Hi Gang...I've had an ongoing problem with my '95 3.4 EGR system and I need some fresh ideas. Basically, when I got the car the SES light would come on ocassionally, so I bought a code scanner that would go OBD1 with an OBD2 connector. It read code 77, EGR bank 3 not working. I took off the valve itself, cleaned it up real good, as well as cleaned up all the areas around it, installed a new gasket and that didn't solve the problem. Next I took of the EGR tube, cleaned it out real good and installed new gaskets...same problem still exists. I finally decided that if my scanner says the EGR valve itself isn't working, maybe it's just bad. So I ordered one from a dealer I found on E-bay which I got for $85 instead of the $235 they charge at my local Autozone. Another new gasket and still the same problem except my scanner reads that all three banks aren't working. Could be a bad EGR valve replacement part I suppose. I took the entire system apart, from mounting adaptor to the EGR tube, cleaned all parts well, and reassembled with new gaskets. i also cleaned the wiring connector with contact cleaner. Still pulling same codes. My new plan is to reinstall the old EGR valve to see if I just get the one code as before and use that as some sort of check to tell if the new EGR valve may in fact be bad. My question is this...is there anything else I'm missing?
95 3.4 EGR problem
brucehusker
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Hi Gang...I've had an ongoing problem with my '95 3.4 EGR system and I need some fresh ideas. Basically, when I got the car the SES light would come on ocassionally, so I bought a code scanner that would go OBD1 with an OBD2 connector. It read code 77, EGR bank 3 not working. I took off the valve itself, cleaned it up real good, as well as cleaned up all the areas around it, installed a new gasket and that didn't solve the problem. Next I took of the EGR tube, cleaned it out real good and installed new gaskets...same problem still exists. I finally decided that if my scanner says the EGR valve itself isn't working, maybe it's just bad. So I ordered one from a dealer I found on E-bay which I got for $85 instead of the $235 they charge at my local Autozone. Another new gasket and still the same problem except my scanner reads that all three banks aren't working. Could be a bad EGR valve replacement part I suppose. I took the entire system apart, from mounting adaptor to the EGR tube, cleaned all parts well, and reassembled with new gaskets. i also cleaned the wiring connector with contact cleaner. Still pulling same codes. My new plan is to reinstall the old EGR valve to see if I just get the one code as before and use that as some sort of check to tell if the new EGR valve may in fact be bad. My question is this...is there anything else I'm missing?
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if the plenum is clogged it will do that. did you check for power with key on terminal d should be power . key off no power.
You might disconnect the battery for 30 seconds to see if the action will remove the trouble code and let the ECM relearn. Otherwise, it might take 50 starts to reset the diagnostic code(s).
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I did clean out the entrance to the plenum when I cleaned out the EGR tube. Could it be clogged further in? Also, what procedure should I use to check for power? Would a multitester do the job and is there any chance of screwing up the ECM? Thanks for the comeback!
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If I shut the car off and then restart, the SES light is out and doesn't seem to come on again until back off the throttle. The codes are stored as historical until the SES light comes on again.
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I have the same problem. I talked to a mechanic who told me that 95 was the last year they produced that type of computer and they are notorious for throwing codes. I can actually make it go on and off by running the car in for example 4th when it should be in 3rd (rpm drops below about 1800 and engine lugs slightly). If you don't tighten the gas cap properly, same thing. Here in Arizona we must pass emissions every 2 years, because of these type of problems (not just Chevy) they don't even check the codes or the SES light unless the car is 1996 or later. Fool around with it a little and you will probably figure out what driving habit is causing it rather than a real problem.
Yes, that whole passage through the intake could be plugged. I've seen a couple so bad it was just easier to take the intake off and clean from the inside too. Started with a piece of wire to get poked thru all the carbon build up, then switched to a bottle brush and carb cleaner.
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An easy way to check the intake passage is to remove the EGR valve and start the engine. If the passage is open, you will have a HUGE vacuum leak. If it runs normally, the passage is plugged. You won't need to run the engine more than a few seconds. There should also be exhaust noise from the open exhaust passage.
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Is there a method to check if the EGR valve itself is good. I'm wondering if my replacement valve is operating properly. I'm also unsure as what conditions have to exist before the ECM puts out a call to the EGR valve to open whichever of the three ports it opens.
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do as red said as leaving egr off and start car. they clog up sometimes that only way is to take intake off and drill or somehow get all that carbon out. i sent you 3 pages on how the egr and computer works and diagnostic of system. yes you use a digital meter to check for voltage or a regular test light.
This EGR is a three stage system. The problem is only with the 3rd stage witch is maximum flow. You either have a bad solenoid on that stage or have a restriction somewhere that is not allowing enough flow. To check the solenoid, measure the OHM resistance on the two working ones and compare the readings to the 3rd one. They should all be pretty close to the same resistance. The port in the intake can plug up enough to cause the restriction, but allow enough to flow for the lower stages to work properly. Also the tube must be completely clean. The carbon in the tube is usually very hard and can be difficult to remove. I would also say the new EGR valve is probably junk. It would be a plus if you knew someone that had a tech1 scan tool . With it you can actually actuate the egr solenoids. on the 3rd stage the engine should stall or at least near stall.
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When the SES light comes on, it stays on until the car is shut down, Then upon restart, the light is off. With my AutoXray scanner, I can read the historical codes and they are the EGR fault codes. If the engine has been shut down, they show as historical only. If I read the scanner while the engine is running and after the SES light comes on, is shows as a current code and it's the same codes as the historical. The ECM won't let me erase historical codes, but it will erase current codes while the engine is running. I'm really leaning at this point to a blockage in the plenum. Also I have noticed the smell of gas coming from the exhaust after running for awhile and was wondering if the EGR problem can result in the ECM oversupplying fuel or the fuel isn't getting properly ignited somehow. I just had my fuel system checked by a mechanic and they could find no problem with leaks or such. The car is in the shop today for some transmission work, but when I get it back I'm going to run through some of these tests and solutions you kind folks have suggested. BTW, thanks to all for this help. I appreciate it!
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Does your scanner have bi-directional controls? I don't have any personal experience with AutoXray. I know they make different grades of scanners that increase in cost as features are added. Look in the scanner menus for "output controls" or something similar. If it has this feature, you can use the scanner to manually open each stage of the EGR valve. If you do this at idle, the engine will run rougher and rougher as each stage is opened. You can use wiring schematics and a voltmeter to trace voltage responses to ECM commands if you find that a particular stage does not work as intended. A big time saver in situations such as yours.
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