostat part is faulty... something else to look at and check
 

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