No vacuum to EGR? (1 Viewer)

[thestunts]

Went in for smog today. Everything passed but the gas cap, EGR functional test & timing (was at 11). Luckily everything else including the sniffer test passed.

They said the EGR has no vacuum.

Would this be a result of a bad VSV? Bad EGR? Vacuum modulator?

Thanks in advance!
P.S. I did the head gasket awhile back and replaced all the vacuum tubes then, so those should be good.

**edit**

 

[Schwaz80]

FSM has test procedures for the EGR system. It could be any one of those items you listed. Track down an FSM and go from there

 

[Splangy]

How did they test for vacuum? If it truly isn't getting vacuum, then it must be the modulator, a clogged EGR port in the throttle body, or a bad vacuum hose(s). I have a feeling that they probably didn't test for vacuum to the EGR valve correctly, though. Go through the test procedures in the FSM.


The vacuum signal doesn't come from the VSV. The VSV closes off one end of the system so that the signal from the modulator will pull the EGR valve open.

 

[thestunts]

Quick update & looking for any tips.
Replaced the vacuum modulator as it was the original from 94 after 290k and it was gunky as crap. Replaced a few vac lines on top because I found a few that had some minor rips/bulges.

Now the nipple off the intake manifold to EGR has no vacuum at idle. I'm assuming it should & I'm assuming its blocked.

Is there an easy way to clean it without removal? - Was able to get a paperclip down in there but then it stops... does that line bend? or am I hitting gunk?

Thanks in advance.

 

[DSRTRDR]

 

[thestunts]

Liking the heart !

No worry of the fuzzies going in there i imagine? Have a few laying around that I'll give a go a little later and report back.

P.S. Is it safe to spray a little carb cleaner in there to "soak".

 

[alia176]

Quick update & looking for any tips.
Replaced the vacuum modulator as it was the original from 94 after 290k and it was gunky as crap. Replaced a few vac lines on top because I found a few that had some minor rips/bulges.

Now the nipple off the intake manifold to EGR has no vacuum at idle. I'm assuming it should & I'm assuming its blocked.

Is there an easy way to clean it without removal? - Was able to get a paperclip down in there but then it stops... does that line bend? or am I hitting gunk?

Thanks in advance.

Can you take a pic of this nipple? Is this the nipple on the driver side of the intake manifold, on the top? If so, this thing goes all the way through the manifold to the other side, down below. You can bypass this thing with a long vac hose if you needed to. But, it should be cleaned if it's clogged.

 

[Rallyroo]

I just did the smog on my 1994 two weeks ago. Same thing, passed emissions with flying colors, but failed in the fuel cap pressure test and EGR function test. I replaced the fuel cap and replaced the EGR modulator valve and passed smog in the free retest.

 

[DSRTRDR]

No worry of the fuzzies going in there i imagine?

the carbon residue gums them up on the wire

 

[thestunts]

Can you take a pic of this nipple? Is this the nipple on the driver side of the intake manifold, on the top? If so, this thing goes all the way through the manifold to the other side, down below. You can bypass this thing with a long vac hose if you needed to. But, it should be cleaned if it's clogged.

At work, but the nipple is on the driver side of the intake manifold near the rear/firewall. The hose literally goes from the nip to EGR in about 5-6 inches of hose....

Does anyone know if it's suppose to have VAC at all times or only at certain RPMS?

P.S. Where does it connect on other side? I might bypass it temporarily ...

 

[Rallyroo]

Does anyone know if it's suppose to have VAC at all times or only at certain RPMS?

Welp, when the smog guy tested the EGR he said the vacuum pressure should go up with RPM. Mine registered zero so it failed. Bought a new EGR modulator valve, came back the next day, free smog retest and passed.

 

[alia176]

At work, but the nipple is on the driver side of the intake manifold near the rear/firewall. The hose literally goes from the nip to EGR in about 5-6 inches of hose....

Does anyone know if it's suppose to have VAC at all times or only at certain RPMS?

P.S. Where does it connect on other side? I might bypass it temporarily ...

Regarding your question about vacuum presence, someone posted up FSM info on this subject so do a search and it should come up. I think the VSV opens up after engine warm up, not sure exactly.

Attached is the pic of the hose on the other side of the manifold.

 

[Splangy]

At work, but the nipple is on the driver side of the intake manifold near the rear/firewall. The hose literally goes from the nip to EGR in about 5-6 inches of hose....

Does anyone know if it's suppose to have VAC at all times or only at certain RPMS?

P.S. Where does it connect on other side? I might bypass it temporarily ...

That port isn't supposed to have any vacuum. That port goes to the VSV, not the vacuum source. The vacuum source is from the throttle body, through the modulator.

The VSV closes to allow the vacuum source from the modulator to open the EGR valve.

The FSM is your friend.

 

[thestunts]

Thank you for replies.

 

[danimal24]

Been following these threads.
Try this. My VSV has good resistance, closes when I give 12 volts, has 12 volts of potential when key on, have 12 volts at ECM.

When the truck is warm and I rev engine, the valve stays open! It should close...any thoughts on ECU inputs that signal to close it?

Thanks mud!

 

[thestunts]

So I found this YouTube EGR testing.

• 
  
  Following the instructions got the following...
  
• Applying Vacuum to passenger side of EGR, causes stumble (as it should)
• Applying Vacuum & pinching VSV tube, dies (as it should)
• Applying Vacuum & pinching tube on driver side of EGR, nothing. (should have stopped)

Also, I found a thread on testing voltage to the VSV plug. Applying voltage, zero air passes. Without voltage, air passes. But barely, definitely not freely.

So I'm not sure if its a partially functioning VSV and/or gunked up passages. I'm gonna attempt to clean the passages without removing the TB or intake manifold.

Anyone have any input on the above information?

Also, I tried using the pipe cleaner things with no luck ... anything else I can shove through there? or do I have to remove the TB and what not?