93 5.7 EGR question
 

On my 93 1/2 ton with 5.7 TBI I'm still getting a code 32 for the EGR. The check engine light doesn't come on every trip, but when it does it's always at light throttle at highway speeds. I've replaced the EGR vacuum solenoid. To get an idea of what is happening to throw the light I teed in a vacuum gauge between the solenoid and EGR valve have an indicator light wired into the solenoid. What I've found out is less than a second before the check engine light comes on the solenoid indicator light will blink off for a split second. Before the vacuum can even drop to 0 the indicator is back on. It's done this each time the check engine light has come on. Is this telling me the problem is either in the wiring or ECM instead of the EGR? It doesn't cause it to run bad, I just hate a check engine light. Thanks for any info.

Re: 93 5.7 EGR question
 

This should help you, read all the posts...

https://www.chevytalk.org/fusionbb/s...hp?tid/258416/

Re: 93 5.7 EGR question
 

I am the same ChevyTech that is in that thread that EVRLET posted a link to. Use the tests in that thread to get as far as you can and then ask questions here and I will try to walk you through it.

The first test I would suggest is to put a hand vacuum pump on the EGR valve and see if it will open with the engine off.

Re: 93 5.7 EGR question
 

Evrlet and ChevyTech, I wanted to let you know I hadn't forgotten or just blew you off or something. The flu pretty much tore me up and just now getting my legs back under me. It seems like the EGR valve was sticky. Sometimes when I pumped it up it would hold vacuum, sometimes it wouldn't. I put a new one on and drove it and so far no code. I think you guys healed it. Thanks for the help. And also thanks for uploading the service manuals that you did. They are so much more help than the Chiltons or Haines manuals. It seems like they only want tell you how to open the door and where the tires are located. Thanks again.

Re: 93 5.7 EGR question
 

You're welcome.

That EGR valve should hold vacuum with the engine off, but with the engine running it will bleed off the vacuum as soon as a puff of pressure is in the exhaust.

Let us know if the problem returns.

Re: 93 5.7 EGR question
 

I sure will. I do have another question if you don't mind. I've had this truck for almost 10 years. It has an O2 sensor in the left exhaust manifold but it hasn't been hooked up since before I bought it. I can't even find anything to plug it into. Without it is the ECM just guessing what changes to make? It's always surprised me it hasn't thrown a code.
Thanks again, Randy

Re: 93 5.7 EGR question
 

In 1993 the oxygen sensor is in the divers side exhaust manifold, near the flange.

If the oxygen sensor is not connected it should set a trouble code. Make sure the light comes on when you turn the key before cranking the engine. Somebody may have put in a custom chip that is preventing a code from being set.

To set the code 32 the system cuts the EGR operation under specific criteria and watches the oxygen sensor expecting a change which meets a threshold.

A vehicle without an oxygen sensor will run in the “Open Loop” mode and will get an amount of fuel that is in the program in the PROM(chip) that is what should be adequate if the other sensors are working OK and everything is about where it should be.

You will not get the best fuel economy or performance running in open loop with no oxygen sensor connected to the system.