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Hello all, I have searched & searched and am dumbfounded.

History: 2003 Civic EX (Vtec) manual. new to me with 159,000 miles. Bought it in SC drove fine, no codes. All seemed well. About the time I got to Atl GA the car overheated on an epic level. Pulled over immediately addressed the situation. Long story short, upon investigation and mechanic inspection of cooling system, previous owner patch fixed with leak stop. I don't go into motors, so it went to my trusted mechanic. Confirmed very very bad blown head gasket, I came and inspected during repairs. I noticed the horrid carbon in the intake tract while car was apart. I asked him to please clean everything out, as the car was apart. I got pictures of a cleaned intake tract, and I even reviewed a few pictures I took when I visited a 2nd time that confirmed the tract in the intake was clean. Repair complete.

Present issues: I take the car home. It begins coding for P0401 EGR insufficient flow within 20 miles of driving. Car previously never had a code during the long drive from SC to GA, it passed GA emissions fine. I assumed maybe carbon flakes after cleaning intake could have blocked the egr itself, so I removed EGR & cleaned it. Passages below EGR look clear. I Cleared codes, drove it and the code returned. I reached out to the mechanic. He says try to swap to a new EGR. I go pick up a new one with new gasket & swap it out. I clear codes and the dang P0401 comes back. It always shows up pretty fast too. Within 20 miles after codes are cleared when driving the Honda drive cycle.

So what else can it be causing the issue?
1. The only thing I can think is the wrong intake gasket was installed (no EGR passages). However the parts were ordered from HONDA by the shop using the VIN. Does Honda include multiple gasket versions in their head gasket kit? Could the wrong one have been installed?
2. Or is it possible that the EGR passage in the head itself is clogged? I know its common for the intake portion to clog, but does the head port commonly get plugged up. It is the only passage way that I can't inspect or have pictures of during the install to see its has been cleaned.

I picked up some BG44K Platinum and was tempted to run it through thinking it just might be a bit of residual carbon in the intake that a light chemical cleaning might resolve. This is all I can think of to try outside of breaking the whole motor apart again. Tonight I am going to try unplugging the sensor and running power to EGR terminal 4, then idle & then connect negative to terminal 6 and see what the car does.

Any other thoughts, ideas? Beyond the above I am out of ideas. Thank you!

 
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I would pull the manifold off and check that the right intake gasket is installed

 
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take back to the mechanic...

 
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The EGR diagnostic test I ran last night did verify there is an egr tract block, as the car did not stall or run rough when the EGR was energized manually.

Just spoke with the mechanic and reported the results. He said he could take a look back at it the first week in September. He is a solo guy running his shop, so I can't be mad at him for the delay. He said in the interim I could pull the thermostat/ EGR housing and check the port that runs through the head prior to the intake ports. I mentioned the gasket possibility and he said its possible, but check the head port first. He would do it but he is slammed with cars. He said if that head port cleaning/inspection does not sort it out he will go back over everything.

 
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The more likely cause imo.

Look around the edges of the valve cover, can you see blue colored gasket anywhere?

 
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Sorry for the delay. I have been fighting a nasty set of migraines. Have not messed with the car yet.
Valve cover gasket appears to be black. I had them use OEM for everything. All part were supposed to be verified via the vin number. What does the blue gasket indicate?

 
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FelPro (trademark?) blue gaskets.
Just checking, I was thinking their sets included both versions of the intake gaskets.

I have Charlie Brown's luck.
2 to choose from = 50/50 chance of being right, but Ill pick the wrong one 90% of the time.



There are several posts in this forum about wrong intake gaskets and p0401.

It's been a hot minute since I did this job, I dont have a genuine Honda set to inspect. From fuzzy memory I dont think hondas sets included both versions,

But I can tell you if the wrong hg set was received by the mechanic , the few differences between sets may not be obvious nor a big obstacle, and it could go completely unnoticed during assembly.

And as you witnessed the problem is not readily apparent, it took what 20 miles of driving before you saw the first clue in the form of the yellow check money light.

 
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Thank you for the insight... I do know a blue one came off the car.

Yep... car runs fine until the CEL light sets.

When the Mechanic and I discussed.... He paused and thought for a second and said, "I guess its possible the wrong gasket got installed. just check that thermostat/egr housing port first though."

Well for the heck of it, I bought a borescope to go with the job. Figured I would shove the sucker in the port while I had the EGR/Thermo housing off. Maybe with some luck I could get a clear enough shot to tell if the EGR port main hole is present in the gasket or no. Would at least tell me something before the mechanic and I have to crack this beast again. Now to actually get to the job. UGH... its been one of those weeks, hoping this week is of a gentler sort.