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Discussion Starter #1
So I just picked up a 2006 Honda Ridgeline with 236K miles and the CEL on. Pulled P0302 (misfire on cylinder 2). Popped the hood and every single coil looked like it had gone 10 rounds with Mike Tyson. Replaced all of the coils and plugs and cleaned the EGR valve, no more P0302.

I checked the air filter while I was there, it wasn't too bad so I just put it back, but now I am getting both P0172 and P0175, which makes me think I rattled something loose when I was checking the air filter.

I hooked up my bluetooth OBDII adapter and fired up Torque to log out the AFR and ran it until the CEL came back on the VTM-4 light came on to indicate a problem. However the ECU never logged an AFR higher than 14.5:1. As this is only 0.2:1 off from the nominal 14.7:1, I can't help but wonder if that is really enough to cause it to throw the error?

I tried opening up the air filter box again and cleaning everything out, but it is still throwing the code. It does seem to idle rough sometimes, but no more than I would expect from a high-mileage truck and not in conjunction with the code being thrown. It never bucks or hesitates during acceleration and I don't get any smell off the exhaust like it's dumping too much raw fuel through the catalytic converter.

Anyone have any ideas? It was both banks and at the same time, so I don't think it's a sensor as both banks have independent sensors, it has to be up-stream from there somewhere, right?
 

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1. Some emissions-related codes will disable VTM-4 system which is why you're seeing a VTM-4 light. Don't worry about that - it's normal.

2. 14.7:1 is the stoichiometric ratio for a gasoline engine, but the PCM will command richer or leaner depending on conditions.

3. Possible causes of P0172 and P0175 (banks 1 and 2 too rich) are a MAF sensor and a fuel pressure regulator.

UPDATE: Disregard - this information applies to the 2009-up Ridgeline. The 2006-2008 does not have a MAF sensor.
 

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Discussion Starter #4
LTFT Bank 1 hovers around -14.8%
LTFT Bank 2 hovers around -15.4%

variances are +- 3%

Numbers are the same at idle, 1500, and 2500 rpm under no load and under load.

If anything I am just more confused now since people are saying this could be anything from a bad spark plug (even new plugs can be bad, not ruling anything out), to a multitude of other things.

Cleaned the MAP sensor and replaced the air filter since it needed to be done anyways, but still haven't seen anything change.
 

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Discussion Starter #5
Never mind, second round of cleaning to the MAP sensor cleaned everything out.

I felt it bog and the CEL came on when I started it up, and when it cleared up the LTFT for both banks was -.08% steady under all conditions.

Thank you much all!

For future reference for anyone else, this is the video I watched to learn how to clean the MAP sensor:

 

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Discussion Starter #6
Well, unless someone has some other suggestions on things a shade-tree mechanic like me can try, I think I'm going to give up and take it to a mechanic.

It threw the CEL on again, same codes.

Monitored both the short-term and long-term fuel trims.

LTFT for both banks sits around -18% fairly steadily
STFT for bank 1 sits around -17% but trims out to -4% @ 3000rpm
STFT for bank 2 sits around -18% and trims out to -6% @ 2000rpm but goes right back to ~-18% @ 3000rpm

For some reason my diagnostic tool is not able to pull a reading from any of the O2 sensors or I'd have a complete picture of what's going on.

Unplugging the MAP sensor and plugging it back in always results in a reset to ~0% across the board, so I guess my previous experience was just a placebo.

The weird thing is, it runs fine until it thinks it needs to adjust the fuel trims all crazy. During the reset right after unplugging the MAP sensor and plugging it back in the truck runs 100% smooth, plenty of power, no shuddering, jerking, or hesitation. Nothing. And then for some reason the truck seems to think the end of the world is coming and FUBARs the fuel trims and everything goes to hell in a hand basket.
 

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Please review the link I pasted earlier. Look at trouble shooting MAF and MAP sensors. On your scanner with the engine running look at air density and perform the "truth test." I would suspect one of these sensors.

However with as many miles on your vehicle and he lack of maintenance you reported, the MAP sensor maybe reporting low vacuum conditions due to engine wear etc. Take actual vacuum readings and see. (When was the timing belt done?) Head or intake gasket leakage etc.

Look at fuel pressure readings and insure the fuel pressure regulator is performing properly and not sticking.

And yes if not sure take it to a garage that you trust. I have used the unplug the sensor and observe the response before as a last resort. The ECM on some earlier models will use substituted data when the sensor fails. If the engine runs better with the sensor unplugged then this points to probable failure.

Good Luck and God Bless
 

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Discussion Starter #8
Sorry to dig up an old thread, but I just wanted to post the conclusion to this. The previous owner had tried to do a valve adjustment and had actually done it completely incorrectly. Some of the valves were actually seized shut causing it to sound like there was a vacuum leak. After a valve adjustment LTFT is -8 for bank 1 and -6 for bank 2. For a vehicle with 246,000+ miles on it I find that to be plenty acceptable.
 

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Sorry to dig up an old thread, but I just wanted to post the conclusion to this. The previous owner had tried to do a valve adjustment and had actually done it completely incorrectly. Some of the valves were actually seized shut causing it to sound like there was a vacuum leak. After a valve adjustment LTFT is -8 for bank 1 and -6 for bank 2. For a vehicle with 246,000+ miles on it I find that to be plenty acceptable.
Thanks for the follow up, and best of luck for many more miles. :grin:

This will be helpful for determining shut valves & the importance of a proper valve adjustment
 

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Glad you got it fixed! I missed this one the first time. Reading it this AM, I was thinking ‘adjust the valves.’ Glad you did!
(-:
 

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Sorry to dig up an old thread, but I just wanted to post the conclusion to this. The previous owner had tried to do a valve adjustment and had actually done it completely incorrectly. Some of the valves were actually seized shut causing it to sound like there was a vacuum leak. After a valve adjustment LTFT is -8 for bank 1 and -6 for bank 2. For a vehicle with 246,000+ miles on it I find that to be plenty acceptable.
Unless you heard that the previous owner did the valve adjustment wrong, i wouldnt be so sure it was him - ridgelines have a knack for seizing some valves shut.

Do you the mileage when he did the adjustment? Im trying to find out the interval over which the valves shut again.

Glad you figured it out and I hope this serves as further warning for people to check their ridgeline valves.
 
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