Odd random EGR code 92 blazer 383 TBI

[92BlazerSport]

For the past several months since putting a mild 383 in my blazer, I get a random egr code only at highway speeds and never consistently. Seems to have no effect on performance or mpg. I’ve replaced the egr and the controller, the vacuum lines to and from and added grounds. I’m at a loss as it might be fine for a month, then throw a code, or it might throw a code for a day or two consecutively. Sometimes the check engine remains on for the entire drive, sometimes it vanishes. I can make the same drive under very similar conditions for days and not get a code, then one day… I’m baffled. Thoughts?
Thanks in advance!

 

[PlayingWithTBI]

For the past several months since putting a mild 383 in my blazer, I get a random egr code only at highway speeds and never consistently.

These TBI manifolds have been known to build up so much carbon and debris in the passages that go to the EGR valve. The only way to clean them out is to pull the manifold so, people are hesitant to explore it. You may see some buildup in it if you remove the EGR and look down there.

 

[92BlazerSport]

These TBI manifolds have been known to build up so much carbon and debris in the passages that go to the EGR valve. The only way to clean them out is to pull the manifold so, people are hesitant to explore it. You may see some buildup in it if you remove the EGR and look down there.

The complete motor build has about 6k miles on it. The intake is new, the tbi is fresh… essentially I replaced everything but the radiator when I did the motor. I’ve went so far as to pull the ECU and ensure all the contacts were good. Thanks for the thought though! Much appreciated.

 

[someotherguy]

The conditions needed for the ECM to run the EGR system test are such that it rarely happens. The factory manual details it in the troubleshooting steps for code 32. Look in the Engines section here on the forum and in the sticky'd posts near the top you'll see a link to online PDF's of the factory manuals; very handy to have.

If you've "uncorked" your exhaust (anything other than stock manifolds, catalytic converter, and muffler) then it's possible your unheated (1-wire) O2 sensor isn't getting hot enough to generate the expected signal. Converting to a heated (3-wire) sensor may help. When the test conditions are met, the ECM will momentarily operate the EGR valve then watch the O2 sensor readings to "see" if it had any effect, so you see why the O2 comes into play here.

It's also possible you replaced a functioning EGR valve unnecessarily, and the aftermarket valves are often not directly compatible regardless of what their application notes claim.

Trust me go read the manual on the code 32 troubleshooting. It'll shine light bigtime on why you're randomly getting the code. If the truck doesn't run any different, especially if you're not noticing pinging under part throttle or load, probably nothing to worry about. Again, consider the 3-wire O2 conversion. It's been discussed a bit here recently - those posts will be in the Engine section, too.

Richard

 

[92BlazerSport]

The conditions needed for the ECM to run the EGR system test are such that it rarely happens. The factory manual details it in the troubleshooting steps for code 32. Look in the Engines section here on the forum and in the sticky'd posts near the top you'll see a link to online PDF's of the factory manuals; very handy to have.

If you've "uncorked" your exhaust (anything other than stock manifolds, catalytic converter, and muffler) then it's possible your unheated (1-wire) O2 sensor isn't getting hot enough to generate the expected signal. Converting to a heated (3-wire) sensor may help. When the test conditions are met, the ECM will momentarily operate the EGR valve then watch the O2 sensor readings to "see" if it had any effect, so you see why the O2 comes into play here.

It's also possible you replaced a functioning EGR valve unnecessarily, and the aftermarket valves are often not directly compatible regardless of what their application notes claim.

Trust me go read the manual on the code 32 troubleshooting. It'll shine light bigtime on why you're randomly getting the code. If the truck doesn't run any different, especially if you're not noticing pinging under part throttle or load, probably nothing to worry about. Again, consider the 3-wire O2 conversion. It's been discussed a bit here recently - those posts will be in the Engine section, too.

Richard

Thanks Richard! I’m going with “no” on the heated sensor as the o2 is mounted in the shorty headers so it’s definitely getting warm enough (or at least I’d think so lol). Along with that it almost never happens on short drives, usually when it throws a code it’s somewhere between 10 and 60 miles into a drive. That said, I will definitely find those manuals and run through those. I can’t thank you enough for sharing that!

 

[Scooterwrench]

I'm guessing you're running a tuned prom for that stroker? May need the .bin tweaked a little.

 

[92BlazerSport]

I'm guessing you're running a tuned prom for that stroker? May need the .bin tweaked a little.

Actually the cam I am using is essentially what you’d find in a mid 80s z28 tuned port. The build should run fine on the stock ecm tune. The A/F averages right about 14.7 with the stock ECM so I haven’t done a prom. Good call though! I’m sure at the end of my rope with this goofy issue. I do get a little valve rattle running 87 octane but I’m running right about 12 degrees advance as that’s where the performance is happy. 89 octane solves that pdq.

 

[Scooterwrench]

Try Richards approach. That motor would benefit from a tuned prom. Got any dyno shops near you? Or you can get into tuning yourself if you have good engine knowledge and some time.

 

[92BlazerSport]

Try Richards approach. That motor would benefit from a tuned prom. Got any dyno shops near you? Or you can get into tuning yourself if you have good engine knowledge and some time.

This build was done specifically to not need an ecm tune. Don’t be mislead by myths on the old ecm’s and tuning. They simply control timing and fuel so far as performance. Running a 14.7 A/F says the tune is fine.

 

[Schurkey]

Perhaps a moderator will move this thread to the "Engine" section of the forum.

I do get a little valve rattle running 87 octane but I’m running right about 12 degrees advance as that’s where the performance is happy. 89 octane solves that pdq.

"Valve rattle"??? Detonation has nothing to do with valve clearance.

12 degrees of advance? That's a long way from the "0" factory spec. Have you ever bothered to check for knock-sensor activity? Does the electronic spark advance work?

For the past several months since putting a mild 383 in my blazer,

The intake is new, the tbi is fresh… essentially I replaced everything but the radiator when I did the motor.

WHICH "intake" are you using? Stock? Aftermarket?

WHICH cylinder heads? Stock swirl-ports? Vortec? Aftermarket?