Gary Lewis Posted February 3, 2023 Share Posted February 3, 2023 I've been running more tests before blocking vacuum things off. KOEO is still clean, but have Continuous code of 22 (can't seem to get rid of this one, replaced MAP sensor, line, and redid wiring)? Just ran the KOER. Got one code (35). Looks like I'm back to looking at the EGR... I replaced the EGR and its position sensor already a few years back. (But very little usage) I will start with backprobing the EGR sensor voltage I think. I need to run out for a bit, but any other insight? If the EGR is acting wonky, I *think* it could explain my symptoms Yes, if the EGR is coming in while you accelerate gently the AFR will be very lean. And a stuck EGR valve would do that. Link to comment Share on other sites More sharing options...
ckuske Posted February 3, 2023 Author Share Posted February 3, 2023 Yes, if the EGR is coming in while you accelerate gently the AFR will be very lean. And a stuck EGR valve would do that. Thanks, I'll dive into that this weekend. I guess I should just pull the EGR off in general and see if it moves freely etc. Or should I leave it in place, ensure it is closed, and plug its vacuum line first to see if things improve? I also disconnected the HVAC vacuum line that comes off the tree on the firewall. At fast idle, the vacuum is at around 22". At normal idle, about 20". The missing at fast idle causes the vacuum to dip to 20" when you hear a "blip" in the exhaust. Hopefully this is all related! Link to comment Share on other sites More sharing options...
Gary Lewis Posted February 3, 2023 Share Posted February 3, 2023 Thanks, I'll dive into that this weekend. I guess I should just pull the EGR off in general and see if it moves freely etc. Or should I leave it in place, ensure it is closed, and plug its vacuum line first to see if things improve? I also disconnected the HVAC vacuum line that comes off the tree on the firewall. At fast idle, the vacuum is at around 22". At normal idle, about 20". The missing at fast idle causes the vacuum to dip to 20" when you hear a "blip" in the exhaust. Hopefully this is all related! I hadn't thought of the vacuum test, but that is telling. As the idle RPM goes up so should the vacuum. But yours goes down which says that something is killing the vacuum. EGR would certainly do that. But the fact that you don't have a problem at normal idle suggests that the EGR valve isn't leaking or it would do it at normal idle also. So that implies that the valve is being told to open. Pull the vacuum line off the EGR and see what happens? That's how it is controlled, so... Link to comment Share on other sites More sharing options...
ckuske Posted February 3, 2023 Author Share Posted February 3, 2023 I hadn't thought of the vacuum test, but that is telling. As the idle RPM goes up so should the vacuum. But yours goes down which says that something is killing the vacuum. EGR would certainly do that. But the fact that you don't have a problem at normal idle suggests that the EGR valve isn't leaking or it would do it at normal idle also. So that implies that the valve is being told to open. Pull the vacuum line off the EGR and see what happens? That's how it is controlled, so... I just realized that I got it backwards! I just edited the text above. Vacuum dips on the miss, it doesn't increase. I have never seen a gauge where 0 is on the right hand side of the dial! But, now I have. (That's how I got confused, just looked at the big number and counted the small hash marks from there, in the wrong direction!) Link to comment Share on other sites More sharing options...
ckuske Posted February 3, 2023 Author Share Posted February 3, 2023 I just realized that I got it backwards! I just edited the text above. Vacuum dips on the miss, it doesn't increase. I have never seen a gauge where 0 is on the right hand side of the dial! But, now I have. (That's how I got confused, just looked at the big number and counted the small hash marks from there, in the wrong direction!) Here is my vacuum diagram. It's always a joy to read, but looks like the only vacuum is to one of the solenoids mounted on the driver's side valve cover? Link to comment Share on other sites More sharing options...
Gary Lewis Posted February 3, 2023 Share Posted February 3, 2023 Here is my vacuum diagram. It's always a joy to read, but looks like the only vacuum is to one of the solenoids mounted on the driver's side valve cover? I see EGR? Link to comment Share on other sites More sharing options...
ckuske Posted February 4, 2023 Author Share Posted February 4, 2023 I see EGR? Yep, sorry I didn’t phrase my question well. At all. It looks like the only vacuum going into the EGR is from the solenoid on the valve cover. The line is smaller that I thought it would be, but I’m no expert. I just wanted to ensure that was the only line. I’ve pulled that line, will cap it, and drive the truck again. Also regarding the vacuum test, should the vacuum reading be steady? Or reasonably steady? It was jumping about 2” on either side of the 20” reading while running. Link to comment Share on other sites More sharing options...
Gary Lewis Posted February 4, 2023 Share Posted February 4, 2023 Yep, sorry I didn’t phrase my question well. At all. It looks like the only vacuum going into the EGR is from the solenoid on the valve cover. The line is smaller that I thought it would be, but I’m no expert. I just wanted to ensure that was the only line. I’ve pulled that line, will cap it, and drive the truck again. Also regarding the vacuum test, should the vacuum reading be steady? Or reasonably steady? It was jumping about 2” on either side of the 20” reading while running. Vacuum that jumps back and forth can mean valves that aren't sealing, but not always. In any event that's probably something you can check out later as I don't think it is the issue you are chasing now. I'll be anxious to see what the drive with the EGR valve disconnected finds. Link to comment Share on other sites More sharing options...
ckuske Posted February 4, 2023 Author Share Posted February 4, 2023 Vacuum that jumps back and forth can mean valves that aren't sealing, but not always. In any event that's probably something you can check out later as I don't think it is the issue you are chasing now. I'll be anxious to see what the drive with the EGR valve disconnected finds. I'll hopefully get to that tomorrow! In the meantime, I took a video to show the vacuum and you can see/hear the stumbling at fast idle. This isn't the main problem, but it may be adjacent. This video doesn't have the EGR disconnected (that's tomorrows job) https://drive.google.com/file/d/1MZygufOC7WSG52hxLHgggvVgT7gncPex/view?usp=sharing The audio is a little different in person, but hopefully this adds a little more color to what I'm trying to describe at fast idle. But, this item is secondary (but annoying). It's odd, but driving, this isn't noticed in performance, the tach, or in listening to the engine. Driving, it's all good, or when you kick the idle down. Link to comment Share on other sites More sharing options...
grumpin Posted February 4, 2023 Share Posted February 4, 2023 I'll hopefully get to that tomorrow! In the meantime, I took a video to show the vacuum and you can see/hear the stumbling at fast idle. This isn't the main problem, but it may be adjacent. This video doesn't have the EGR disconnected (that's tomorrows job) https://drive.google.com/file/d/1MZygufOC7WSG52hxLHgggvVgT7gncPex/view?usp=sharing The audio is a little different in person, but hopefully this adds a little more color to what I'm trying to describe at fast idle. But, this item is secondary (but annoying). It's odd, but driving, this isn't noticed in performance, the tach, or in listening to the engine. Driving, it's all good, or when you kick the idle down. EGR, hopefully that is the problem. Wish I could remember better, , had an EGR give me a stumble on a Suburban we used to own. Checked everything, all good, finally disconnected the EGR and found the problem. Link to comment Share on other sites More sharing options...
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