EVP code and buzzing
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EVP code and buzzing
I can't get code 34 cleared from the self-test process. I have recently replaced the EGR valve and EVP sensor which knocked out a few, but I'm still getting the "EVP above the closed limit of .67V" code.
I checked out all the voltometer tests given in Haynes on the EVP. Only one failed: the reading for stray voltage at the PCM (Pin 27) read .9mV instead of zero. I took this as not being a problem, but please correct me if I'm wrong.
I don't know if this has anything to do with the code, but....
Yesterday I replaced a bunch of vacuum hoses and the PCV valve, after which a buzzing noise started comming from in front of the fire wall. The buzzing noise sounds to me like the PCV valve opening and closing repeatedly. The buzzing intensifies with higher RPM and slowly drops off when comming to a stop. (Does that mean it has to do with vaccum?)
I apologize for the long post, but I was hoping to be descriptive enough for everyone. If anyone could give me any advice on fixing either problem, or maybe even relating the two, I'd greatly appreciate it.
Thanks,
Kyle
I checked out all the voltometer tests given in Haynes on the EVP. Only one failed: the reading for stray voltage at the PCM (Pin 27) read .9mV instead of zero. I took this as not being a problem, but please correct me if I'm wrong.
I don't know if this has anything to do with the code, but....
Yesterday I replaced a bunch of vacuum hoses and the PCV valve, after which a buzzing noise started comming from in front of the fire wall. The buzzing noise sounds to me like the PCV valve opening and closing repeatedly. The buzzing intensifies with higher RPM and slowly drops off when comming to a stop. (Does that mean it has to do with vaccum?)
I apologize for the long post, but I was hoping to be descriptive enough for everyone. If anyone could give me any advice on fixing either problem, or maybe even relating the two, I'd greatly appreciate it.
Thanks,
Kyle
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From: Derbyshire, UK.
Sounds like you still have a vacuum problem. Have you tested the lines with a pump & gauge? You might still have a leak somewhere that is causing a loss of vacuum in the whole system. For the PCV system to work properly you need to check the 3/4" stiff hose that runs from the back of the airbox to the oil filler neck is clear as it will suck air in through this, through the crank case and then through the PCV valve to the Plenum. Sometimes they get blocked with emulsified oil. Also check the filter in the lower half of the airbox.
Also you can test the PCV valve by carefully pulling it out of the valve cover when the motor is running and seeing if you have a vacuum on the end (a finger makes a good test probe).
Test each vacuum circuit with a pump and gauge from the 'tree' on the top of the plenum to see if one is leaking.
Also you can test the PCV valve by carefully pulling it out of the valve cover when the motor is running and seeing if you have a vacuum on the end (a finger makes a good test probe).
Test each vacuum circuit with a pump and gauge from the 'tree' on the top of the plenum to see if one is leaking.
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I already tried disconnecting the air hose from the air box, but that didn't produce any results. I doubt it's clogged b/c I installed a new engine and cleaned the hose less than 3k miles ago. I guess it's time to go buy a vacuum gauge huh?
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If you are certain the EGR valve is not binding and not restricted in its travel, try cleaning the EVP filter in the top of the EVP sensor. Retest. If it returns, test the resistance of the EVP sensor. Its should read no less than 100 ohms with the EGR valve wide open (vacuum applied). If the reading is less than 100 ohms, the EVP sensor is bad. If the signal return voltage from the EVP sensor is higher than 4.81 VDC the Code 35 will be generated rather than Code 34. Code 35 is indicative of a bad EVP sensor or a faulty ECA (main computer).
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Well, unless I got faulty parts, the EVP sensor can't be at fault. I just replaced the EGR valve and the EVP sensor (new, not reman.) less than 100 miles ago. I'll get a vacuum gauge, test further, and post again then. Thanks for your help.
Lead Driver
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From: Gateway to the West
Poor connections could be the issue as well. There are only a handfull of things that can generate Code 34 and if the EGR valve and the EVP sensor are NOT at fault, its got to be in the wiring. IS Code 34 the ONLY code still rearing its ugly head?
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Yeah, Codes 65 and 77 are related to things that were not done during the KOER test. Namely the OD switch not being disengaged and engaged and the "goose" test not being performed during the KOER test.
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Something I just thought of in regards to the "buzzing" noise. If your PCV valve was allowing oil through at any point in the past, the oil could have weakened the rubber hose running from it to the barb on the upper intake plenum. The negative pressure created by vacuum passing through the weakened hose can cause it to collapse and generate a kind of vibration or "buzzing".
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I'm still getting that 34 code, but the truck is running really well.
Yes, correct grey. It was the PCV valve buzzing for sure. I just replaced the PCV 30 miles ago, but I pulled it out again to check it, and there was oil on the bottom again. While getting the PCV, I noticed that the rubber hose that conncects to the catalytic converter air injection pipe had disconnected. I shoved that back on (yeah for lankey arms) and test drove the Bronc. The sluggish acceleration dissapeared and the buzzing is no longer there accept sometimes at idle, but I can only hear it with the hood open.
I think this still all has to do with vacuum though, so I'm going to search and destroy any remaining leaks left in the emission system Thanks for your continuous help.
Kyle
Yes, correct grey. It was the PCV valve buzzing for sure. I just replaced the PCV 30 miles ago, but I pulled it out again to check it, and there was oil on the bottom again. While getting the PCV, I noticed that the rubber hose that conncects to the catalytic converter air injection pipe had disconnected. I shoved that back on (yeah for lankey arms) and test drove the Bronc. The sluggish acceleration dissapeared and the buzzing is no longer there accept sometimes at idle, but I can only hear it with the hood open.
I think this still all has to do with vacuum though, so I'm going to search and destroy any remaining leaks left in the emission system Thanks for your continuous help.
Kyle
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From: Gateway to the West
If the Thermactor hose was disconnected as you said, remove it again and make certain that while the engine is running, there is no exhaust escaping back through the check valve from the cat. (BE CAREFUL) You won't have to get very close to the end of the tube from the cat to be able to tell if there is HOT exhaust coming back up at you. If there is, the exhaust is backing up into the Thermactor system and will cause you all kinds of headaches because there is MORE recirculating exhaust than the compture thinks there should be. It will also eventually melt the rubber hose as well. I only say this now rather than earlier because part of your noise could also be the seal on the check valve going south. And too the Thermactor system provides the "push" for the EGR which is at the root of the Code 34.
Last edited by greystreak92; Dec 24, 2005 at 03:21 PM.
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With the help of a home made "paper towel exhaust flap type thingy" (patent pending), I didn't notice any exhaust coming back up out of the air tube going to the cat. I'm replacing the old cats with a new hi-flow next week, so I'll replace that check valve then as well just in case.
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