88 GMC with code 32

[OldBlue_88]

I have a 1988 GMC Sierra 305 with 400 Turbo that on longer drives has the Service Engine Soon light to come on, but almost never on with shorter (5 to 10 mile) drives. Once it does come on it almost always stays on until the engine is shut off. I will say that there really isn’t a noticeable difference in how the truck runs with the light on but still would like to resolve the problem if I can. I have performed the paperclip check and got only one code, a code 32. My search indicates that a code 32 is EGR related, but so far that is all the information I have found. What more do I need to know concerning that code? I currently have the two nuts for the EGR valve soaking in PB Blaster so hopefully I can eventually get the valve removed and checked without causing myself a lot more work. I have noticed that the module that appears to control the vacuum to the EGR valve has another vacuum port on it that is open. Is there supposed to be something attached to that port or should it just be closed off? Any and all assistance is greatly appreciated. Thanks,

 

[DerekTheGreat]

On my '89 Firebird with it's 305, the EGR passages in the intake manifold were plugged solid. I never saw that code again once I swapped on the Edelbrock Performer TBI manifold.

 

[GrimsterGMC]

The EGR system has a self check scenario, where by when a set of parameters are met it will open the valve and look for changes in the O2 readings. If no changes are registered it will set a fault code. It is very common if you have a free flowing exhaust system. This can be because the valve isn't working, the passage is blocked or the exhaust flows to fast and the computer miss times when it should see a change in O2. The self test will generally only happen once you are in closed loop, you are at a cruising speed for a set amount of time without throttle changes etc and this why it only shows on a longer drive.

 

[someotherguy]

It's behaving as expected when there's an EGR system fault. As Grimster mentioned there's a set of parameters to be met before the ECM will run the EGR test. Closed loop, partial throttle, steady-state cruise for a certain amount of time - etc. It's described in the factory service manual. It opens the EGR valve momentarily, then compares before/after readings on the O2 sensor to see if there was a change. If not, set code 32.

One of the ports on the EGR solenoid is normally left "open" - there's a smooth one with no hose barb. That's the vent. Originally there's a small foam filter on them but they fall apart over time.

Diagnostic procedures for code 32 are in the service manual (available for free download here in the forums) - though most likely you'll find the valve itself is bad, or the intake passages completely clogged with carbon. If you end up replacing the valve it can be a little tricky getting the right one. You might consider carefully trying to clean any carbon from the pintle in your existing one and see if it will behave.

Richard

 

[OldBlue_88]

I appreciate everyone’s comments and suggestions. I recently had a serious exhaust leak between the Cat. and the muffler repaired and haven’t driven the truck much distance since then. Could that have been at least part of the problem? Also, I don’t see anything on or near that EGR solenoid that should plug into that second vacuum port on the EGR side of the solenoid. So I’m suspicious that perhaps that could be causing a vacuum leak when the solenoid tried to operate the EGR valve thus causing a malfunction of the EGR system. I assume that might could cause that error code. What does everyone think of that possibility? Thanks,

 

[Schurkey]

I recently had a serious exhaust leak between the Cat. and the muffler repaired and haven’t driven the truck much distance since then. Could that have been at least part of the problem?

Seems unlikely.

I don’t see anything on or near that EGR solenoid that should plug into that second vacuum port on the EGR side of the solenoid. So I’m suspicious that perhaps that could be causing a vacuum leak when the solenoid tried to operate the EGR valve thus causing a malfunction of the EGR system. I assume that might could cause that error code. What does everyone think of that possibility?

That second "nipple" has no hose barbs. IT'S A VENT. It's SUPPOSED to be open to atmosphere--although ideally there'd be a foam filter on it. As has already been said--the foam filters disintegrate over time leaving the nipple bare-naked.

 

[OldBlue_88]

Schurkey; Ok, yeah thanks. I somehow missed someotherguy’s second paragraph regarding that second port being open. Tomorrow I’ll do some more checking to see if I can determine what is wrong with the EGE system. Thanks to everyone.

 

[OldBlue_88]

Went out this morning and did manage to get the EGR valve off without in problems. I tested the solenoid with 12 volts and it clicked so I assume it is functioning properly. I tested the solenoid plug for volts but did not detect any voltage by just turning the key on. Based on everyone’s description of when the solenoid usually operates I didn’t really expect to see any voltage but decided to make the test anyway. I did attempt to test out the EGR valve itself. I hooked it up to a good valcuum source on another vehicle and could not detect any movement. I could actually suck on a hose connected to the EGR and draw air, very much restricted but I could get air. Does it sound like the EGR valve is most likely the source of my problem? I would appreciate everyone’s thoughts on what I have determined so far with my testing. Is there other tests I should make before I get a replacement EGR valve? Thanks,

 

[GrimsterGMC]

Went out this morning and did manage to get the EGR valve off without in problems. I tested the solenoid with 12 volts and it clicked so I assume it is functioning properly. I tested the solenoid plug for volts but did not detect any voltage by just turning the key on. Based on everyone’s description of when the solenoid usually operates I didn’t really expect to see any voltage but decided to make the test anyway. I did attempt to test out the EGR valve itself. I hooked it up to a good valcuum source on another vehicle and could not detect any movement. I could actually suck on a hose connected to the EGR and draw air, very much restricted but I could get air. Does it sound like the EGR valve is most likely the source of my problem? I would appreciate everyone’s thoughts on what I have determined so far with my testing. Is there other tests I should make before I get a replacement EGR valve? Thanks,

It's quite common for the diaphragm to fail. Just make sure you get the correct replacement as there are 2 different types for these trucks and they operate the opposite way to each other.

 

[Schurkey]

EGR valve is shot based on your testing--inability to hold vacuum. Being a TBI, you almost certainly have a negative-backpressure EGR valve, the OEM valve will have an "N" stamped into it near the part number. An aftermarket valve may or may not have the "N" stamped into it. As said, be sure to get the correct one.

If the old valve has a restricted vacuum nipple, be sure the new one does, too. Otherwise you need to slice of the restricted part of the nipple, apply some grease, and cram it down the vacuum hose ahead of the new, non-restricted EGR valve. (Of course, the best plan is to simply buy a proper replacement instead of kludging a "fix" for the incorrect valve.)

EGR solenoid clicks, but does not mean it will pass air. Put power to it so it clicks--and see if the solenoid valve opens so that air can be drawn through from where the two vacuum hoses connect. When power is removed, air should be able to be drawn through from the EGR vacuum hose to the vent nipple.