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 1 hour 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.