Need help with P2646

[Fat_Hatch]

Just bought this 04 Civic SI two weeks ago. Drove on the highway for 2 hours after picking it up and the check engine light comes on. Had a few days where I was really busy and didn't have time to check it out so I just drove with it on, didn't have much of a difference in driving other than a slight hesitation at around 2200 rpm. Later the check engine light goes off but the hesitation is still there. Engine light stayed off for a few days until I changed the oil. I looked at the manual and used 5w-20 Castrol Edge Extended performance. Well not even a day later light comes back on and I just got it pulled at an auto parts store. It's P2646 & P0172. I started reading online for the past day or two and saw that 5w-20 is probably bad for the oil-pressure-sending-vtc-unit-thing. Which could potentially cause P2646. I have yet to check the level but I mean its only been 3 days since oil change.

So I needed some clarification from the information I read online. I need to know other than the oil, if item 4 or item 7 in the picture below would cause P2646 code, or could it be both that can cause that code, if those units go bad. How would I go about trouble shooting them. Should I stop driving the vehicle until it's resolved? I seen a post on here about this code and the engine imploding, do I need to worry about that?

Thanks for all your help!

S5S4E1001.jpg

[sp00n sp0rts]

you are correct on for number 4 but number 7 is wrong its jus oil sludge or dirt that is stuck in number 4 and also number 10 you jus have to clean it with break cleaner and the inside of 10 and to be on the safe side jus switch out number 4 with a new one. its called spool valve on the website hondaautomotiveparts but when it comes to our manual its the vtec solenoid valve.. mine went on last week then did the research coz at first i thought if it was bad but its not that bad. something you dont have to worry about but its a simple fix the good thing is i did find a video on youtube https://www.youtube.com/watch?v=4SBY0O8a8dw good luck bro hope this helps..

[Fat_Hatch]

you are correct on for number 4 but number 7 is wrong its jus oil sludge or dirt that is stuck in number 4 and also number 10 you jus have to clean it with break cleaner and the inside of 10 and to be on the safe side jus switch out number 4 with a new one. its called spool valve on the website hondaautomotiveparts but when it comes to our manual its the vtec solenoid valve.. mine went on last week then did the research coz at first i thought if it was bad but its not that bad. something you dont have to worry about but its a simple fix the good thing is i did find a video on youtube https://www.youtube.com/watch?v=4SBY0O8a8dw good luck bro hope this helps..

Thanks Spoon Sports for the video. That does make it look pretty easy to clean. I think the next steps I'm going to do is clean out the screens on part 4 and part 10 then also change the oil to 5w-30. The hesitation at 2200 is rather annoying because I can't drive normally or I guess I can't drive smoothly. I hope these steps helps the hesitation.

[sp00n sp0rts]

it is annoying to say the least but when its all done its back to normal you could clean out number 4 but if it stays the same jus change it out.. nowadays people are running 5-30 for their ep3 but for me i still stay at 5-20. well good luck let me know what will be the outcome..

[beechstreet]

For P0172 check these:
For Fuel control sensor is out of calibration (ECT, IAT or MAP sensor)
Leaking/contaminated fuel injector(s)
EVAP vapor recovery system has failed (pulling vacuum)
Fuel pressure regulator has failed (high fuel pressure, or it may be leaking)
Partial engine misfire condition present in one or more cylinders
Base engine fault (e.g., cam timing incorrect, oil level too high)
AFS has failed (it may be contaminated with fuel, silicone and / or water)

[Fat_Hatch]

So I had a few hours to look into the car this past week. I cleaned the screen in the spool valve. That was a pain to put back in, pretty much blind trying to line up the bolts. Car still has check engine light, but it goes off randomly and comes back on randomly the few days I did drive the car. So I thought I may try replacing the PCV valve and the spark plugs because they're unknown to me if they've been replaced or not. So I got the PCV valve in easy. When I took my coil packs out, cylinder 1 looked kind of bad. Then I took out the one in cylinder 3 and that one was really bad. I mean it was crumbling at the end and cracking. Cylinders 2 & 4 looked ok. I don't have any misfires but do you think, a bad coil pack can cause a slight hesitation at 2,200 RPM? Also do you think it can cause the 'system too rich' code P0172?

Thanks!

[Fat_Hatch]

Just an update. Replaced all coils, all spark plugs. Replaced spool valve. Car runs just the slightest smoother but still has the hesitation right at 2200, like a flat spot or a dead spot. Sometimes feels like the car is stutters for a split second. More noticeable in 1-2 gear. Anyways, the check engine light was off the whole time and just came back on again, about to go get it checked again to see if it is still the P2646 code. Still hunting this weird hesitation down.

How can I check the MAP/IAT/ECT sensor to see if they are still working normally? Also I guess i don't know if this matters or not but the car came with an AEM cold air intake.

Is there a method of checking if the EVAP system is pulling vacuum without any special equipment/tools? Spraying carb cleaner around the tubes?

Also what is "AFS" according to Beechstreet's post.

[Fat_Hatch]

Just an update. Replaced all coils, all spark plugs. Replaced spool valve. Car runs just the slightest smoother but still has the hesitation right at 2200, like a flat spot or a dead spot. Sometimes feels like the car is stutters for a split second. More noticeable in 1-2 gear. Anyways, the check engine light was off the whole time and just came back on again, about to go get it checked again to see if it is still the P2646 code. Still hunting this weird hesitation down.

How can I check the MAP/IAT/ECT sensor to see if they are still working normally? Also I guess i don't know if this matters or not but the car came with an AEM cold air intake.

Is there a method of checking if the EVAP system is pulling vacuum without any special equipment/tools? Spraying carb cleaner around the tubes?

Also what is "AFS" according to Beechstreet's post.

Secondly, I've noticed that while I'm driving sometimes when I'm coming to a stop and a pull the car out of gear to neutral, the rpms would drop to below normal idle rpms, almost to 0 and then bounce back up to 800-900 rpms.

***update 6/7/16***
I went to the auto parts store and they ran the code and P2646 is no longer there, the only one is the the p0172 which he said was bank 1 o2 sensor. Well I guess I'm buying a new o2 sensor.

[usedep3]

Secondly, I've noticed that while I'm driving sometimes when I'm coming to a stop and a pull the car out of gear to neutral, the rpms would drop to below normal idle rpms, almost to 0 and then bounce back up to 800-900 rpms.

Sounds like IACV needs to be cleaned

[Fat_Hatch]

Sounds like IACV needs to be cleaned

Hey usedep3,

Thanks for the tip for cleaning the iacv to help with the idle issue. I'll make sure to do that next. Do you have any knowledge on how the car would react to changing the intake from the oem air box to the cold air intake? Can the car compensate for that change? I've read some people with the newer civics (k20z's) that sometimes needed to get a flashed ecu or whatever to get the most out of it and sometimes just to clear the P0172. I'm debating on either buying a stock air box if that may help with this issue.