Hi; this is a very very mysterious problem. I will stgart by saying ive had 3 shops tell me theres no exhaust leaks. One being a specialty exhaust shop.

Have had a code; p0401 for 3 years now. (exhaust gas recirculation problem) Tried replacing egr valve - no dice.

I replaced the exhaust manifold and gaskets before and after it. I tore the thing apart and did the head gasket; all oil seal; while i was in there i did the intake manifold cleaning that people on youtube say will fix p0401. i will never do that again. removing it from the back of the engine was the worst job ive ever had to do. worse than changing an alternator on the side of the road mid january freezing temps.

still have the code.

i have exhaust fumes pumping carbon monoxide in my cab. i have measured with a kidde CO meter; and a 100$ klein tools CO meter. i get ~35-45 ppm with vents on reguler. then; when i hit recirculate; the fumes stop; but only when car is idling. soon as you hit the gas; somehow the recirulate still brings CO in!!!!!! i drove like this without knowing it for almost 12 months and i almost died one day. I have been healing since from stroke like symptoms from sleeping in the cab overnight with fumes .

There is an oil leak. i fixed from valve cover and rear cam seal; \

exhaust shop told me to fix oil leaks because they can burn off the engine

but why would my recirculate bring 35ppm CO into my cab going 60 mph down the road????

i still have a leaking oil pan gasket; changing the oil pan itself now because TWO oil pan gasket jobs, one i did, one a shop did; failed!!

shops told me rear main seal is okay! i have rear main sealer in the engine to make sure!

All the other seals have been done; and no mechanics think its leaking anywhere except the pan gasket.

Im afraid im going to fix the pan gasket; get that leak to stop; and sitll have fumes coming in the car becasue of 2 things
1: p0401 exhaust problem which no shop has any explanation for me
2: going down highway at 60 with recirculate still bringing fumes in!

How hard is a recirculate door to replace? i cant find any guides for it anywhere! I dont think thats the propblem thouigh; becasue i can hear the difference when i hit the recirc button.

274k miles. but i just successfully did the headgaskt; timing water pump a/c, alternator, front undercarriage , newer speakers, i really love this car. i ahve 1300 to do rear struts new wheel assemblies rims and tires CPR up front because current rims and wheel assemblies are warped (yes the wheel hub assemblies caus my rottors to warp over and over because the studs are all crooked and make my rims ride weird due to people using the studs the lever their breaker bars / pry bars when working under there before)

but im not gonna do any of this if i cant get the fumes to quit coming in the cab.

tested my 03 civic EX for same problem.. i dont get same issue. only a tiny bit of CO with vents on reguler without recirc... and only because of a opil leak from rear cam seal and valve cover gasket which i just redid both with "right stuff" from permatex since the shop who did both gaskets had them leaking again within half a year! i think these old hondas just need help with gasket maker on new gaskets in these areas, cus both my hondas do it. either that or these cheap part manufacturers are making gaskets out of spec. but i always buy the "better" quality parts so thats over my head.

Anyways; if anyone can help me, please let me know what your experiences have been / expertise tells you . Thanks

Ryan