Hey All,
I'm tracking down a P401 insufficient EGR issue. I've followed the FSM to check for vacuum at the EGR valve during cold/warmed up at 2500 rpm as well as moving the vacuum line from the modulator to the vacuum circuit. I did not see vacuum at the EGR valve in any of those conditions. The next test in the FSM (connecting the EGR valve directly to vacuum) resulted in the correct stalling of the engine since the EGR valve opened.
From there I tested the EGR modulator per the FSM (blowing air thru it and verifying it comes out the vent at the proper times). That passed as well. I was a bit surprised at this since I was not able to get the EGR valve to open when I connected the modulator port to directly vacuum in the FSM test. Does that indicated a failed modulator?
So based on that it would seem the EGR circuit on the exhaust gas side is working. The line from the VCS has been pinched off to isolate it as not the problem.
During this testing I noticed the two lines that go from the intake/throttle body to the EGR modulator valve both have no vacuum. Is that correct? I would seem one of those needs to supply the vacuum to open the EGR valve. However from the schematic in the FSM it seems to show both those lines are ahead of the throttle valve. To try to understand it better, I probed a few lines with my vacuum gauge and saw there are a couple lines that don't pull vacuum. Can someone clarify what ports should have vacuum present at them? I suspect I have a plugged port somewhere that is causing my issue.
I'm tracking down a P401 insufficient EGR issue. I've followed the FSM to check for vacuum at the EGR valve during cold/warmed up at 2500 rpm as well as moving the vacuum line from the modulator to the vacuum circuit. I did not see vacuum at the EGR valve in any of those conditions. The next test in the FSM (connecting the EGR valve directly to vacuum) resulted in the correct stalling of the engine since the EGR valve opened.
From there I tested the EGR modulator per the FSM (blowing air thru it and verifying it comes out the vent at the proper times). That passed as well. I was a bit surprised at this since I was not able to get the EGR valve to open when I connected the modulator port to directly vacuum in the FSM test. Does that indicated a failed modulator?
So based on that it would seem the EGR circuit on the exhaust gas side is working. The line from the VCS has been pinched off to isolate it as not the problem.
During this testing I noticed the two lines that go from the intake/throttle body to the EGR modulator valve both have no vacuum. Is that correct? I would seem one of those needs to supply the vacuum to open the EGR valve. However from the schematic in the FSM it seems to show both those lines are ahead of the throttle valve. To try to understand it better, I probed a few lines with my vacuum gauge and saw there are a couple lines that don't pull vacuum. Can someone clarify what ports should have vacuum present at them? I suspect I have a plugged port somewhere that is causing my issue.