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 Wednesday at 02:45 PM 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.

 

 

[Atlas]

17 hours ago, asilverblazer said:

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.

 

 

 

That's part of the problem...the EGR has already been replaced, and I've already had the complete intake assembly removed, and the EGR passages were clear at that time. That leaves wiring, PCM, or another variable that I wasn't expecting. Best I can tell, it's not wiring or the PCM, so I'm grasping for straws.

 

The PCM uses the MAP reading to confirm the requisite loss of vacuum in the manifold when the EGR activates. Since that's vacuum related, it involves a lot of other systems which could play a role.

 

The overall diagnosis has to be considered too. The fuel lines in the intake had rubbed through and were dumping fuel into the intake, drowning the cylinders in fuel, and putting raw fuel into the sump and cat converter. The fuel system has been fixed but the complete path of damage may not be. If the cat was damaged and melted the internals, it could be partially obstructed and also playing into the EGR issue.

 

I'm retracing my steps; trying to go back to thinking thinking Horses not Zebras based on the clues I've been given. These engines aren't *that* complex.

 

Could it be, now that the truck is running well, that carbon and crud from being run with the fuel system in disarray is now dislodging and clogged my clean EGR passages where I can't see?  That's what the code is actually saying. The flow is restricted, dummy. Retrace step 1.

 

I may just need to remove the lower intake again. Before I do that I'm going to try removing the EGR and running the engine for a few seconds to see if it will blow anything lodged in the egr passages out through the open ports.

 

19 hours ago, Black02Silverado said:

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

 

That's been helpful in the past. For the spider injector, there's no guarantee I'll get a working one. The spider I have seems fine now that the high pressure fuel line isn't making an early delivery via large hole. SO at least I'm not marooned and looking for one of those.

 

Row52 (dot com) is also a good one for watching for vehicles at local yards.

 

[asilverblazer]

6 hours ago, Atlas said:

The PCM uses the MAP reading to confirm the requisite loss of vacuum in the manifold when the EGR activates.

 

If the cat was damaged and melted the internals, it could be partially obstructed and also playing into the EGR issue.

 

I'm retracing my steps; based on the clues I've been given. These engines aren't *that* complex.

Can you monitor vacuum/MAP readings? Particularly, during EGR activation?

 

Can you bench test/check the EGR valve operation? 

 

Presumably the MAP sensor is OK.

 

No other vacuum leaks, masking the correct operation of the EGR?

 

Cats may be fried, but I don't think they are going to change your diagnosis of EGR operation.

 

[Atlas]

37 minutes ago, asilverblazer said:

Can you monitor vacuum/MAP readings? Particularly, during EGR activation?

 

Can you bench test/check the EGR valve operation? 

 

Presumably the MAP sensor is OK.

 

No other vacuum leaks, masking the correct operation of the EGR?

 

Cats may be fried, but I don't think they are going to change your diagnosis of EGR operation.

 

 

I can see MAP data on my scanner. Warm idle MAP reads about 10.3-10.6 inHg which is healthy. Baseline is ~29 inHg (atmosphere) with key off.  So that means the engine is pulling about 18.4" of vacuum at idle (29 minus 10.6) which is healthy. No real vacuum leaks that I'm aware of. The MAP sensor appears adequately responsive but I replaced it just in case, and I erased codes and reset the PCM after replacing it. Still getting the code.

 

It's frustrating that I don't have data to verify actual data of the requested vs actual pintle positions of the EGR when the PCM is commanding it. That would really help.

 

That's why I'm going back to basics. A plugged EGR port may be staring me right in the face. Ports were crystal clear when I reinstalled the manifold but that may not mean anything now. It doesn't appear clogged as far as I can see where the EGR bolts on, but farther back/down in the manifold it may be filled with crud again. There's all kinds of carbon still coming out of the exhaust. On cold start as the engine warms, the exhaust drips a little moisture and spits if you goose the throttle. It's truly just condensation, but it leaves a black mess on the floor.

 

[Atlas]

Atlas won.

 

I know better, but I did it anyway. I took a compressed air line with a chuck and rubber tip and jammed it in the open EGR port. The port was clear as far as I could see, and as far as I could poke with a flexible wire, but that doesn't mean it's not clogged.

 

Compressed air blew back at me along with a cloud of black. Oops. I didn't have the rubber tip seated in there all the way. Jammed it up in there some more and squeezed the chuck. PSI was set to 120. Poof! It blew back at me again. Third time...pfffffttssssssspffffffsssfffffff, face full of carbon, and then, kind of a thud..and the air stopped spraying back at me. It was now exiting the exhaust with a low shhhhhh sound as it flowed through the pipe. Something broke free. I pressurized the port again, and air flowed.

 

Made my day.

 

Long story short on this problem, it's fixed. Something was really blocking the EGR passages down low, and compressed air blew it apart. I don't recommend this as who knows what debris was sent where. But it's allowed me to move forward, mentally, and onto the next problems I need to get this little S-Blazer going down the road properly again.

 

[jl6690506]

The 92-95 SCPI spider injectors are notoriously problematic and hard to source new replacements. I’d pull the intake manifold first to inspect cracked lines and brittle plastic legs before dropping $350 on a rebuild. The 1.5 OBD system only offers limited data, no misfire tracking, which is normal for this 1995 model. Enjoy the project!

[Atlas]

^^ Yep, that's all it was. The fuel line had rubbed through on one of the spider legs and was severely leaking. Even the lines/nut and bolt kit are harder to find and I think I paid $84 (Standard HK-11) for the kit. Ripoff. But when you're the only brand still making it...

 

There are a few things left before the truck is Atlas® Certified (and I've thoroughly spent too much on it considering what it's worth). My RockAuto shopping cart total is about $250 and growing:

 

-Radiator (there's a pinhole leak, driver's upper corner where a cooling line bolts in, the threaded insert weld cracked)

-Water pump (mine squeaks, I assume it's shot)

-Lower radiator hose (it's original, if replacing cooling parts, this shall be touched too)

-Starter (It's not always engaging the flywheel, get the whirrrrrr sometimes when I turn the key but no crank)

-Door hinge replacement pins (already purchased, need to install)

 

Suspect/borderline parts NOT included in shopping cart (only if I want to opt for bonus points):

-Motor mounts. Someone twerked the radiator fan shroud, so I can't tell if the motor mounts are bad/squished or if it's truly just a deformed fan shroud. I reassembled the shroud correctly but the plastic is still re-forming/relaxing where it was all mangled and bent, and the fan still chafes it occasionally, but it's 99% better.

-Left rear door speaker is blown

-Rear wiper motor is shot (horrible grinding noise)

-One of the wheels is missing the bowtie center cap. This drives me insane to look at, I'll just need to find a replacement.

 

I've already replaced:

-Driver's door mirror

-Idler pulley

-Tensioner pulley

-EGR

-MAP sensor

-Hood prop retainer

-Intake plenum fuel lines

-Intake gaskets

-Thermostat (and flushed cooling system)

-Radiator cap

-Radiator overflow reservoir cap

 

And it needs tires, and could use a set of front brake pads, and the brake system flushed. And it could use a transmission service, and if I'm doing that, why not differentials, and transfer case, and oh hell, why not flush the power steering.

 

Is there anything I won't touch? Or...do I just get it to a point where I can send it down the road?

Edited 8 hours ago by Atlas

[StingerZ16]

Such a journey.

Thanks for bringing us along.

[Grumpy Bear]

Is that starter old enough to have a mechanical external engagement Bendix Solenoid? 

 

You really like this vehicle. I would too. Labors such as these are not done for profit. Affection is much closer. Love it to death young one and enjoy the fact you still can.

 

I'm jealous. Not of the vehicle, although I do like it, but of the focus, energy and commitment. You da man! 

[OnTheReel]

You got any pictures of this beast? I’m assuming the body is in better condition than anything remaining here in Wisconsin or the list wouldn’t be quite so long!

[Atlas]

2 hours ago, OnTheReel said:

You got any pictures of this beast? I’m assuming the body is in better condition than anything remaining here in Wisconsin or the list wouldn’t be quite so long!

 

I may post it once I'm ready to send it down the road. It's very....recognizable. Documented, even. This isn't just any 1995 Blazer

 

The feature it has is the only one I've ever seen in the wild. Not necessarily value-increasing, but it is rare.

 

You are correct about the body; it's a Pacific Northwest (Wet side) vehicle since new so it has zero rust. It's straight. It was parked outside for a long time so it does show its age a little bit but otherwise presents very well and is very clean. If I didn't have guys on this forum wanting to hunt me down and kill me for my politics and sass, I'd post it up right now.

 

And there it is, adding some faux-intrigue about this weird little truck for those following the story..

 

I just returned from tearing the lower intake off a junkyard '95 2-door 4.3 CPI. $50 for the intake and $45 for the EGR still attached to it. I said to the guy, MY DUDE, it came attached, and probably doesn't work, and you're charging me 2/3 the cost of a brand new EGR, I know, I just bought one. Are you serious? He said if I didn't want the EGR I could go take it off. Alrighty then. So I took it off. My total with tax was $56 out the door.