Egr Help

studibel · November 21, 2009

I have a 93 suburban. Just changed the distributor and all seems to be fine. However, I still am idling about 1100-1200. When I pull down into drive, it will idle down to about 900.

When the motor warms up, "Check Engine Light" will come on. I can check the code and get 35 Idle Air Control. I've changed this IAC motor but still getting CEL. Also I've noticed that when engine is warm, at idle can get a high pitched whistle indicating vacuum leaking from the EGR valve. I can push up the valve diaphragm and make the whistle stop, so I can assume EGR valve is leaking vacuum. Will this or can this cause the code 35 IAC which then causes the CEL light to come on? Will or can this vacuum leak cause my high idle condition? Code 32 is the EGR valve DTC but I don't get a 32 code...just 35. Do I just go change the EGR and see if that fixes it?

HELP??

Nytemare · November 21, 2009

Pull the vacuum hose off the EGR and plug it. That is all you have to do to test it.

That is assuming you have the Top-Hat style EGR (looks like a top-hat)

studibel · November 21, 2009

Pull the vacuum hose off the EGR and plug it. That is all you have to do to test it.

That is assuming you have the Top-Hat style EGR (looks like a top-hat)

Forgive the dumb question...but, just plug the EGR vacuum hose? Will that lower the engine RPM at idle? I've tried removing the vacuum hose and it doesn't change idle speed at all. Do I just need to plug it as you say and then run it for a while?

I've sprayed carb cleaner around the TBI to check for other vacuum leaks and I don't see or hear anything. I think it is related to either this EGR leak or Idle Air control...but that's new...frustrating!

Nytemare · November 21, 2009

The hose that connects to the EGR is a vacuum line. If you don't plug it its still a vacuum leak.

Its that hose that supplies vacuum to and moves the diaphragm of the EGR up and down dependent on engine vacuum...(vacuum changes with engine speed).

I don't know if its actually your EGR that's causing your troubles...but its something I always try before going further into the trouble shooting procedure. A lot of the time it works.

studibel · November 21, 2009

The hose that connects to the EGR is a vacuum line. If you don't plug it its still a vacuum leak.

Its that hose that supplies vacuum to and moves the diaphragm of the EGR up and down dependent on engine vacuum...(vacuum changes with engine speed).

I don't know if its actually your EGR that's causing your troubles...but its something I always try before going further into the trouble shooting procedure. A lot of the time it works.

I will give it a try. Looks like a golf tee or something similar might be the right size for that vacuum line. At a minimum, having no vacuum to the EGR will stop that high pitched whistle that I can hear sometimes after the engine warms up (only at idle though). I think as you accelerate, the vacuum leak must stop as it activates the EGR diaphragm.

One other question. I borrowed a friend's Matco MD2100 ScanTool but I found out it only scans 1994 and newer and mine's a 93. So, that wouldn't work. One of the reasons I wanted to use it was to completely "blow out" any stored codes in the computer which this tool supposedly can do. Since I can't do that with the tool, if I disconnect the neg battery cable, does that actually remove all codes? I assume I would need to do this BEFORE I try this EGR test so that I will know if I get a new EGR code? I've been told that just disconnecting the negative will only reset the Check Engine Light but won't actually remove the codes.

By the way, thanks for helping!

minibike132 · November 21, 2009

Remove both cables and hold them togeather for a few seconds.

studibel · November 21, 2009

Remove both cables and hold them togeather for a few seconds.

That will completely remove codes from the computer?

minibike132 · November 21, 2009

Remove both cables and hold them togeather for a few seconds.

That will completely remove codes from the computer?

Yep

Nytemare · November 21, 2009

The hose that connects to the EGR is a vacuum line. If you don't plug it its still a vacuum leak.

Its that hose that supplies vacuum to and moves the diaphragm of the EGR up and down dependent on engine vacuum...(vacuum changes with engine speed).

I don't know if its actually your EGR that's causing your troubles...but its something I always try before going further into the trouble shooting procedure. A lot of the time it works.

I will give it a try. Looks like a golf tee or something similar might be the right size for that vacuum line. At a minimum, having no vacuum to the EGR will stop that high pitched whistle that I can hear sometimes after the engine warms up (only at idle though). I think as you accelerate, the vacuum leak must stop as it activates the EGR diaphragm.

One other question. I borrowed a friend's Matco MD2100 ScanTool but I found out it only scans 1994 and newer and mine's a 93. So, that wouldn't work. One of the reasons I wanted to use it was to completely "blow out" any stored codes in the computer which this tool supposedly can do. Since I can't do that with the tool, if I disconnect the neg battery cable, does that actually remove all codes? I assume I would need to do this BEFORE I try this EGR test so that I will know if I get a new EGR code? I've been told that just disconnecting the negative will only reset the Check Engine Light but won't actually remove the codes.

By the way, thanks for helping!

The whistle goes away as you accelerate due to higher RPM's means less vacuum. The diaphragm actually moves down at higher speeds.

A golf tee or a bolt, I have used ball bearings for a permanent plug. But the golf tee will do for a check.

you are supposed to disconnect the positive terminal to erase codes...but I find a full disconnect and touching the leads together for a few seconds like Spark said is the best.

alwcurlz · November 23, 2009

Positive lead or Negative lead? It doesn't matter which wire is removed...but, touching the cables together to clear the PCM? Yikes. I've usually just disconnected a power lead, (usually the negative one in case the wrench being used to loosen the terminal touched ground somewhere) and let it set for about 30 min and re-connect.

studibel · November 23, 2009

Positive lead or Negative lead? It doesn't matter which wire is removed...but, touching the cables together to clear the PCM? Yikes. I've usually just disconnected a power lead, (usually the negative one in case the wrench being used to loosen the terminal touched ground somewhere) and let it set for about 30 min and re-connect.

You have raised a concern I had about doing this. I've read other places that touching the neg/pos leads can do damage to the computer, which is the LAST thing I want to do right now! I would like to get a fresh start but I am not sure how to clear the codes from the computer...short of taking it somewhere with a scantool that can go back to 93. You said leave it unhooked for 30 minutes or more...will that actually clear the PCM?

Nytemare · November 23, 2009

I have been touching both leads together for years man...never hurt an ECM yet...but you have to make sure both leads are dis-connected for this. If you are uneasy about it...just do what adber said...disconnect and leave it alone for 30min. disconnect both if you're unsure.

From everything I have been told by the techs at GM though...its the positive lead that has to be taken off for best results of clearing codes, without using a scan tool. If you're scared you will ground out...disconnect both, neg first.

Do this to clear the codes...unplug the EGR vacuum line and cap it with a golf-tee and see what happens. Your throwing a IAC code because the idle is not falling to normal after the allotted time, so the ECM thinks that the IAC is not returning to normal position.

alwcurlz · November 24, 2009

Positive lead or Negative lead? It doesn't matter which wire is removed...but, touching the cables together to clear the PCM? Yikes. I've usually just disconnected a power lead, (usually the negative one in case the wrench being used to loosen the terminal touched ground somewhere) and let it set for about 30 min and re-connect.

You have raised a concern I had about doing this. I've read other places that touching the neg/pos leads can do damage to the computer, which is the LAST thing I want to do right now! I would like to get a fresh start but I am not sure how to clear the codes from the computer...short of taking it somewhere with a scantool that can go back to 93. You said leave it unhooked for 30 minutes or more...will that actually clear the PCM?

Yeah, and also jump-starting someone else's vehicle can cause damage to some PCMs. If you disconnect a power lead to the computer, it'll clear the codes after some time. You could disconnect it before the evening and in the morning hook it back up to make sure it's cleared.

On the other test you tried, spraying carb cleaner into a vacuum leak on an injection system won't do much of anything except make it choke and stall if you get enough in there, and the PCM will adjust the fuel rate. On that EGR valve, are you sure it's a vacuum leak there? The EGR gets pretty caked up easily over time and could be causing a restriction and that whistle. That would also possibly cause the idle air control to reach it's limit, giving you an error code. Could you give a little more history on this issue? Like, did you just buy the truck?, how long has it been doing this? When did it start? How many miles on it? One thing that you could do on that EGR valve is take it out and clean it up with carb cleaner. Spray a cup full of the cleaner and let it soak. The EGR makes a big difference in how the engine runs. Clean it or replace it. It'll be around $70 for an EGR valve to replace it. Don't forget to get a gasket because that soft metal gasket for the EGR is a one time use gasket.

I had a 1994 Silverado with similar problems not related the same way but, cleaned it too.

Good luck!

studibel · November 24, 2009

Positive lead or Negative lead? It doesn't matter which wire is removed...but, touching the cables together to clear the PCM? Yikes. I've usually just disconnected a power lead, (usually the negative one in case the wrench being used to loosen the terminal touched ground somewhere) and let it set for about 30 min and re-connect.

You have raised a concern I had about doing this. I've read other places that touching the neg/pos leads can do damage to the computer, which is the LAST thing I want to do right now! I would like to get a fresh start but I am not sure how to clear the codes from the computer...short of taking it somewhere with a scantool that can go back to 93. You said leave it unhooked for 30 minutes or more...will that actually clear the PCM?

Yeah, and also jump-starting someone else's vehicle can cause damage to some PCMs. If you disconnect a power lead to the computer, it'll clear the codes after some time. You could disconnect it before the evening and in the morning hook it back up to make sure it's cleared.

On the other test you tried, spraying carb cleaner into a vacuum leak on an injection system won't do much of anything except make it choke and stall if you get enough in there, and the PCM will adjust the fuel rate. On that EGR valve, are you sure it's a vacuum leak there? The EGR gets pretty caked up easily over time and could be causing a restriction and that whistle. That would also possibly cause the idle air control to reach it's limit, giving you an error code. Could you give a little more history on this issue? Like, did you just buy the truck?, how long has it been doing this? When did it start? How many miles on it? One thing that you could do on that EGR valve is take it out and clean it up with carb cleaner. Spray a cup full of the cleaner and let it soak. The EGR makes a big difference in how the engine runs. Clean it or replace it. It'll be around $70 for an EGR valve to replace it. Don't forget to get a gasket because that soft metal gasket for the EGR is a one time use gasket.

I had a 1994 Silverado with similar problems not related the same way but, cleaned it too.

Good luck!

It has been idling fast for a little while. I've owned the truck since 2000. It has 200,000+ miles on it. Bought it with 97,000 miles in 1/2000. I just replaced the distributor as I had issues with the ignition module/pickup coil. That repair fixed those ignition issues but didn't fix any fast idle issues. I have replaced the IAC which did nothing to help. I have replaced the PCV and the vacuum tube from TBI to it. I haven't replaced that EGR yet. The vacuum whistle started after I replaced the distributor and doesn't do it all the time. I thought maybe I broke a vacuum line/connection while crawling around fixing the distributor. But, found the EGR valve was the culprit. When I hear it, I can push the diaphragm up a bit and it goes away. At idle, when it is warmed up, it will whistle, but then throttle up and it goes away...and not every time either. It seems like it is trying to idle down a little. When pulling up to a stop light with foot on the brake, it will idle down to about 900 or so. The throttle seems very smooth. Just not sure how to fix the fast idle and the codes 32 and 35. I have pulled and plugged the vacuum line from EGR to see if it will produce the code...idle is still fast. I removed the neg cable yesterday, but probably not long enough. I will do that today and let it sit for a while. Sounds like I need to remove both battery cables to make sure the ECM is cleared of all codes. Maybe all of this isn't that big a deal. I don't think the fast idle is hurting anything. Maybe just replacing or at least cleaning the EGR valve might produce some effect. And the Check Engine codes 32 and 35...not sure it is doing anything else than just being an annoyance.

I appreciate the help...thanks for sharing your knowledge!

studibel · November 24, 2009

I have been touching both leads together for years man...never hurt an ECM yet...but you have to make sure both leads are dis-connected for this. If you are uneasy about it...just do what adber said...disconnect and leave it alone for 30min. disconnect both if you're unsure.

From everything I have been told by the techs at GM though...its the positive lead that has to be taken off for best results of clearing codes, without using a scan tool. If you're scared you will ground out...disconnect both, neg first.

Do this to clear the codes...unplug the EGR vacuum line and cap it with a golf-tee and see what happens. Your throwing a IAC code because the idle is not falling to normal after the allotted time, so the ECM thinks that the IAC is not returning to normal position.

I do trust that you know what you're talking about! I probably read too much...I know I've read other posts elsewhere that says touching the +/- leads can cause damage. I did cap off the vacuum line with a golf tee after removing the neg lead yesterday. I'm confident that I didn't leave it disconnected long enough. And, it was just the neg...will remove both today and let it sit for a while to make sure.

Thanks a lot for your help! I appreciate your willingness to help me out. I posted some other details on Adber's post.