EGR/misfire issue

1998 CHEVROLET 1500
265,000 MILES • 5.7L • V8 • 2WD • AUTOMATIC
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ASEMASTER6371
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your issue is not in the throttle body at all. it is the exhaust as I stated. you need to clean the passage from where the EGR is mounted to the exhaust manifold.

Roy
Mar 29, 2018 at 2:05 PM
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TMINER
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Okay. I am cleaning both ports where the EGR mounts to. My speedo cable isn't going far into the passage yet. I do see some black coming out though.
Mar 29, 2018 at 2:08 PM
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ASEMASTER6371
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ok
Mar 29, 2018 at 2:20 PM
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TMINER
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After I cleaned the ports as best I could, I blew air through both ports and ran the engine. I didn't test drive it yet but will tomorrow. It now sounds like it has a slight knock. Should I change the oil soon if it isn't just low?
Mar 29, 2018 at 7:49 PM
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ASEMASTER6371
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Sure, that would be a good idea

Roy
Mar 30, 2018 at 1:01 AM
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TMINER
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It doesn't fall flat on it's face anymore but does still shake at stop signs and when accelerating at different spots. I did have a squeak that was in a pattern when starting up the truck and until the engine was hot like a pulley noise or something. Never heard it before. Once I drove the truck some just now it went away. Maybe just an oil change will help? I did put a little Sea Foam in the oil too.

The SEL is flashing again even though it is running much better. I will have them reset codes when I buy oil and a filter.
Mar 30, 2018 at 10:16 AM
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ASEMASTER6371
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try that and drive it and see if any codes return

Roy
Mar 31, 2018 at 8:16 AM
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TMINER
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They wouldn't reset codes saying they have in the past and the customers car wouldn't start. I did have them read current codes and have cylinder 2 misfire and high voltage temp sensor (it was just changed). When I drove home is was clattering metal in the top or bottom of engine like it has a bearing or something else seriously wrong.
Mar 31, 2018 at 8:49 AM
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ASEMASTER6371
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You should have a shop listen to it and give you an idea of the noise. that motor had issues with lifters that collapse and that could cause not only the noise but the miss fire

Roy
Mar 31, 2018 at 10:25 AM
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TMINER
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I'm afraid of moving it much more because I don't want to destroy this engine.
Mar 31, 2018 at 10:30 AM
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ASEMASTER6371
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Some shops will come to you for a check as well. call around and see if they will and what they will charge.

if you have AAA, have it towed to a shop for the check.

Roy
Mar 31, 2018 at 10:39 AM
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TMINER
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Thanks so much. I'm not a mechanic and you've helped me immensely. Sorry if I've tried your nerves at all.
Mar 31, 2018 at 10:41 AM
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ASEMASTER6371
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Not at all. glad to help.

Roy
Mar 31, 2018 at 10:44 AM
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TMINER
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I made a mistake which caused the massive knock.

I now still have a knock and it is not all the time, but biggest problem now is when truck is in park or gear when stopped and engine is warm the rpm will fluctuate from 500-800 then smooth out back and forth. When engine rpm goes down to 500 the knock is worse then the knock gets a lot quieter when rpm evens out. Do you think a bad EGR valve or a messed up gasket could cause this? The truck also has a vibration when in park or gear still.
Apr 23, 2018 at 3:04 PM
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ASEMASTER6371
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No, the EGR would not cause the knock unless you knocked a piece of carbon into a cylinder from the intake system.

Yes, if you have a bad gasket it would cause the rough idle.

Roy
Apr 23, 2018 at 4:16 PM
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TMINER
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So, before I did a top cylinder clean with a cleaner it wasn't knocking. Is that the source more than likely?
Apr 23, 2018 at 5:43 PM
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ASEMASTER6371
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Sure could be. the top engine cleaner breaks up the carbon. the noise comes when it settles in a cylinder and cannot escape to the exhaust valve.

Roy
Apr 23, 2018 at 5:48 PM
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TMINER
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I did an engine flush and got a bunch of grit in the oil when it drained. I do not know what else to do besides have it looked at which I cannot afford right now. When I put in the oil I added a quart of MMO. When I start the engine it knocks loud for two to three seconds then quiets.
Apr 23, 2018 at 6:03 PM
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ASEMASTER6371
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It is not an oil flush. the carbon is in the intake system.

What should be done is someone needs a boroscope to look inside each cylinder to see where the carbon is located and then determine if it can be removed without a major effort.

Roy
Apr 24, 2018 at 4:22 AM