Stumbling when put in gear?

[1500z71]

Hey guys I finally got back around to this and tried pressing on the EGR. The whole problem has gotten worse now in the sense of it wants to stumble at idle in all gears.

With it on and stumbling, I depressed the EGR and the idle did get immediately worse. However - after I let it go, no more stumble. After a few minutes of a perfect idle, had someone put it in drive and hold the brake and the stumble started again, but same thing - depressed and released the EGR and no more stumble, not even back in park. So we definitely have something, just not sure how to interpret it.

 

[HawkDsl]

Hey guys I finally got back around to this and tried pressing on the EGR. The whole problem has gotten worse now in the sense of it wants to stumble at idle in all gears.

With it on and stumbling, I depressed the EGR and the idle did get immediately worse. However - after I let it go, no more stumble. After a few minutes of a perfect idle, had someone put it in drive and hold the brake and the stumble started again, but same thing - depressed and released the EGR and no more stumble, not even back in park. So we definitely have something, just not sure how to interpret it.

EGR's are cheap. Call 1-800-replace-it.com.gov.info

 

[1500z71]

EGR's are cheap. Call 1-800-replace-it.com.gov.info

10/4. Just making sure that was indicating a failing EGR

 

[Schurkey]

Hey guys I finally got back around to this and tried pressing on the EGR... ...I depressed the EGR

Define "depressed".

On my truck, I'd call it "lifting" the diaphragm with fingertips, which then lifts the pintle off of it's seat, which allows exhaust gas to flow into the intake air/fuel stream.

and the idle did get immediately worse. However - after I let it go, no more stumble. After a few minutes of a perfect idle, had someone put it in drive and hold the brake and the stumble started again, but same thing - depressed and released the EGR and no more stumble, not even back in park. So we definitely have something, just not sure how to interpret it.

Remove the vacuum hose from the EGR valve nipple, connect a vacuum gauge. The vacuum gauge should show NO vacuum at idle. Make sure it doesn't build vacuum as time goes by--let it idle for a few minutes with the gauge connected.

If you open the throttle, you might see vacuum on the gauge, but it must drop to zero when the throttle is released. If it doesn't drop to zero, the EGR solenoid is faulty, or the vacuum-bleed (covered with a filter sponge when new, but the sponge deteriorates and falls-off with age) is plugged.

Very slight chance that the vacuum hose between throttle body and EGR solenoid is connected to the wrong nipple on the throttle body. The solenoid should have no vacuum when the throttle is at idle, or even a little above idle.

 

[1500z71]

Define "depressed".

On my truck, I'd call it "lifting" the diaphragm with fingertips, which then lifts the pintle off of it's seat, which allows exhaust gas to flow into the intake air/fuel stream.


Remove the vacuum hose from the EGR valve nipple, connect a vacuum gauge. The vacuum gauge should show NO vacuum at idle. Make sure it doesn't build vacuum as time goes by--let it idle for a few minutes with the gauge connected.

If you open the throttle, you might see vacuum on the gauge, but it must drop to zero when the throttle is released. If it doesn't drop to zero, the EGR solenoid is faulty, or the vacuum-bleed (covered with a filter sponge when new, but the sponge deteriorates and falls-off with age) is plugged.

Very slight chance that the vacuum hose between throttle body and EGR solenoid is connected to the wrong nipple on the throttle body. The solenoid should have no vacuum when the throttle is at idle, or even a little above idle.

Exactly how you described it. I was saying depressed but was talking about lifting, I understand now.

I’ll try to pick up a vacuum gauge tomorrow.

 

[1500z71]

Well I went to swap the EGR tonight with a factory one that I know works and darn if I didn’t bust a couple vacuum lines getting it out. Busted the line from the back of the throttle to the MAP and the EGR to the solenoid. Might’ve been the problem all along. So tomorrow I’m going to get new lines and I am gonna go ahead and just get a new EGR since I’m already in there.

Do y’all just get a roll of matching hose or do you try to get the actual part? Do y’all reuse the boots?

 

[HawkDsl]

<snip>
Do y’all just get a roll of matching hose or do you try to get the actual part? Do y’all reuse the boots?

I just bought the hard line roll, and using a heat gun, bent up new line. If the original boots are good, use 'em. GM's OEM boots are by far better then anything your going to find at the Parts store.

 

[Schurkey]

I splice the original pieces together using short sections of vacuum hose. Simple, cheap, easy.

I like the idea of buying a roll of tubing, and using a heat-gun to form it, though.

 

[1500z71]

I just bought the hard line roll, and using a heat gun, bent up new line. If the original boots are good, use 'em. GM's OEM boots are by far better then anything your going to find at the Parts store.

Only one bad 90 degree boot. The rest are in good shape. The boot for the MAP line that is on the back of the throttle seems like it has welded itself on there over the years so it gets to stay there...

 

[1500z71]

Man fellas I am chasing this thing down and I am so close. Alright, so here’s what I did tonight and how it went:

Replaced EGR valve, replaced the line from valve to solenoid and kept the factory boots. Replace the line from the throttle to the MAP and added a new elbow. Started it up and it did not miss a beat in Park, idled perfect. Still stumbled just as hard in gear - but it would catch itself much quicker and idle normal.

Went back in and replaced the line from the EGR solenoid to the front of the throttle with factory boots (it had a splice in it). Only stumbled for just a second or two and would catch, even quicker than the first time.

Last thing I did after that was went back in and deleted the autozone elbow from the throttle to the MAP and ran it direct with a new line. After that - it ran perfect through all gears, absolutely factory. No stumble or anything. At least for a few cycles through the gears, and then the stumble started again, albeit still much much better than how it was, and it wasn’t as consistent. Sometimes will, sometimes won’t, but will still catch itself.

The only thing that I have not laid my eyes on is the factory boot on the back of the throttle. I couldn’t get it off and I’m worried I could’ve possibly torn it when I was trying. Other than, all boots and lines look good. I suppose somewhere the connection could be loose, but I’m not sure.

Video is up. This was before I deleted the elbow and replaced the solenoid to throttle line, which almost completely got rid of the stumble.

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I assume I am still on the right path and not missing something. Any thoughts on where to go next?