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Pete, Auto Service Technician
Category: Toyota
Satisfied Customers: 24145
Experience:  Over 17 years diagnosing and repairing automobiles various makes and models with some training and certifications.
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4runner: What if no air goes through but there is a burn spot

Customer Question

What if no air goes through but there is a burn spot on the felt packing?
Submitted: 6 months ago.
Category: Toyota
Customer: replied 6 months ago.
Original question was vague. I was referring to testing the EGR MODULATOR on a 92 Toyota 4Runner 4x4. Vehicle failed smog for high NOX. I read that it can be checked 2 ways. One is to blow air into the bottom vacuum inlet and if air passes through, it's bad.
Customer: replied 6 months ago.
The other is to check for burn spots on the filters inside the egr modulator. Turns out it has a burn spot but the air won't pass through when I blow into it. All of this is part of a bigger concern... Why aren't I getting vacuum at the EGR valve? When I rev the engine, the plunger on the EGR valve doesn't move. I removed the VACUUM line coming off the top of the EGR valve and revved the engine again and should feel suction coming from that line but I didn't. Therefore, my EGR valve isn't opening when my engine is being revved and it's causing me to fail smog. I checked the EGR valve to ensure that it holds vacuum and it does. I even removed it and cleaned any deposits that may have accumulated. Still no movement of piston when I rev the engine.
Expert:  Pete replied 6 months ago.
My name is ***** ***** I am a professional here at Just Answer. I noticed that your question had not received a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here. It sounds like the EGR modulator itself needs replaced and is the cause here.I have seen this fail before internally like this needing replaced.Make sure all vacuum hoses and connections are clean and tight and if found o.k. I suspect the modulator needs replaced to correct this issue here. If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.Thanks Pete

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