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Discussion Starter · #1 · (Edited)
My CEL came on this week w/ a P0401 code. I checked out the EGR valve, VSV solenoid and modulator. When I apply vacuum to the the EGR valve, there is no change in engine rpm. The valve does hold vacuum. The VSV and modulator checked out OK.

I removed the valve today and gave it a good cleaning. I applied low pres compressed air to the exhaust side. No flow w/o vac applied and flow w/ vac applied.

Reinstalled valve and still no change in rpm when vacuum is applied. Seems like either the tube from the exhaust is plugged or the passage from the EGR valve to the intake is plugged. I'm thinking the latter.

I haven't found any procedure for cleaning the passage in the intake manifold.

Has anyone has a similar experience? How does one go about cleaning that passage?

fwiw: Before the CEL came on the engine has had (and still does) what I thought was a ignition miss under load. I've checked out the ignition system and haven't found anything.
 

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Discussion Starter · #2 ·
I pulled the EGR valve again today and took a mirror to look at the passage between the EGR mounting flange and the intake. It was totally plugged w/ carbon. I removed the throttle body and be able to see the other side and was able to clean out the ~0.25" dianmeter passage between the EGR and intake.

While it was out, I also gave the throttle body a long overdue cleaning.

After reassembly, the engine nearly dies when I apply vacuum to the EGR (as it should).

Can't say it was fun, but it's good to get to the root cause of the problem.
 

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rock crawler
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I had a similar problem with my 84 a few years back, the path in the manifold was completely blocked with carbon. I used a drill bit in my hand to drill through it and with a vacuum sucking it out. Kind of a PITA but it worked.
 
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