Question
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Followup To
Question -
Hi HT
I have a 2001 sonata 4cyl. Check engine lite comes on and code reads EGR. After engine warms up I pulled vacuum line from EGR brought rpm's up. I should have felt atleast some vacuum, but i don.t. Is there an elec. selinoid that controls this? Vac line seems good.
TIA Frank
Answer -
Hi, Frank. You say pulling the vacuum hose off the EGR increased the engine rpm? If that's the case, I don't understand why there's no vacuum in the line. That'd pretty much imply the valve was open and it closed when you pulled the hose off.
Here's how the system works:
There's vacuum in the green hose coming off the throttle body. This hose tees to the EGR valve and the egr solenoid. Under normal conditions, the EGR solenoid valve is off (open) allowing the vacuum to vent back to the throttle body through the yellow hose, and preventing the vacuum from reaching the EGR valve. When driving, the computer operates the EGR valve by turning on (closing) the egr solenoid valve, removing the vent pathway and resulting in the vacuum reaching the EGR valve.
If your EGR valve is open while the car is idling, you have one of two problems:
The vent pathway is blocked (usually stuck closed EGR solenoid) or the EGR valve itself is stuck open.
If the EGR valve is closed at idle, you can simulate activating the solenoid by pinching shut the yellow hose at the throttle body. If the EGR valve opens and the engine runs very poorly, then you already know that the vacuum lines, the EGR valve, and the EGR passages are operating properly.
In addition to the above components, there's also a vacuum bleed-off valve that meters the vacuum to the EGR valve. I've worked on a couple cars where these have gone bad, but have not found any way to concretely test whether they're working properly other than trial and error. In once case, it did appear that the EGR valve opened much more quickly with the new bleed-off valve.
Sorry HT
Bad wording on my part. I pulled vac line, then I raised RPM's,to see if EGR was getting vacuum. It did not. Hence my question about a soleniod switch. From what you are saying there is one. Where might that be located and how to check function?
Again Thanks,Frank
AnswerYou won't be able to get vacuum to the EGR valve when the car isn't moving, so not having vacuum when you rev the engine doesn't really mean anything.
First, start with the test I mentioned previously to determine whether the EGR valve and all the plumbing operate normally.
If so, then check the solenoid valve. It'll be located on the back of the manifold on the right side of the car. It has one pink and one light blue wire in the connector and should have a green vacuum hose going to it. Turn the key on and check the pink wire for power. If okay, start the vehicle and ground the light blue wire-- this will probably set a trouble code for the EGR solenoid circuit. The EGR valve should open. If it doesn't, but did in the test I mentioned in the initial response, the problem is with the EGR solenoid.
If the EGR operates when you ground the light blue wire, then I think there are only two possibilities:
1. The solenoid is intermittently sticking (but working okay now). If this problem is always present, then I wouldn't expect this to be the case. Shoot for this if you know you have an intermittent problem.
2. The vacuum bleed-off valve relieves vacuum too quickly. This is typically not an intermittent issue.
These parts are often hard to find in the parts catalog, especially the bleed-off valve, so I'll give you the part numbers for each.
Bleed-off valve (aka vacuum switch valve): 28378-38050
EGR Solenoid valve: 39460-38750
The bleed-off valve is about an inch and a half in diameter and about a half inch thick, with two nipples coming off one side. It'll be mounted to the back of the intake manifold also.
