my check engine light was on constantly so i did the self test and came up with code 31. this was thru the KOEO (key on engine off) test. I pulled the EVP sensor (EGR position sensor) and found the tip to be worn and cruddy with carbon. I thought it was obvious so i just replaced the EVP sensor. Now i am still getting the code 31. I left the battery disconnected overnight and also erased the codes during the test and am still getting code 31. I just did a KOER (Key on engine running) test and got a code 11 which means system check OK. I am now stumped. Anyone have any suggestions on how to cure this problem?
Any help is greatly appreciated.

thanks,

Rusty

 

Rusty , Whats the Model yr , engine etc ?

 

>Rusty , Whats the Model yr , engine etc ?

sorry, It's a 1988 f250 lariat 4x4 5.8L c-6. oh and i replaced the EGR pipe and valve a year or so ago.

thanks,

 

Rusty9, my code reader book (Innova, Fountain Valley, CA) states that for V-8 trucks Code 31 is "EVAP Control System below minimum voltage." My '90 Bronco threw the same code. Disconnecting the EVAP hose to the throttle body and capping its inlet on the throttle body made absolutely no difference in driveablity. Unplugging the EVAP solenoid's electrical connection and loosening the gas cap in case its vent was plugged made no difference either. I am wondering if my book is in error, and should read "EGR Control" or "EVP" or "EVR"?

In any event, I would be worried about my EGR valve if the EFP was carboned up. It's supposed to be clean if your EGR is sealing properly. Good luck.

John

 

>Rusty9, my code reader book (Innova, Fountain Valley, CA)
>states that for V-8 trucks Code 31 is "EVAP Control System
>below minimum voltage." My '90 Bronco threw the same code.
>Disconnecting the EVAP hose to the throttle body and capping
>its inlet on the throttle body made absolutely no difference
>in driveablity. Unplugging the EVAP solenoid's electrical
>connection and loosening the gas cap in case its vent was
>plugged made no difference either. I am wondering if my
>book is in error, and should read "EGR Control" or "EVP" or
>"EVR"?
>
>In any event, I would be worried about my EGR valve if the
>EFP was carboned up. It's supposed to be clean if your EGR
>is sealing properly. Good luck.
>
>John
>

Well the old EVP sensor had a burnt tip with a very small amount of carbon. the EGR valve is pretty new. i figured that if the tip was worn it would cause it to not read properly and hence the code 31. Now I don't know what to check or how to troubleshoot the system. What does the gas cap have to do with code 31? will it really cause the check engine to stay on? Is there some kind of test i can do to isolate the problem?

thanks for the help.

Rusty

 

Rusty , Make sure the Egr valve is closing completely . Is the Evp Gray or Black ?

 

>Rusty , Make sure the Egr valve is closing completely . Is
>the Evp Gray or Black ?

well it is a cream color actually but i am pretty sure that is the "grey" one. The EGR and EGR-pipe are pretty new but i guess the valve could have gone already. how do i see if it is closing completely? By the way i should mention that the truck will stall at times; like coming to a fast stop. it lugs a bit at idle and there is some hesitation/flat spot at take off. I haven't cleaned the intake & throttle plates in a while though - that might have something to do with it.
I will look into my little haynes manual to see if there is some procedure to do.

thanks again

cheers,

 

There are different test readings for the different color Evp sensors . If you have some off idle stumble it may be that the egr valve is not closing or opening when it shouldnt , this would cause the Evp code . Visual inpsection is about the only way to confirm its opening & closing properly . It really doesnt take a lot of carbon to stick it open .

 

I had been having the same problem, changed the EGr Valve Position sensor, turned out to be that the green hose that is on the EGR valve was shot, replaced it and it cleared the cade 31

 

O.K. guys, i will check those things out tomorrow. let you know how it goes. thanks.

Rusty

 

>I had been having the same problem, changed the EGr Valve
>Position sensor, turned out to be that the green hose that
>is on the EGR valve was shot, replaced it and it cleared the
>cade 31

hey fshorey. i checked that green hose that goes to the EGR and gave a little tug to see where it went to and it snapped right in half. it was totally brittle. tried to pull off the other end at the "EVR valve" and it broke there too. there is also a black hose like the green one that comes off the EVR valve as well and i was wondering if i should replace that too. are they vacuum lines? the green one had no vacuum hardly at all when i pulled it off the egr valve when running. should it have had a strong vacuum? anyway, i think the stores are closed today. did the green hose cost you much and is it a dealer-only item. i hope this solves the problem.

i had a look at the EGR valve itself. it is still shiney new inside and out but i cannot see much to tell if it works or not. again it is pretty new so i have some confidence in it. i will replace the green line/hose and see what happens. keep ya posted.

thanks.

any other words of wisdom?

 

o.k. me again. i just replaced the entire green vacuum hose that goes from the EGR to the EVR. nothing changed. i am assuming now that my EVR (EGR Vacuum Regulator)needs replacing. But before i spend another 70 bucks does anyone have any other ideas. there doesn't seem to be any vacuum coming through the line to the EGR. As the line comes from the EVR i assume the EVR is fried. follow?

cheers,

 

Rusty9, are you checking for vacuum from the EVR while driving? I know my trouble doesn't really start until I reach a certain temperature & speed. I don't know what parameters guide the EEC inputs to the EVR, so that's the only way I can think of to check out the EVR function. Since the EGR will be closed, I'd think the EVP would be sending position data that should make the EEC want to keep trying to open the EGR. If so, and if the EVR is working, you should get a reading as you drive along. Heck, tee the vacuum gauge into the green line and you should get a real good picture of what's going on. That would let you leave the EGR hooked up and make for a valid test condition. The procedures in the Haynes aren't good enough to rely on--a new EVR tests about the same as an old, suspect one. Good luck.

John

 

[updated:LAST EDITED ON 05-Apr-02 AT 01:33 PM (EST)]>Rusty9, are you checking for vacuum from the EVR while
>driving? I know my trouble doesn't really start until I
>reach a certain temperature & speed. I don't know what
>parameters guide the EEC inputs to the EVR, so that's the
>only way I can think of to check out the EVR function.
>Since the EGR will be closed, I'd think the EVP would be
>sending position data that should make the EEC want to keep
>trying to open the EGR. If so, and if the EVR is working,
>you should get a reading as you drive along. Heck, tee the
>vacuum gauge into the green line and you should get a real
>good picture of what's going on. That would let you leave
>the EGR hooked up and make for a valid test condition. The
>procedures in the Haynes aren't good enough to rely on--a
>new EVR tests about the same as an old, suspect one. Good
>luck.
>
>John


Thanks for the input John as well as the rest of you. here is the latest in this saga. i went to library to do some research. this is what i found out. There are 4 different types of EGR systems for ford. Mine is the ELECTRONIC EGR or a EEGR. it is run by vacuum from the EVR (EGR regulator) but is different from some other Ford EGR systems in that the EGR valve is not serviceable. This is why i was confuesed about how to "clean" the EGR out like some have recommended here. there is no way to remove it except to unscrew it from the large exhaust tube that goes to the manifold/exhaust. I broke the tube off at the top last time i replaced the EGR. I am scared to try this again as it is an expensive lesson. the EGR seizes on to this Tube cause of heat and is very difficult to remove. besides there is nothing that can really be done with it cause it is one piece and cannot be taken apart. you can take the sensor off the top though and i have done that. SO the EGR and sensor on top are new. I replaced the "green" hard plastic vacuum line to the EVR. I also learned that there should be NO vacuum to the EGR at idle (and i do not have any). I brought the engine to WOT (wide open throttle) and there was still no vacuum at the EGR - i do not know if this is right. Should there be vacuum at WOT? If there is supposed to be vacuum at WOT then i would assume that the EVR (EGR regulator) is fried but i do not want to spend $79 on a new regulator if this is not the problem. I do not have a vacuum tester - just my finger. i still have the code 31 and the CHUCK ENGINE light is still on constantly. I need some more advice/recommendations. I am not any good at testing things with a voltmeter - have never done this and find them a bit of a mystery. any tips on how to test things with a voltmeter? i guess i have to go buy a vacuum tester eh? how can test while driving? run a long tube out the window?

thanks alot guys,

Rusty,

 

Nobody has come on board yet with factory service manual test procedures for the EVR. Absent same, I wouldn't rely on anything but the driving test.

Quote: "i guess i have to go buy a vacuum tester eh? how can test while driving? run a long tube out the window?"

Exactly. That's the only cheap, sure way I can think of to check out your EVR.

Quote: "I am not any good at testing things with a voltmeter - have never done this and find them a bit of a mystery. any tips on how to test things with a voltmeter?"

You want a volt-ohm meter or a multimeter. Make sure it comes with an instruction manual. A set of small alligator clip ends would be nice, but not essential--you can get alligator clip ends at Radio Shack and/or jumper wires with clips already attached. The meter's black negative lead usually plugs into the hole marked "common", "negative", or "-"; the red positive lead plugs into the hole marked "Volt-Ohm-Amp" or something similar. You use different dial settings to test for different values. Almost all modern automotive systems are 12-volt direct current with a negative ground, so all voltages will be read off a hot (energized) terminal with the meter on the direct current settings. Resistance is measured in ohms, sometimes expressed as the Greek letter omega. The circuit thru which you are measuring resistance MUST NOT be hot or you will burn out a diode/fuse/breaker in your meter. So you usually test for voltage before checking resistance. Amperage is tougher, and you usually need a more expensive multmeter to check anything but very minute amperage, so it's probably best in the beginning not to try testing for amperage. Or you could rig yourself up an amperage tester from one of those amp gauges that hangs below a dashboard. Good luck.

John