87-95 TBI EGR code 32

[jameslleary]

Hi guys,
I was not sure exactly where to post this, so I will stick it here, and the Mods can move it as they see fit.
This post is intended for anyone in my situation, where they have to pass emissions tests, and have swapped in a GM TBI system.
Since I have decided to stay with TBI, i have been chasing down a problem with the EGR system, throwing code 32.
Today I found the problem.
I am still running the dual cat exhaust, with magnaflow mufflers inline, and dual 2" tailpipes, like what came on the 86 trucks from the factory.
This exhaust configuration is entirely too free flowing for the TBI EGR system to work properly, as this particular EGR system is disigned to operate with the help of back pressure from the original single cat ehaust system, found on un-molested 87-95 GM light Trucks.
I have cured the problem by stuffing one of the tailpipes with tightly rolled shop rags....no code 32.
I have confirmed this by removing the rags, and then driving at 55 mph, and code 32 comes back up, when pressing on the accellerator to maintain speed.

[EagleMark]

Code 32 is a PIA sometimes to cure and your test and cure here is awesome!

But I don't think it was because of back pressure needed for EGR, I think you changed something to increase or decrease engine vacuum to put it in boundries of test. Either way you found a cure and with this finding we may be able to make a simple change in bin file so EGR test can occur and pass with changed engine vacuum because of free flowing exhaust...

Here read the GM manaul for Code 32 and you'll understand what I am saying... the complete TBI manual in pdf can be found bottom of this post.
http://www.gearhead-efi.com/Fuel-Inj...-CEL-SES-Light

[jameslleary]

Thats an ok idea, only problem is, the TBI EGR valves will not work solely on vacuum, like the TPI, and earlier carbed EGR valves do.
I dont know if this is true with TBI fuel cars, but the truck valves act as if they have a metered leak in them, which requires sme exhaust pressure to help it out...I dont know what GM engineers wer thinking when they decided to make it this way...but they did.

[EagleMark]

When EGR opens it's passage is to engine vacuum (vacuum drops for test) so it sucks a little exhaust in.... I've never heard or read anything about EGR operation that mentions exhaust pressure? But you have obviously proved something here with code 32, but code 32 tests for MAP reading. And it's only a test when the 3 qualifiers mentioned above are met? Not that the EGR has failed...

So I looked in the $42 hack, then $42-1227747-V3.xdf and sure enough, there it is, first one in Flags. "Options @ 0x0005 - Bit 7 - EGR" Checked! Uncheck it and test is off, no more code 32 with free flowing exhaust.

[jameslleary]

Yeah, but they pull the plug on the egr solenoid here to make sure it throws a code during bi annual inspection.

[EagleMark]

That would set a differant code, I think. What mask?

EDIT: On $42 I was talking about would turn off the bit for the test, not the error code after test failed! So code 32 would still work, but won't because the test would never happen. Not sure but if you pull the wire off EGR it should set a code.

Or have 2 chips. One stock for inspection one with Code 32 test off? Besides other cool stuff...

[jim_in_dorris]

James, is that a P or N EGR? And my smog guy just told me yesterday that if your vehicle came with single exhaust, that dual exhaust even with 2 cats will be an automatic fail next year. I have true duals with 2 1/2 " pipes on my 87 with cats, and don't throw an EGR code.

[jameslleary]

I was thinking 2 chips as well, i would like to get a chip with your hwy mode.
Jim, the truck had TPI, CA certified with dual cats, i will be changing it to a single cat system...Yup, its me, from FSC.

[jameslleary]

p or n?

[EagleMark]

I was thinking 2 chips as well, i would like to get a chip with your hwy mode.

I just revived it, RBob is the one to credit!

[jim_in_dorris]

There are 2 types of EGR valves. TBI uses a Negative pressure EGR, and has an N in the part #. Using a P (Positive) part number will cause EGR codes and other strange behavior.

Yeah I figured it was you... What are you switching from TPI to TBI?

[93V8S10]

I wounder if the coding could be changed to work with the P valve. This would depend upon whether the P and N valves look similar or not. Would have to get a replacement P valve and write in the old N valve part number. Of coarse all of this would be pointless if it's an automatic fail with duels.

I'm not sure, but I believe that the $0D code will run P, N, and Digital if set-up correctly. Don't know about $42 though.

[jameslleary]

Yep, The Burb has become more of a family cruiser now, and i just wanted to go with something reliable, that i can work on easily on the road if I have to. If i get another project truck, I want to maybe get a 73-74 longbed with a 292 I6, and do something multiport to it. I went by the oem info that i was able to find for the system I am using, and matched up the correct orofice that came with the Egr valve. I am thinking that i may need to cange the solenoid, as i am still using the one from the TPI.

[EagleMark]

Thats an ok idea, only problem is, the TBI EGR valves will not work solely on vacuum, like the TPI, and earlier carbed EGR valves do.
I dont know if this is true with TBI fuel cars, but the truck valves act as if they have a metered leak in them, which requires sme exhaust pressure to help it out...I dont know what GM engineers wer thinking when they decided to make it this way...but they did.

There are 2 types of EGR valves. TBI uses a Negative pressure EGR, and has an N in the part #. Using a P (Positive) part number will cause EGR codes and other strange behavior.

Ahhh! That's what he was talking about in above quote? I hadn't realized there were 2 kinds... this would explain a lot of Code 32 issues!

[EagleMark]

I wounder if the coding could be changed to work with the P valve. This would depend upon whether the P and N valves look similar or not. Would have to get a replacement P valve and write in the old N valve part number. Of coarse all of this would be pointless if it's an automatic fail with duels.

I'm not sure, but I believe that the $0D code will run P, N, and Digital if set-up correctly. Don't know about $42 though.

We are lucky to have a very nicely written $42.xdf by Robert Saar that has many, many more options then others I have seen, probably 3-4 times as many parameters then TunerCat. Lots of EGR settings.

But it may not be a scaler or table. But in bitmasks we have:
Options @ 0x0005 - Bit 7 - EGR which I believe would turn off Code 32 test! Not the Code 32 error code.

Then these 2 I do not know what they are for?
Options @ 0x0005 - Bit 4 - EGRIN = Not checked
Options @ 0x0005 - Bit 3 - EGRDC = Checked