stock 2.8 v6 I discovered a plate on the underside of the upper plenum. Shouldnt this be open, to allow the EGR valve to pass exhaust into the intake manifold? I don't know if the PO attempted an EGR delete here? also The old valve had some weird weld job and the business end is completely blocked or sooted up, compared to a new valve.
stock 2.8 v6 I discovered a plate on the underside of the upper plenum. Shouldnt this be open, to allow the EGR valve to pass exhaust into the intake manifold? I don't know if the PO attempted an EGR delete here? also The old valve had some weird weld job and the business end is completely blocked or sooted up, compared to a new valve.
I can't really say for sure... but depending on the car, there are a dozen or so of those gaskets with varying sized holes in them. The picture isn't that easy to see... but is it possible that it's just gummed up? They sold them with large or small holes, depending on application. The V6 Fiero I think only used one size of course, and it wasn't wide open if I remember correctly. At least one size had a hole the size of an eraser head if I remember properly. Many of them got replaced with a fully-opened hole, or whatever. I remember when you'd buy an EGR gasket set (that was generic for a few cars), it came with different sizes and a sheet.
My guess is the owner probably tried to block it off because he was having issues with it.
Personally, I can't stand the EGR system on our cars. It's messy, makes the entire intake dirty, and adds carbon buildup all over the valves. But I realize its importance for improving emissions. The computer system we have in the Fiero is really outdated, to be honest... and this is something I'm recognizing more and more. Yeah, they still work well, but there are so many options out there now that can make these engines perform more efficiently. I think back to my Pontiac Solstice in 2006. It had a 2.4L VVT L4... very efficient engine. It didn't have an EGR system because the computer was able to compensate to a much higher degree of precision to the point where it no longer needed an EGR. It also only had one catalytic converter... not a primary and secondary cat either.
If you at some point decide to go with a much more efficient system, you can just completely eliminate the EGR altogether. One of the problems is that the old ECM runs at 300 baud. That might not mean much to most people here, but if you ever used to connect to a Bulletin Board System back in the day, 300 baud is an extremely, extremely slow serial throughput rate. To the point that the time it would take for the screen to type out this entire message I just pushed, would be at least a couple of minutes. If you imagine that every sensor is sending the analog voltage measurement back to the ECM for the fuel mapping look-up... it's amazing to me, honestly, that it even works at all.
Ha ha funny you say that… Yes I was wondering why the plenum was so dirty…
I'll try cleaning that plate and see if a hole opens up, or maybe it is solid and the exhaust gas got backed up where it started clogging the valve, I'll try to clean the valve too and see if it's just soot buildup or a deliberate block.
I'm leaning towards opening up the hole, whatever the stock configuration was, I already got a new valve.
[This message has been edited by gregr75 (edited 07-08-2023).]
Ha ha funny you say that… Yes I was wondering why the plenum was so dirty…
I'll try cleaning that plate and see if a hole opens up, or maybe it is solid and the exhaust gas got backed up where it started clogging the valve, I'll try to clean the valve too and see if it's just soot buildup or a deliberate block.
I'm leaning towards opening up the hole, whatever the stock configuration was, I already got a new valve.
The EGR doesn't always come on either, I think it's mostly at cruising, but I'm hoping Ogre will correct me.
I usually try to clean up the soot with some throttle body or brake cleaner... it should clean it up pretty nicely. I'll also run the engine with the tube off, crack the throttle a little and slowly spray a little bit of carb cleaner in through the throttle body.
Also, if you use Seafoam in your fuel tank (put it in at the gas station, JUST before you're about to fill up so it mixes with a full tank), it'll clean all the soot and deposits off your valves, etc.
Yes, likely "deleted" the EGR as a "cheap" fix for bad valve etc. Sometimes you could do it w/o causing other problems or ECM setting "codes" but often "Fiero" V6 also need a "chip" deleted the EGR.
So now pull the ECM cover off to see what "chip" is there. Because Many Aftermarkets "Chips" also Deleted the ability to scan the ECM.
82-T/A [At Work] "300 baud" means Nothing but Speed of Serial Data for Data Stream When in ECM is Diag Mode for scanner use. 87+ Duke w/ DIS have Faster CPU and Faster "baud" but Still only Updates data to scanners to 1 or 2 times a second. Faster CPU mean GM move Cruise "Box" to the ECM and saved Money to make the cars with ECM like that.
ECM are made to handle 1 "thread" and do that well for the "slow" CPU types used in them. Same "class" CPU used in Atari and hell of a lot other things in late 70's to early 90's that 90+% ran only 1 "thread." Most older ECM "Hate" scanners because Steels CPU clock cycles to run the Engine. Big part of Why GM and other ECM have Higher Idle when the scanner is getting data. Typically ~ 1000RPM is idle all the time a scanner is run. Because can't run 2 "threads" and stay running the engine right @ normal Idle.
Later ECM/PCM doesn't like that too but CPU Clock is faster because Faster CPU got Cheaper. Even Now w/ OBD2 the ALDL Port isn't made to have Scanners and other crap like Progressive "Snap Shot" connected 24/7/365 sucking whatever data from any to all devices not just PCM data. Worse many of that crap has Bugs to Malware and because OBD2 is "2way" can cause problems, kill the vehicle right now or completely "brick" them.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
I'll try cleaning that plate and see if a hole opens up, or maybe it is solid and the exhaust gas got backed up where it started clogging the valve, I'll try to clean the valve too and see if it's just soot buildup or a deliberate block.
I'm leaning towards opening up the hole...
It's probably a tarball... just like what I discovered on my Formula and reported on Here years ago.
Both the valve and the gaskets at the Plenum were deliberately blocked. The valve had a gob of weld instead of the soot/tarball we suspected. I laughed when I scraped away the orangy permatex and I found a dime covering a gasket hole. So I'm 10 cents richer And yes the hole was about the size of a pencil eraser head.
So I never checked the ECM codes in the 2 months i had the car and it was roadworthy, i cant now as the car is in pieces. it seemed to run fine but what do i know.
I pulled the ECM cover and looked at the PROM. I wouldnt know if this is factory original or a modification. Could anyone tell by the photo? It says APN 0154. Theres some more text hidden by the PROM cover, but im hesistant to pull it because i dont have the removal tool and im nervous about breaking something.
[This message has been edited by gregr75 (edited 07-08-2023).]
I pulled the ECM cover and looked at the PROM. I wouldnt know if this is factory original or a modification. Could anyone tell by the photo? It says APN 0154.
According to This chart, it's a factory PROM... which means running the engine with a non-functional EGR system is not a good idea.
Or I should say… DISABLING the EGR system due to dirty intakes, parts going bad seems like it would effect performance negatively without doing the chip mod.
DELETING seems the way to go with proper chip mod if you dont want to have those parts any longer.
I guess this is all a moot point anyway because in my case, I've decided to enable the EGR system back as I already bought the valve, I hope it doesn't create new problems with this particular car that I'm not aware of as I rebuild. Hopefully the PO was just looking for a shortcut versus the system was playing havoc with the car.
I guess this is all a moot point anyway because in my case, I've decided to enable the EGR system back as I already bought the valve, I hope it doesn't create new problems with this particular car that I'm not aware of as I rebuild. Hopefully the PO was just looking for a shortcut versus the system was playing havoc with the car.
The EGR system does nothing to hamper performance, and it's possible it actually slightly improves gas mileage. Combine that with the fact that it also reduces harmful emissions... and it's a win-win situation to have a functional EGR.
Often, people will block the 2.8's EGR passages (as appears to be done with your engine) when the EGR pipe cracks and develops a leak... instead of doing the sensible thing and replacing the pipe. It sounds like you're going about this the right way.
Originally posted by gregr75: Thanks for the info Patrick, thats good to know. Other than the intake getting dirty, is there a reason for disabling the EGR system?
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Originally posted by Patrick: Often, people will block the 2.8's EGR passages (as appears to be done with your engine) when the EGR pipe cracks and develops a leak... instead of doing the sensible thing and replacing the pipe. It sounds like you're going about this the right way.
Delete EGR or don't delete EGR. I don't care, one way or another. There are likely not enough of our cars still running to make a difference.
BUT... if you delete the EGR system, you need to have it programmed out of the chip. Just blocking it off can cause high combustion temps, due to lean mixture and far advanced ignition timing. (I've seen the fueling and spark tables.) Short term, maybe it'll ping. Long term, it can possibly burn holes in pistons. (I've seen a few.)
Delete EGR or don't delete EGR. I don't care, one way or another. There are likely not enough of our cars still running to make a difference.
BUT... if you delete the EGR system, you need to have it programmed out of the chip. Just blocking it off can cause high combustion temps, due to lean mixture and far advanced ignition timing. (I've seen the fueling and spark tables.) Short term, maybe it'll ping. Long term, it can possibly burn holes in pistons. (I've seen a few.)
We will have to agree to disagree, but that's okay. I've done it to many, and never saw a failure. I believe I even made a post about it using a penny, or it might have been in my code 32 thread.
Also another thing… There's only supposed to be one gasket for each joint, right?… It looks like the PO doubled up on gaskets for some reason. The joints I'm talking about are:
Exhaust pipe to EGR spacer EGR spacer to EGR valve EGR valve to EGR pipe EGR pipe to intake
YES; One Gasket for EACH Joint: One Gasket) Exhaust pipe to EGR Adapter / GM 10038299 One Gasket) EGR Adapter to EGR Valve / GM 10038298 Two Gaskets) EGR Tube / GM 10038300
And yes the hole was about the size of a pencil eraser head.
