Rough idle - vacuum

[Tac Map Mike]

I’m chasing a terribly rough idle. 1991 5.7 tbi 2wd. New plugs, wires, cap, and rotor. Was going to pull the Egr off to clean and or replace it. I noticed there is a line going to the Egr and then an open hole where there should be a vacuum line? Where does it go and could this cause my rough idle

You must be registered for see images attach

 

[PlayingWithTBI]

I noticed there is a line going to the Egr and then an open hole where there should be a vacuum line? Where does it go and could this cause my rough idle

Nope, that's the vent port for the EGR control module.

 

[Tac Map Mike]

Nope, that's the vent port for the EGR control module.

Ok gotcha. Thanks!

 

[Tac Map Mike]

Can I try capping the line going to the EGR? Or is that not gonna work to troubleshoot?

 

[PlayingWithTBI]

Can I try capping the line going to the EGR? Or is that not gonna work to troubleshoot?

If the EGR and/or module is bad, capping the line won't do anything for you.

 

[Schurkey]

The "open hole" on the EGR Solenoid is supposed to have a crappy foam filter on it. After this many years, none of 'em do any more.

There shouldn't be any vacuum in the EGR system at idle. But maybe the vacuum hose at the throttle body is connected to the wrong nipple. No harm in unplugging the valve and blocking the hose for testing purposes. PROPERLY testing the EGR system will be more-involved than just disconnecting the hose, though.

What is the cranking compression of all eight?
Have you tried a cylinder-balance test to identify the problem cylinder(s)?
Did the plug wires get put on the correct spark-plugs?
What is the fuel pressure?
Connect a scan tool, look for codes, verify ALL the sensors and computer outputs.

 

[Tac Map Mike]

The "open hole" on the EGR Solenoid is supposed to have a crappy foam filter on it. After this many years, none of 'em do any more.

There shouldn't be any vacuum in the EGR system at idle. But maybe the vacuum hose at the throttle body is connected to the wrong nipple. No harm in unplugging the valve and blocking the hose for testing purposes. PROPERLY testing the EGR system will be more-involved than just disconnecting the hose, though.

What is the cranking compression of all eight?
Have you tried a cylinder-balance test to identify the problem cylinder(s)?
Did the plug wires get put on the correct spark-plugs?
What is the fuel pressure?
Connect a scan tool, look for codes, verify ALL the sensors and computer outputs.

I’ve sprayed carb cleaner on all the vacuum lines I can see to no avail. I did forget to check the canister. Wires are correct. Not sure of the fuel pressure or the compression. I tried hooking up a rented scan tool but it wouldn’t communicate (though no engine codes). I’ve just been driving it as it’s my beater but I wouldn't mind figuring it out. It’s very possible it’s low compression or the fuel pump taking a hike, though it never stalls and runs really well in the city when rpm’s are up.

I took the EGR valve off and cleaned it up as good as I could. Didn’t feel the the spring was broken.

I do occasionally hear this super loud whining sound in park when warm - seemed to go away when i
Sprayed the EGR with carb cleaner lol

 

[2drXmobb]

Smoke test, you can make a jug and wick if you don't have the tools, it's the best way to find a vacuum leak , or old-school and spray carb cleaner on the hoses but that'***** and miss

 

[tsr2185]

I’m chasing a terribly rough idle. 1991 5.7 tbi 2wd. New plugs, wires, cap, and rotor. Was going to pull the Egr off to clean and or replace it. I noticed there is a line going to the Egr and then an open hole where there should be a vacuum line? Where does it go and could this cause my rough idle

You must be registered for see images attach

ever figure out your problem?

 

[Kajunchevy]

I’m chasing a terribly rough idle. 1991 5.7 tbi 2wd. New plugs, wires, cap, and rotor. Was going to pull the Egr off to clean and or replace it. I noticed there is a line going to the Egr and then an open hole where there should be a vacuum line? Where does it go and could this cause my rough idle

I’m chasing a terribly rough idle. 1991 5.7 tbi 2wd. New plugs, wires, cap, and rotor. Was going to pull the Egr off to clean and or replace it. I noticed there is a line going to the Egr and then an open hole where there should be a vacuum line? Where does it go and could this cause my rough idle

You must be registered for see images attach

I'm sorry I don't have any answer but am curious what this is that I circled. I have a 95 5.7 tbi and have vacuum issues myself possibly due to the person who had the truck before be trying to so call delete things and took alot off.