Wow I'm in a pickle. (Broke down truck) and a story.

[Atlas]

Retested the connector, seems to test OK. Resistance across the pins on the EGR appear healthy.

 

I didn't have much time last night so I decided to take the Blazer for a drive up and over a mountain pass to put some heat and air into the engine and observe.

 

On the ascent I left it in 3rd gear to keep the RPM up, 2500-3000. Coolant stayed cool, 195-199. I received a P0134 code unexpectedly (Upstream? O2 sensor inactivity) which was weird. I cleared the code and it never came back. O2's are doing their bouncing between lean and rich it appears.

 

After the pass there's a good long 5-7 miles of high speed cruising. I never got P0104/ egr flow insufficient in 4th/OD between 55 and 70mph, so that keyed me to observe that I don't get the EGR code at higher speeds and I don't get it at lower speeds if I keep the RPM higher, i.e. 3rd gear. If I leave it in 4th, P0104 will set as high as 50/55mph on light throttle. In 3rd, it won't set until I'm down to 30mph or so.

 

I don't know what that means, but I think it could mean something.

 

I doubt the old EGR was actually bad, pins test OK. I doubt the new EGR is bad. Something has changed or I've somehow blocked the EGR passage way down inside the intake where I can't see. Or there's a vacuum leak, but the MAP seems to report healthy vacuum at idle and cruising.

 

One thing I don't understand: Ignition advance on the scanner reads all over the place, but mostly negative. -15, -20, -30 seems fairly common. I don't think I've ever seen it positive, it's rarely ever near 0. I read that this can be an issue with scanners and OBD 1.5 simply not reading correctly. I doubt that too. OBD 1.5 was such a narrow period in time, and rare, there's just not a lot of information out there for modern times.

 

I'm at that point, first time in a long time, where I feel like I'm in over my head. This isn't making sense and I don't have the tools I truly need to get to the bees knees on this issue.

 

Edited 7 hours ago by Atlas

[KARNUT]

7 minutes ago, Atlas said:

Retested the connector, seems to test OK. Resistance across the pins on the EGR appear healthy.

 

I didn't have much time last night so I decided to take the Blazer for a drive up and over a mountain pass to put some heat and air into the engine and observe.

 

On the ascent I left it in 3rd gear to keep the RPM up, 2500-3000. Coolant stayed cool, 195-199. I received a P0134 code unexpectedly (Upstream? O2 sensor inactivity) which was weird. I cleared the code and it never came back. O2's are doing their bouncing between lean and rich it appears.

 

After the pass there's a good long 5-7 miles of high speed cruising. I never got P0104/ egr flow insufficient in 4th/OD between 55 and 70mph, so that keyed me to observe that I don't get the EGR code at higher speeds and I don't get it at lower speeds if I keep the RPM higher, i.e. 3rd gear. If I leave it in 4th, P0104 will set as high as 50/55mph on light throttle. In 3rd, it won't set until I'm down to 30mph or so.

 

I don't know what that means, but I think it could mean something.

 

I doubt the old EGR was actually bad, pins test OK. I doubt the new EGR is bad. Something has changed or I've somehow blocked the EGR passage way down inside the intake where I can't see. Or there's a vacuum leak, but the MAP seems to report healthy vacuum at idle and cruising.

 

One thing I don't understand: Ignition advance on the scanner reads all over the place, but mostly negative. -15, -20, -30 seems fairly common. I don't think I've ever seen it positive, it's rarely ever near 0. I read that this can be an issue with scanners and OBD 1.5 simply not reading correctly. I doubt that too. OBD 1.5 was such a narrow period in time, and rare, there's just not a lot of information out there for modern times.

 

I'm at that point, first time in a long time, where I feel like I'm in over my head. This isn't making sense and I don't have the tools I truly need to get to the bees knees on this issue.

 

You’re not over your head you’re just frustrated. I usually take a break and put the question on YouTube for ideas. I’m a little OCD so it’s a challenge. The information is out there. Patience is the key.

[Black02Silverado]

Great thread. As for parts did you try.  www.car-part.com?   

[asilverblazer]

6 hours ago, Atlas said:

I'm at that point, first time in a long time, where I feel like I'm in over my head. This isn't making sense and I don't have the tools I truly need to get to the bees knees on this issue.

Focus only on the recurring problem. Don't go looking for more. If the recurring problem is the EGR code; fix that. Ignore data that is irrelevant to diagnosing that ONE issue. 

 

It doesn't matter what the O2 sensors are reading or the timing is doing (yet) until the recurring problem is resolved. (If the diagnosis of the EGR requires O2 readings or timing advance readings then obviously use them.)

 

FWIW: I remember watching the timing advance on my 07 Silverado, and those numbers sound similar to what I recall.