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Old 01-18-2003, 08:52 PM   #1
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Code 34 - EVP voltage above closed limit

I just ran KOEO and got Code 34. What can I do to fix this problem? I did a search and found what the voltages should range from, but I dont if you can adjust the voltage like the TPS. I know EVP stands for EGR Valve Position Sensor, but I am not sure how to adjust the voltage. I already cleaned the EGR valve since it was sticking (no longer get CE light) but I still get this code 34. Thanks.
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1989 5.0 LX Hatch, 5spd, 3.55, Bullitt susp, 5 lug disc conv, Bassani cat X pipe, 427K miles on original longblock.
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Old 01-18-2003, 09:41 PM   #2
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are you certain the valve is closing all the way? a way you can test this is to pour gasoline into the hole with the pintle closed, and see if it leaks past the pintle. that'll tell you if it is closing all the way, no leak should be present. If it is indeed sealing, you probably need a new EVP sensor if the code is still present.
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Old 01-18-2003, 11:18 PM   #3
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Yes the valve is closing all of the way. I just bought a new EGR PS at Autozone for $17. I disconnected the battery and put the new one one (took about 15 minutes) and then reconnected the battery. I am still getting the same code 34. Any suggestions?
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1989 5.0 LX Hatch, 5spd, 3.55, Bullitt susp, 5 lug disc conv, Bassani cat X pipe, 427K miles on original longblock.
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Old 01-18-2003, 11:40 PM   #4
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probe the wires coming off of it....it is just like a tps. one will be 5v, probe the other two.

mine shows ~.4v while closed, and 4.3v if I open it all the way by appying a strong vacuum (human being can apply ~24in HG).

it is a real pain in the ass to get at the wires to do the probe.

did you mean that the EGR vavle is new?
could you try the gasoline thing just to be sure?

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Old 01-19-2003, 01:02 AM   #5
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I poured carb cleaner into the hole where the pintle is closed. The cleaner did not leak down past the pintle. I soaked the EGR valve and scraped as much as I could for the past 2 hrs. Bolted it back up again and still have code 34. I did run the KOER tests and everything with that was fine except for the code 34. Even the engine balance test came out to be 90. Not bad for a 200K mile motor.



I am about to give up on this EGR crap. I think I will just rip out everything and go buy brand new stuff again!!!!
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1989 5.0 LX Hatch, 5spd, 3.55, Bullitt susp, 5 lug disc conv, Bassani cat X pipe, 427K miles on original longblock.
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Old 01-19-2003, 05:12 AM   #6
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did you probe the wires?

is the EVP sensor new?
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Old 01-19-2003, 10:22 AM   #7
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Yes, the EVP sensor is new. Where do I probe the wires at and what voltage should I look for? Do I disconnect the harness from the sensor and test the voltage difference between the 3 prongs? Thanks again.
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1989 5.0 LX Hatch, 5spd, 3.55, Bullitt susp, 5 lug disc conv, Bassani cat X pipe, 427K miles on original longblock.
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Old 01-19-2003, 10:44 AM   #8
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Quote:
Originally posted by MinionII
probe the wires coming off of it....it is just like a tps. one will be 5v, probe the other two.

mine shows ~.4v while closed, and 4.3v if I open it all the way by appying a strong vacuum (human being can apply ~24in HG).

it is a real pain in the ass to get at the wires to do the probe...

I used pins, not tacks, sharp pins to pierce the wires on the harness that connects to the EVP sensor. As I said, one of the wires will be 5v reference wire.
To find this wire, conect the negative lead of your voltmeter to the neg batt terminal, and connect the positive lead to the pins, one at a time, that you connected to the EVP sensor harness. Once you figure out which one is the 5v ref wire, you want to probe the other two wires, hooking the positive lead of the volt meter to one, and the negative to the other.
My car gives ~.4v, with the EGR valve fully closed.
You need to do all this with the key in the on position.

good luck
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Old 01-19-2003, 10:55 AM   #9
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OK, of the 3 wires, I found one that gives 5V. I connected the positive to the 5 volt wire and tested the others. One wire gave a reading of 5 volts and the other gave 3.7 volts. Again, these are the wires that plug into the bottom of the sensor. And yes, KOEO.
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1989 5.0 LX Hatch, 5spd, 3.55, Bullitt susp, 5 lug disc conv, Bassani cat X pipe, 427K miles on original longblock.
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Old 01-19-2003, 11:25 AM   #10
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I'm pretty bad at explaining stuff, but what you want to do is eliminate the 5v wire. I don't mean take it out, I mean identify which one is 5v and ignore it. It is the other two wires that you want to get a reading from.

put a pin in each of the other two wires and hook the volt meter to them, neg on one wire, pos on the other. Now see what kind of read you get....

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Old 01-19-2003, 01:43 PM   #11
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OK, thanks. I redid it and got .96volts KOEO and when I turned the car on at WOT I got 5 volts while testing the same wires. Hmm, it seems to me that the .96V when closed is too high and thats why I get the code 34. It could be that the sensors pin is being depressed too much because the EGR valve is sticking a little more open than it should be. I have both a new EGR valve and EGR PS, but maybe a second set will do the trick. Thanks again MinionII!!!
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1989 5.0 LX Hatch, 5spd, 3.55, Bullitt susp, 5 lug disc conv, Bassani cat X pipe, 427K miles on original longblock.
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Old 01-19-2003, 08:45 PM   #12
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Had the same problem a while back. Got a 34 code and changed the EVP and EVR sensors. Still got a 34 code. At the advice of another Corraler, I changed the EGR itself (the expensive part) and the code 34 went away. Even though the old EGR was working.

Just a suggestion and LOL.
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Old 01-19-2003, 11:27 PM   #13
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Don't forget there is another vacuum gating valve that operates the EGR assembly. It is under the control of the computer. It has a filter under a cap that may be dirty by now. That filter is there to filter incoming air for the release function of the EGR. If air cannot enter the EGR diaphram, it won't release once opened by vacuum. The EGR operates around 2200 rpm. The computer opens the valve to let engine vacuum go to the EGR for operation. The sensor on the top of the EGR reports back to the computer wether it operated or not. The vacuum level, at operation, will be around 5 inches of vacuum.
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Old 01-20-2003, 12:24 AM   #14
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Thanks again. I will triple check everything again.
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1989 5.0 LX Hatch, 5spd, 3.55, Bullitt susp, 5 lug disc conv, Bassani cat X pipe, 427K miles on original longblock.
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Old 01-20-2003, 12:34 AM   #15
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if your getting that code 34 in the first set of codes (the KOEO codes) it won't be caused by a dirty EGR solenoid filter...that would show up under C (continueous).

The first set of codes scans all the sensors in there current state, whereas the continueous shows problems that happend while the car was running.

My reading across the wires (not the 5v ref wire) is ~.4v when closed, yours was ~.9. I pretty certain that's your problem. If your certain the EGR valve is sealing, maybe you can modify the EVP sensor? (Never took that apart) Or just take it back and swap it for a good one.
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Old 02-28-2004, 11:38 PM   #16
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I've had a code 34 on my 91 5.0 for about 3 years now. I found some more troubleshooting info here:

www.kemparts.com/TechTalk/tt12.asp

It seems there are two different types of EVP sensors, one light colored and one black. My car came with the light colored one, which agrees with the 0.4V at KOEO. I replaced the EVP about 3 years ago and I still had the code 34. I certainly don't want to go out and buy an EGR valve and still throw the code 34. I suspect my EVP is out of calibration.

Maybe I'll troubleshoot some more tomorrow by backprobing the EVP under KOEO conditions while applying vacuum to the EGR.

My EVR valve coil reads around 44 Ohms, which should be good. If I remove the filter from the EVR and block off the vacuum bleed orifice, the engine will stall due to the EGR opening. I assume this means my EVR is good. I will probably check the EVR voltage as well.
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Old 02-29-2004, 12:38 AM   #17
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The other part of all this is; is the vacuum valve that gates manifold vacuum to the EGR working? Your only looking at half the operation by working on the EGR and EVP.
The computer operates this valve under cruise conditions and gates about 3 to 5 inches of vacuum to the EGR, then the EVP reports this operation back to the computer as a check that the operation was completed. It's when the EVP does not operate, that failure is detected no matter for what reason. It is the end-all test that the total system has operated sucessfully.
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Old 02-29-2004, 02:42 AM   #18
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Quote:
Originally posted by Bluegrass
The other part of all this is; is the vacuum valve that gates manifold vacuum to the EGR working? Your only looking at half the operation by working on the EGR and EVP.
The computer operates this valve under cruise conditions and gates about 3 to 5 inches of vacuum to the EGR, then the EVP reports this operation back to the computer as a check that the operation was completed. It's when the EVP does not operate, that failure is detected no matter for what reason. It is the end-all test that the total system has operated sucessfully.
The vacuum valve is the EVR I mentioned. I had one fail on me a few years back. The coil was open.
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Old 02-29-2004, 03:15 AM   #19
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You did install the O-ring that seals the EVP to the EGR valve, right?

If so, I'd exchange the EVP first since it is new. I've been burned before by new stuff that seems to cause the same problem I was trying to fix.

If that doesn't get it and you're absolutely positive the EGR valve is not sticking or otherwise being held open a bit when it is installed (incorrect gasket, carbon, etc.) then you could grind a bit off the end of the EVP sensor shaft to bring installed voltage down to the .4 range.
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Old 02-29-2004, 09:21 PM   #20
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Well, I backprobed the EVP sensor and sure enough, I was getting somewhere around 1.13VDC at KOEO. I also noticed that the EGR was sticking when I applied vacuum. I replaced both the EGR valve and the EVP sensor ($114.00 at AutoZone) and voila, code 34 is no more.

After the new EVP and EGR valve was in place, KOEO EVP voltage was around 0.56VDC.

Thanks for the inspiration! I had that fault code for a long time. Maybe my fuel economy will pick up a little.

If I just hadn't been so cheap, I could have had this problem fixed a long time ago.
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