DIY Intake Manifold & EGR Valve Gasket CEL P0420

gsrteg · Feb 16, 2013

Long story short I changed my Intake Manifold & EGR Valve gaskets due to a code P0420. Checked all Primary O2 sensor, spark plugs, fuel injectors, timing, and exhaust all was good. I narrowed it down to the Intake Manifold, IACV and EGR.

Tools:
-3/8 rachet, air rachet if you have one
-3/8 extensions
-3/8 universal joint
-10mm,12mm,14mm sockets
-phillips screw driver, flat head
-needle nose pliers/adj. pliers
-razor blade
-shop paper towels
-tooth brush, q-tips, wire
-throttle body cleaner/brake cleaner
-copper gasket spray

Parts (OEM HONDA PARTS ONLY) prices may range from your area, cheaper online:
-18715-PB2-000 (GASKET, EGR VALVE) $4.67
-17115-PAA-A01 (GASKET, IN. MANIFOLD) $4.05

First off, take the intake box and tube/pipe off. Then remove all hoses, electrical plugs, clamps and components off the intake manifold.

Then begin removing the 5 bolts for the upper portion of the Intake Manifold and 2 bolts holding the EGR Valve.

Once off, begin cleaning all the intake ports, throttle body, IACV valve and EGR ports. Use the razor blade to scrap off old gaskets and build up around the mating surface. Use the tooth brush and q-tips with the brake cleaner/throttle cleaner to clean all of the gunk inside the intake mani. This part can take some time. Be carefull not drop anything down the ports, if you do use a needle nose plier to pick it out. Use the shop paper towels to wipe off excess gunk build up.

Use the wire to clean the EGR ports and use an air blower to blow the port out. Make sure you clean the EGR Valve as well, and the IACV Valve while everything is off.

Lastly, use the copper gasket spray to coat only the Intake Manifold gasket. Give it 3 flash coats on both sides before putting it on. By using the copper spray, I noticed it allowed a better seal and reduces the chance of air leaks/vacuum leaks. Once dried, install it. And install the EGR valve gasket. Install everything in reverse. You should be good afterwards. After doing this, I noticed the CEL went away completely.

BlkCurrantKord · Feb 17, 2013

Wire brush on the end of a drill works too

001Stunna · Feb 17, 2013

Great job on all that you did but outta curiosity...how did you go from p0420(cat.converter under threshold) to the intake manifold, iacv, egr???

gsrteg · Feb 17, 2013

001Stunna said:
Great job on all that you did but outta curiosity...how did you go from p0420(cat.converter under threshold) to the intake manifold, iacv, egr???

I dunno. However, I noticed during the time, the p0420 code kept kicking on/off. I took it to autozone, and guy used his OBD2 scanner and told me I needed to buy a new O2 sensor. I was kinda skeptical. I used a buddys OBD2 scanner to test the voltage readings for both O2 sensors. And they both seemed to be close to range readings. I tested the catalytic converter by using a temperature gauge gun and my catalytic converter seemed to be operating like it should. Thanks to EricTheCar (http://www.youtube.com/watch?v=9VZ5K8n5jj0).

So since I confirmed all my O2 sensors were FAIRLY good and Catalytic Converter was good, i did more research on the net, causes for P0420.

OK! There are a couple things that could cause p0420 catalyst efficiency code. The most common thing is the catalytic converter, and most end up changing this.. Other things is the rear O2 (oxygen) sensor damaged, exhaust leaks, damaged exhaust pipes, short in O2 sensor wiring/connectors, plugged catalytic converter, etc. So i started diagnosing all these other components and more research.

Back to the EGR Valve and EGR passages.. What is the purpose of an EGR VALVE? Well read on this: http://www.ehow.com/about_5047751_functions-egr-valve.html. If the ports are clogged, then the engine cannot cycle exhaust gases back through the engine to "dilute" the fuel/air charge causing a slightly "rich" condition. EGR systems are to reduce emissions and increase fuel economy as well (most dont understand this), especially at cruising speeds (>45mph). SO, if the fumes are too rich, the downstream o2's sample the fumes and the voltage reading indicates a "low efficiency" after the catalyst, you get a Check Engine Light.

SO, i began doing an experiment, by taking the EGR valve off, and notice a SH!T Load of carbon build up and gunk that was clogging the EGR Valve and ports in the intake manifold. The IACV probably had nothing to do with the code, but i just decided on my own to take it apart and clean it. The intake mani gasket probably didnt have anything to do with the code as well, but i was just in the moment and wanted to clean/change it. And this was my end result.

AccordUser · Feb 17, 2013

gsrteg said:
I dunno. However, I noticed during the time, the p0420 code kept kicking on/off. I took it to autozone, and guy used his OBD2 scanner and told me I needed to buy a new O2 sensor. I was kinda skeptical. I used a buddys OBD2 scanner to test the voltage readings for both O2 sensors. And they both seemed to be close to range readings. I tested the catalytic converter by using a temperature gauge gun and my catalytic converter seemed to be operating like it should. Thanks to EricTheCar (http://www.youtube.com/watch?v=9VZ5K8n5jj0).

So since I confirmed all my O2 sensors were FAIRLY good and Catalytic Converter was good, i did more research on the net, causes for P0420.

OK! There are a couple things that could cause p0420 catalyst efficiency code. The most common thing is the catalytic converter, and most end up changing this.. Other things is the rear O2 (oxygen) sensor damaged, exhaust leaks, damaged exhaust pipes, short in O2 sensor wiring/connectors, plugged catalytic converter, etc. So i started diagnosing all these other components and more research.

Back to the EGR Valve and EGR passages.. What is the purpose of an EGR VALVE? Well read on this: http://www.ehow.com/about_5047751_functions-egr-valve.html. If the ports are clogged, then the engine cannot cycle exhaust gases back through the engine to "dilute" the fuel/air charge causing a slightly "rich" condition. EGR systems are to reduce emissions and increase fuel economy as well (most dont understand this), especially at cruising speeds (>45mph). SO, if the fumes are too rich, the downstream o2's sample the fumes and the voltage reading indicates a "low efficiency" after the catalyst, you get a Check Engine Light.

SO, i began doing an experiment, by taking the EGR valve off, and notice a SH!T Load of carbon build up and gunk that was clogging the EGR Valve and ports in the intake manifold. The IACV probably had nothing to do with the code, but i just decided on my own to take it apart and clean it. The intake mani gasket probably didnt have anything to do with the code as well, but i was just in the moment and wanted to clean/change it. And this was my end result.

nice job, im at the same position you are, prior to all the work, lol. i did the intake mani and egr which kept the light off for sometime then came back, ill be doing my iacv when it gets warm out.

gsrteg · Feb 18, 2013

AccordUser said:
nice job, im at the same position you are, prior to all the work, lol. i did the intake mani and egr which kept the light off for sometime then came back, ill be doing my iacv when it gets warm out.

Good luck, keep us updated. I saw your thread. Yours is a V6? The problem with my car is, the code would flicker on every now and then. Then at one point the code was just on for a week. I got tired seeing it on my dash. So did my own research. I didn't feel like just wasting a bunch of money on various parts.

AccordDriver95 · Apr 24, 2013

Hey, as for taking off the lower half of the IM for further cleaning and replacing the gasket. What would you need to do to prep for it? Drain coolant or oil or both? Also would i need to do anything special or out of the way for removing the fuel injectors? Sorry if these are idiotic questions.

noelaorozco · Apr 24, 2013

good thread, i have the same problem, my check engine lights has been on forever and i recently tried to half *** clean the egr valve which was pretty full of gunk and i restarted the check engine light but it came back on. gonna need to probably take off the valve and intake manifold this time

sr.sedan · Apr 24, 2013

Good info man :thumbup:

gsrteg · Apr 29, 2013

sr.sedan said:
Good info man

Thanks!

DIY Intake Manifold & EGR Valve Gasket CEL P0420

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