Hello fellow ThirdGen'ers!

I've run into a challenge on my 90 IROC-Z 5.7L TPI, recently I noticed while driving say 0-45ish mph it's smooth sailing... but when I go to get on the highway acceleration is super sluggish often times having to let off the gas and and then press the gas almost like I'm "taking steps to get up to speed" like it lacks power or not running on all 8 or something. Anywho, I get up to 50mph or so (unknown RPM's) and a noticable vibration comes from the engine bay for a moment then BOOM the SES light. Once I get to my destination, turn off the car, tend to business and start it back up... the SES light is gone. If I take the street home... no SES light, hit the highway and BOOM SES light. So today I pulled the codes and they come up as 12X3 then 13X3 then 32X3. I understand the 12 is normal but the simotanious 13 & 32 only at highway speeds? Yes I have a GMSM, Yes I looked both codes up. The 13 is o2 sensor related and the 32 is EGR related and both have challenging troubleshooting flow charts....

Where would you begin? What's your thoughts? Would I be able to identify the potential issue with a datalog? If yes, where/how?

Friendly community support would be greatly appreciated!

 

Stock exhaust?
Can you datalog it? That'll probably tell you what's going on.
It is possible to be 2 separate problems.
Check for exhaust leaks and vacuuming leaks (specifically the egr lines).
Check the wiring, make sure nothing is melting etc.
If things are normal then start the troubleshooting tree. Complicated or not, it'll get some information on the issue.

 

The egr code almost always comes on with highway travel when the EGR valve fails it's self test... Car needs to be at temp, higher rpms, etc. Have had two third gens fail on this.
use a hand pump to put vacuum on the EGR and feel for the diaphragm to lift... If it fails to lift, replace the EGR.

Or just replace it... But do check the vacuum lines to the EGR... The computer is seeing that it's not opening.

 

I'm also thinking EGR valve. On the highway after warming up is when the ecm would start commanding EGR open so it makes sense from that perspective.

 

Took a drive today, the SES light didn't pop while getting onto nor while on the highway. After reading the feedback, I'm considering just ordering a new EGR w/ vac lines. Before I do so, I did hit the GMSM just to grasp the relation of the two codes. The diagnostic aid for the Code 32 stated "The ECM monitors the integrator during a Code 32 test and MUST detect a change to pass the test. If the integrator is at a FIXED value (Lean Or Rich) when a Code 32 test is run a Code 32 may set" so I fired up TunerPro and looked at my only log of 2022. Temp got up to 190+, Loop status remained on Open and both INT/BLM stayed at 128ea and my History Tables wouldn't populate, not the defaults nor a custom RPMvsINT. I also found Code 13 stored in the log file and no Code 32, but the log was created at least 1mo back. There was also something called O2 Rich/Lean status, it was rapidly changing in the begining of the log then just stuck on Lean.

Does this change your thought processes or still leaning more toward EGR?

 

To give myself a fresh start, pulled & charged battery. Well, since battery was pulled no codes should be stored. I hit the highway, somewhere between 45mph - 55mph she really bogged down, no SES light though. Arrived at my destination, stopped logging, and this is what I've found. #1) when reviewing the log I can see the EGR being commanded, but #2, she seems to be running rich. I also stood at the rear, and while no White/Blue smoke I could surely smell fuel.



What does the screenshot tell you?!?

 

What did the EGR valve do when you tested it?

 

Didn't have a Vac Pump that I recalled, then I stumbled on one just a moment ago in my HF Brake Bleeding kit. I went outside and it's far to dark to go mission impossible trying to get to the valve under the TPI. It's not at all convenient like my L03. I'll report back tomorrow.

 

Reporting back as promised. I think I did the test correctly BUT I got ZERO movement from the diaphragm, even pumped the HELL out of my handheld pump and the needle on the Vac Gauge would move like it was trying to pull vac but just wouldn't actually hold any level of Vac. Does the size of the hose from Vac Pump to EGR matter? Example, the vac line off the EGR is a super thin plastic with the boot on the end, the vac line I'm using is "standard"? Pics below on my efforts...

 

Does the vac hose fit snug on the egr nipple? If yes then you've likely got a bad valve. The movement is quite clear when working.

 

Yeah in my opinion it's a snug fit, it didn't slide right on I had to wiggle/push it on there a bit. Just so I know up front, if I get a new EGR Valve can the vac test be completed out the box at the parts store OR it has to be bolted in place? I read a thread here where someone tried the vac test on a NIB Valve and got zero movement from the diaphragm, I'd like to prevent a dud if I can.

 

You can test it in hand, yes

 

I was lucky, was able to pause the log while EGR was being commanded, at the MOMENT the Code 32 set... see anything here that I should be alarmed by? How about the damn o2 below 100Mv in closed loop! Excuse my ignorance but is o2 voltage determined by incoming air? If yes, how do I balance the air / fuel mix?