All:

Tonight I performed a smoke test in order to find a possible vacuum leak on my 1986 F-150 (5.0 EFI). I have been having some rough idles, some harder shifts (I have an AOD transmission) and the occasional stall at a red light.
This past weekend I replaced the EGR and the sensor on top disconnected the negative battery cable for an hour or so. I then drove it, came back and pull codes - 31C and an 18O came back. The new EGR really made no real difference that I could tell in the idle.

Back to the vacuum test.

I took off the break booster vacuum line at the vacuum tree and installed a hose and that is where the smoke entered. My son and I watched for smoke in the lines, seals, etc. The only place that smoke appeared was the charcoal canister. It appeared to be coming from the "front" hose. (The rubber mount below the hose does feel crusty to the touch). I will try to upload a video of the canister and the smoke coming from it.

Could that really cause any symptoms of the rough idle? I can't think so - but what do I know? I assume that I should replace the hoses into the canister or maybe the canister itself but I have read here in the forums that they rarely, if ever, fail or are prone to problems.

Any insights are appreciated.

 

Back to the code test.

The codes are 2 digits. 31C and 180? What are you referring to?

 

Code 31 is still an EGR code. Your EGR is still not correct. Did you get the code during a KOEO test or during a KOER test?

If you scan the codes with the key on engine off, and you get a code 31, that means the computer got a voltage signal from the sensor on top of the EGR lower that it was expecting. When the engine is off, key is on, and the computer is looking at the sensor, it needs to see at least .2v dc from the sensor.

If you are getting the code 31 during the key on engine off and also the key on engine running, the guy in the book says to unplug the plug to the EGR sensor, and put a jumper in it and run the codes again and you should get a code 35. Unplug it and put a jumper between the vref wire (orange/white) and the signal wire (brown/lightgreen). This should put 5v dc on the signal wire and that is a voltage higher than expected, and it should generate a code 35. He says this will prove the wiring, connections, and the computer are good.

If you never get a code 35, this verifies you have a wiring problem, a connection problem or a bad computer.

 

Gents,

I pulled the codes doing the key on-engine off test. I read somewhere that I should take care of the codes in this mode before performing the key-on-engine-running test. Maybe I am wrong about that. (I should have told you that first).

Franklin2 - So now I figure that I jumped the gun in buying the new EGR and sensor. Crap. Oh well. I will do what you instruct and test the voltage and report back.

For my information - what happens if it is verified that I have a wiring problem? I will have to rely on you all to guide me through this. Hopefully, with my limited skills I can fix this in my garage.
Do you think that this EGR problem is the source of my issues? Maybe the smoke coming out of the charcoal canister is not the main problem? I just thought that I had better check for a vacuum leak.

(In a perfect world there would be a "Rent a Mechanic" who would come to my garage. I would have a cold six pack there for him and he would watch me work on the truck advising me to "do this" or "no, don't do that".


But I learn as I go.

I will report back soon and await your instructions/impressions.

 

Update:

So this weekend I ran the KOER test as Franklin2 recommended. I kept the EGR sensor plugged in this time because I wanted to see if it would throw the 31R code when running.

I warmed the truck up first and then put on the OBD1 code reader. I got my codes and the 31R code disappeared. I was pleasantly surprised but figured that maybe there was an error on my part. So shut the truck off, waited a minute or two, and I ran the test immediately again. Again no 31R code. With no 31R code during the KOER test I figured that I did not need to run the test again with the EGR sensor off. Could it be that the problem is solved? Maybe the EECIV somehow fixed this internally? If so, I am very happy.

I still think that I have a vacuum leak somewhere because when I start the truck the engine idle is high (I do not press the gas pedal before turning the key). This high idle will stay for a couple of minutes before it settles down to the normal idle. I can tap the gas pedal and it will go down to a normal idle if I am driving somewhere. I figure that I will do another smoke test to see if I can find the leak.

That's the latest.

 

It is supposed to high idle on cold starts. Sounds like everything is working normally. The computer simulates the high idle that you would have with a choke on a carbed engine. The high idle overcomes the resistance of the cold oil, helps the fuel stay atomized as it enters the cylinder on a cold engine, and helps the battery recover with the alternator spinning faster. It's also helps the engine heat up faster, which is good for emissions. It's just the way most engines are programmed.

 

What is this Code thing you are talking about?