[Joseph Nowak]

I borrowed a borescope and took a look in the cylinders. Cylinder 4 had a slight wet spot on the piston, not enough to tell what it was. Pistons overall looked similar, aside from the wetness. Carbon build up was not too bad considering the 260K miles. Valves looked good with a nice tan color.
Spark plug color was a little light but these were recently changed, Cyl 4 was a little dark but still tan.

Ran compression check again and it came back as 200, 180, 165, 195 for cylinders 1, 2, 3, and 4 respectively. Still well above Honda minimum spec of 135 per the manual. The 165 next to the 195 cylinder is concerning though.

I decided to also run the leak down test to get a better idea of the condition. Results were not so great.
Cyl 1 – 56/80 – Only heard air through oil cap
Cyl 2 – 38/80 – Only heard air through oil cap
Cyl 3 – 34/80 – Noticeably more air coming out the oil cap
Cyl 4 – 56/80 – Air through oil cap and through the coolant system.

Going back to my aircraft mechanic days, I would fail this engine for a rebuild just based off of the pressures below 60 psi.

I suspect there is some leakage between cylinders 2 and 3 even though I didn’t feel anything coming out of those spark plug holes but the adjacent bad cylinders points to that.

Cylinder 4 is leaking into the coolant system which explains the wet piston.
Guess I’ll be doing head gasket over the holidays, hope I don’t have any issues with the manifold bolts and nuts.

This all make a bit more sense now, even though the engine runs great with no noticeable mileage difference, this does explain the slow acceleration which I previously attributed to just perceptual differences between the 4cyl in the CRV and the 8 cyl in my truck.

Some additional info, the misfire has not come back, the 0325 and 0420 codes did come back, so I now have 0325 (Knock circuit), 0171 (Lean), 0420 (CAT).
I’ll change the knock sensor over the holidays as it is right next to the thermostat I need to change.

Anyone have any experience with aftermarket vs OEM O2 sensors? I changed the upstream back in 2012 ( ~85K-100K ago) with a denso sensor and not an NGK/NTK sensor as it was half the price.
I changed the down stream back in January with an NGK/NTK.
CAT was done in 2015.

[Joseph Nowak]

Yea, I was impressed too, I’ve checked with 2 different compression testers. I have a leak down tester, just haven’t been able to spend the extra time required to do that test.
Before this pesky issue, the car ran great, When I moved to MD a few years ago I had to get a full inspection done for registration and the inspector even said he was impressed on how well the car looks, runs, and drives.
Most everything on the car is stock from factory, nothing has been rebuilt.
Had a front end collision in 2014 so headlights, bumper, radiator, condenser, and some other trim parts were replaced. Car suffered from the self destruction AC compressor just before that, luckily I held off on the repair so I only had to replace the condenser once.
I even think the alternator is stock (I might ave jinxed myself for this winter). The car gets regular 3-4k mile oil changes, and I even do the rear diff and transmission oil roughly every 30-40k (about every 2-3 years). The car even did a road trip from NY to Yellowstone to Anchorage and back 3 years ago. 12K miles in a month and no issues, other than 3 wind shields (1 before, during, and after).

After my last post about this issue, I ended up doing some traveling for work so the issue got pushed to the back of my mind and I forgot to continue to look into it, car ran ok. Kind of out of sight out of mind, aside from the check engine light.

I do have a update on the issue though.
After doing some research I learned that 3rd generation had a design flaw in the wiring harness that resulted, once you had an oil leak, of the FWD O2 sensor plug getting wet with oil and throwing codes, specifically 0420 and 0325. I did notice a 0325 code last week, which prompted the renewed research.
I decided to look into connection points for the emission system and sprayed some contact cleaner in a few plugs.
To my surprise I have not seen the misfire, the periodic 0420 code, or the random 0325, however I noticed a new code. P0171, system too lean.
ST and LT fuel trims are still up around the mid teens which backs that up.
I’ve checked vacuum lines again, even did the old trick of spraying things down with carb cleaner, I’m fairly confident that there isn’t a vacuum leak in the engine bay.
Car has run for roughly a week since then and no other codes show. Just 0171.

A common repair suggestion I noticed in the manual between all the codes is check/adjust the valves. I have a valve cover leak (and a thermostat leak), so I figured it could be something I could do at the same time as it’s never been done, however I won’t have the time to do that level of maintenance until Christmas week.

Anyone have any other diagnostic suggestions?
I’m traveling to see family thanksgiving week, so I won’t be able to check anything else until after that.

Thanks in Advance!!

[Joseph Nowak]

Thanks.
I’ll take a look into this.

The engine has a MAP not a MAF. I’ll dig through the manual and see if there is any component level testing. I believe the MAP values were normal last I checked, but that doesn’t tell you about intermittent or condition unique failure.

When I checked the fuel pressure last time, it was within specification, around 52 psi. I even depressurized it and started the engine with out pausing to check that. The issue was not duplicated. Holding the pressure gauge purge while running had little effect.

I’ll get some data on fuel trims while running. Though now that I cleared the code, it is going to take a little for the LTFT to stabilize as that’s a learned adjustment.

[Joseph Nowak]

I ended up pulling the throttle body off and checking all the lines last Friday. Didn’t see any issues with vacuum lines. Throttle body had some corrosion on the face where the gasket goes. Not fully on the face but enough to have me clean it up and get a new gasket. I found out the throttle drum was pretty worn and the cable was about to fall off. Got a replacement from the junk yard. Surprised they used plastic on the throttle drum but metal on the cruise control drum.

Car ran good until yesterday, maybe had a hiccup on Wed.

Mis fire code came back. 301, 304,and 300. Same sypmtoms as previously mentioned.
Long term fuel trim was +15%. Short term was 0. See picture of freeze frame. I cleared codes so I can see what the freeze frame is next time.

Any suggestions?

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• ca254634664d58d62d7f194046be1e9e

[Joseph Nowak]

No freeze frame available at the moment, I cleared the codes yesterday.
There is a pending 304 code.
I’ll take a look again once the light comes back on.

[Joseph Nowak]

I haven’t seen anything in my past checks. I did a quick once over when my wife came home, car is hot at this point. Nothing stood out.
I changed the IMRC solenoid early last year, hoses were in great condition then.

I did notice the PCV hose was collapsed while running, seemed soft while off. I attached pictures of that. The PCV is at the end of an ~18″ hose, TBH I never noticed or seen this before. I typically see them closer.
Do you think this could be contributing?

I’m off on Friday, I may spend some time doing a thorough check of vacuum lines, gaskets, manifold, solenoids, etc.

Attachments:

• b20029c0282480ad854e068593217bfe
• 7ceadbc488dc6de33cebb4a1d254e8f7

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