Misfire only on Startup

[Joseph Nowak]

I have a 2002 Honda CR-V with 1/4 million miles on it, more accurately 255K. Never had an issue with it since my Wife got it from her aunt in 2011, Her aunt bought it new.
Recently it has developed a misfire upon start up, about 2/3rds of the time on cold start. The misfire only lasts for a few seconds, longest was maybe 10 seconds. It then clears up and the car runs fine. If the engine is warm, It does not appear to have the misfire on startup. At least I don’t remember it doing so. Maybe a handful of times in the past month if it did.
While it is misfiring, if you give it throttle, the misfire is still present. Unsure if this speeds up the clearing of the misfire at this time, there is no solid evidence to support that. No issue while driving, plenty of power, MPG’s seem normal. Now for the details
I get the following codes P0301, P0304, P0300, and sometimes P0303. These are all misfire codes and I have followed the Honda Service manual for the standard diagnostics and everything seems good.

Here are the results of my tests/diagnostics in no particular order:
– Cylinder Compression: between 185-200 PSI on cold engine (Min spec 135)
– Fuel Pressure: 52 PSI (Spec 48-55)
– Moved around coil packs, misfire does not follow the packs. I even bought a couple packs and installed them to see if it’ll fix it with no luck. Returned the coil packs.
– Moved around Spark Plugs, misfire does not follow the plugs. I ended up changing them anyway as its been ~40K since changed.
– Injectors Ohm’d out good, when I pulled them they seemed a bit dirty and I had a coupon from Advance so I changed them out as they were original.
– I read out the wire harness for the Coils and Injectors back to the ECM. Resistance was nominal, no opens or shorts.
– I ran a can of Seafoam through it to clean the combustion chamber. Everything was normal, no Change. (Was not told by the manual to do this, I just had a can in the garage and figure I’d give it a shot)
I have put gas from different stations in it, Ran a tank with fuel system cleaner so I don’t believe it is a fuel quality issue.
Though strangely I did not have the misfire when I spent 5 days in NY visiting family over the 4th. But the after day we got back in Southern MD I noticed it on the first start up. Maybe its just a coincidence. I’d hate to have the issue being PAX NAS is doing some EW testing and inadvertently affecting my vehicle only. Highly unlikely but funny to think about.:P

The only thing I have not done that the Honda Service manual said was replace the ECM.

Usually I can handle any issue’s on vehicles but this one has gotten me stumped. Either I am over looking something simple or something major has happened that I am not familiar with.

I am thinking of cleaning the throttle and IACV. I may go in and adjust the valves, with 255K miles, I’d think they are a bit off.
I’m not afraid of doing any repairs to the car. I was an A&P from 09-14 and I have worked as an engineer since 2014 (I’m not your typical engineer that has no understanding of actually performing maintenance! 😆 ). I have also been working on cars for maybe 15 years.
Any help would be appreciated!

Thank you.

Topic

[Richard Kirshy]

Have you checked for a vacuum leak when the engine is cold started??
Sounds like it could be Leaking from after the MAF.
Throttle body or intake.

[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.

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[Richard Kirshy]

[size=4]Might be a good idea to look at your fuel trims.
If you get a SES due to miss fire, the freeze frame data could provide direction.[/size]

[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 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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[Richard Kirshy]

I realize that this FF data.
Though to get a more accurate fuel trim reading it really needs to be in open loop
If your LTFT is at +15 %, then that indicates that the fuel maps were about 15% lean, and the ECU adapted by enriching the mixture by 15% to become happy. Since the LTFT has stabilized, your engine is no longer running lean.
In a perfect world LTFT would be zero and STFT will range from + / – 5%
But now days with most fuel having 10% alcohol, that changes things a little.
Also engine wear can also play a part.
Now considering these misfires only occur within the first 10 seconds after start up.
It could still be a lean condition.
If there are no signs of a vacuum leak or faulty MAF sensor.
Might have a look at the fuel delivery setup.
One test,
On a cold start , cycle the key several times to the ON ( NOT CRANK / START ) position and allow the fuel system to pressurize.
The start the engine and see if the misfire is still present.
If it does not misfire on you after several cold starts ( yea I know, it will take a little time to prove or disprove this )
You’ll need to hook a fuel pressure gauge on to the fuel rail and see if the pressure is up to specs.

[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.

[John Gotti]

Did you ever figure it out?

[Its me]

I think your issue is in the cylinders.

The number I am keying off is your cylinder compression. Was this engine rebuilt?

Seeing 185 to 200 PSI is absolutely incredible for an engine with 250k + miles. I would expect to see 130-150 for an engine with that many miles…

Are you absolutely sure about that number? I would do a cylinder leak down test anyway. When done properly, they provide excellent data.

JMHO

Karl

[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!!

[Jamie Owens]

Here was my “misfire on startup” issue and resolution https://www.ericthecarguy.com/kunena/8-Service-and-Repair-Questions-Answered-Here/49955-1997-honda-accord-f22b1-misfire-cyl-2-code-p0302

[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.

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