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Following a replacement of the knock sensor on my 2003

Pilot(rodents at the wires) I...
Following a replacement of the knock sensor on my 2003 Pilot(rodents at the wires) I put it all back together and the car behaves normally, but when idling in park and neutral, the engine rev-cycles... vroom... vroom... all by itself. My local mechanic suggested that the knock sensor, not being a factory part, is to blame. Is there a way for me to disconnect that sensor to see if the revving stops, without tearing it all down again? I had a hard time accessing that connector, and was wondering if I could somehow disconnect the other end. Thanks in advance!
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Answered in 9 minutes by:
2/5/2020
Mechanic for Honda: Adam H, Auto Mechanic replied 2 years ago
Adam H
Adam H, Auto Mechanic
Category: Honda
Satisfied Customers: 23
Experience: Shop Foreman
Verified
Hello my name is*****’m a Honda master technician
With over 15 years experience. Do you have a check engine light on the instrument cluster?
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Customer reply replied 2 years ago
No, the light isn't on. I have a reader and can do a full diagnostic, but haven't done so yet.
Customer reply replied 2 years ago
I texted you back online but perhaps you didn't get my answer. The check engine light is off. I have a reader and can do a full diagnostic but I haven't done that yet.
Customer reply replied 2 years ago
I'm getting crickets, Adam. Can you answer my question, please?
Mechanic for Honda: Adam H, Auto Mechanic replied 2 years ago
Sorry this is the first alert I got. If you have a scan tool that will read fuel trim look at st fuel trim. Most likely you have either a bad idle air control valve or a vacuum leak. The short term fuel trim should be very close to 1.0. Check this and let me know
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Customer reply replied 2 years ago
Thanks I'll try that tonight
Mechanic for Honda: Adam H, Auto Mechanic replied 2 years ago
If your value is above 1.00 and stays that way most likely you have a vacuum leak somewhere. You can use propane or brake clean to spray around the intake plenum and see if the idle changes.
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Customer reply replied 2 years ago
Hello again Adam,
I started the car and this time the check engine light came on and ran full scan. It has a p0505 "Idle control system" confirmed code and the BlueDriver app suggests the fixes you mentioned: Base engine vacuum leak, IAC valve failure, PCM failure Throttle body/plate is dirty. I cleaned it really well before re-installation so that's not it. I sprayed brake cleaner all around the plenum and throttle body/air cleaner and nothing changed in the revving behavior. I have some screenshots of the short term fuel trim and under load, (in drive with e-brake on) it oscillates +/- around 0% and the engine is sound smooth. In Park the revving oscillates the STFT from 0% to -3.1%. I think the reporting of the value is slower than the rev frequency (about two revs per second). I can send you a screenshot of the PID sensors. See attached.
Customer reply replied 2 years ago
Thanks in advance. I know it's kind of a data dump on you. I'll be signing off soon and travelling all day tomorrow. (away from the car) I'll check your response but can't act on it until Saturday afternoon.
Mechanic for Honda: Adam H, Auto Mechanic replied 2 years ago
a p0505 trouble code is most likely a faulty iac valve. This is located on the bottom of the throttle body. When you replace it I would also clean the throttle plate with gum cutter cleaner. That valve will cause rpm fluctuation. You can take a beg screwdriver and tap on it while it’s running and getting warm. This may change the idle if so you know for sure it’s a faulty valve.
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Customer reply replied 2 years ago
Hello again Adam, I'm back at the repair now. I had a couple of hours this morning so I pulled off the air box, blew the air filter clean, pulled off the throttle body, and removed the IAC sensor to see if there was any obvious problem. Other than some minor carbon in two (of three) of the chambers, it looked healthy at least from the outside. I cleaned the carbon I could reach in that part, cleaned out the throat of the throttle body which was honestly pretty clean as well, then put it all back together and did the whole "learning" process of 5 minutes at 3000rpm, two fan cycles followed by 5 minutes of AC.(as suggested by a youtuber) When the RPM dropped down from 3000 rev cycling was same as prior. While it was running, I unplugged the IAC sensor and there was no effect.(still revving 2-3 Hz) Does this prove its malfunction? I can buy a new IAC but was doubting its problem since this only started happening after I changed the knock sensor. I COULD be a coincidence, that it started malfunctioning as a result of of the repair, just want to avoid buying a sensor if unnecessary. The pictures I'm attaching were actually taken before I got the throttle plate clean. It's down the bare metal now. Thanks for your time.
IMG_6915.JPGIMG_6915.JPGIMG_6916.JPGIMG_6916.JPGIMG_6917.JPGIMG_6917.JPGIMG_6919.JPGIMG_6919.JPGIMG_6922.JPGIMG_6922.JPG
Customer reply replied 2 years ago
Oh, I also tried tapping on the IAC at different times, but that had no effect on the rev cycling.I would have pulled the solenoid off the sensor body to investigate more, but it is attached with a 5-point starred screw, which to me is an indication not to f with it.
Customer reply replied 2 years ago
One other quick question... when looking for parts, I can pay $42-80. What is the risk with the cheap one?
https://www.partsgeek.com/catalog/2003/honda/pilot/fuel_injection/idle_control_valve.html?rp=idle_air_control_valve
Thanks again, and enjoy the rest of the weekend!
Mechanic for Honda: Adam H, Auto Mechanic replied 2 years ago
I have used aftermarket with success in the valve. 99 percent of the time p0505 is directly related to iac valve. If the pilot sat for any length of time while you were replacing the knock sensors it’s common to stick and go bad. Other than a vacuum leak which you have already checked for and not found anything, my next step would be to replace that valve. Make sure after you replace the valve you bleed to cooling system to ensure no air is trapped in the valve. Also after replacing the valve as long as it repairs you problem you will need to unhook the battery for about 5 mins to reset the pcm and after starting turn off all electrical loads and let it idle for atleast 10 minutes. This is how the pcm learns the correct idle speed. My honest opinion is the solenoid control for the valve is faulty causing this problem.
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Customer reply replied 2 years ago
Thanks for your detailed description, Adam. I'm not sure how to bleed the cooling system. Can you send me a video link for that, or simple instructions? Thank you!
Mechanic for Honda: Adam H, Auto Mechanic replied 2 years ago
If you have a funnel that will fit into the filler neck on the radiator and hold tight fill it with coolant and let the car run until the thermostat opens, if not just be sure to fill the cooling system slowly and if you have a ***** *****ft the front of the pilot up. This will make all the air push to the highest point and let the air escape.
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Customer reply replied 2 years ago
Got it. I have a steep driveway, so the bleeding will be easy. I assume that as long as the car is on a steep angle when the thermostat opens the bleeding will be successful. Thanks again, Adam!
Mechanic for Honda: Adam H, Auto Mechanic replied 2 years ago
that should work. It not super hard to get the air out of the valve just want to be sure you don’t get an air pocket trapped in the heater core and have no heat. Let me know when you replace the valve, I want to be sure that everything is good. Thanks for your patience with me I work two other jobs and stay busy all the time.
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Customer reply replied 2 years ago
Yeaaah baby! A new IAC valve is exactly what it needed. I did the "relearning" process and it idles and runs like a champ... AC and heater both work. I really thought the error was with the assembly I did, but it looks coincidental. I never unplugged the battery the first few times I took it apart. I thought it was an unnecessary precaution. Could the solenoid have failed by me hot-dis/connecting it? Either way, you were absolutely correct and for $45 I'm back in business. Thanks for your help, Adam!
Mechanic for Honda: Adam H, Auto Mechanic replied 2 years ago
Awesome. Nothing you could have done to cause it to fail just happens sometimes. Congratulations on your repair and thanks for trusting my advice. If you need any help in the future please don’t hesitate to request me.
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Customer reply replied 2 years ago
Will do. Thanks again for your diligence and I'll give you five stars as soon as this conversation is closed. Do you do that on your side or is it something I initiate?
Mechanic for Honda: Adam H, Auto Mechanic replied 2 years ago
After I responded last I chose answer instead of info request. This should close the question on just answers end. Thanks again.
Adam H
Adam H, Auto Mechanic
Category: Honda
Satisfied Customers: 23
Experience: Shop Foreman
Verified
Adam H and 87 other Honda Specialists are ready to help you
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Customer reply replied 2 years ago
Never mind,I just discovered the closing message in another text thread and will care of it.��
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