2002 Honda Accord LX 3.0 V6 240k miles

One day suddenly started riding very rough, vibrating. Received misfire codes for all cylinders besides 6 (P0300, 301, 302, 303, 304, 305) and a code for a P1399 which says it could be for a cylinder head, head gasket, or fuel injectors. I replaced the spark plugs approximately 2 or 3 years ago. I still pulled one of the spark plugs and looked at it, looked good. EVAP cannister replaced approx 1 year ago. EGR valve done somewhere around that time as well. New radiator placed within past year too. Did an exhaust in coolant test (the liquid that turns from blue to yellow), negative for exhaust gasses. Bought a new ignition coil and swapped it for cylinder 1, still received misfire code. Cleared the codes and took the ignition coil out of cylinder 6 and swapped it with cylinder 3. Started engine w/OBD2 attached and revved to 2500 rpms, maintained this until codes thrown again. At that time I got misfires on cylinders 2, 3, 5. Fuel injectors? Fuel pump (I have not taken this out to look at it yet; as far as I know never serviced)?

Thanks for any ideas/insight

 

Before replacing any parts, use your obd2 scanner to read some live data. Guessing at what is wrong and throwing parts can complicate the diagnosis. I've seen many new aftermarket parts fail out of the box.

Get the engine to operaing temperature. Look at the short term and long term fuel trims for bank 1 and bank 2, so four pcm data pids total. Let us know the fuel trims at idle and then at ~2000 rpm, so 8 data points total.. The trims jump around a bit, so an approximation like 18 will work for this testing.

 

Okay, will do. Thanks for pointing me in this direction. It’ll have to wait until tomorrow evening, once I’m done work, for me to have a chance to get the info.

 

Okay, here's what I got:

Idle
STFT1 = 6
LTFT1 = 0
STFTB1S1 = 6
STFTB1S2 = 6

@2500 rpms
STFT1 = -2.77
LTFT = 0
STFTB1S1 = 1.55
STFTB1S2 = -1.95

I'm very uninformed on how to interpret these numbers so I hope this helps and thanks.

 

On a V6, you add short term and long term fuel trim on each bank to get total fuel trim. So bank one is cylinders 1,2, and 3. Total fuel trim <10 is good.

You are missing bank two, so cylinder 4, 5, and 6. Do you have an option for STFTB2S1 and STFTB2S2 or something for bank 2 (STFT2/LTFT2)?

This is showing how much fuel is added or removed to maintain the proper air fuel ratio accoring to the O2 sesnsors. If you were running very lean, then you could have a vacuum leak or too little fuel/fuel pressure. So far that doesn't seem to be an issue at least on bank 1.

Is the engine running poorly?

 

Two videos. Had to split because of file size. These are the only options I have on my OBD2. Could there be some problem with bank 2 sensor? Yes, engine is running poorly. Vibrating and rough idle.

 

Problem uploading videos. I’ll take screenshots.

 

 

For context: these screenshots are from the 2500rpms time. These are the only screens I have available for live data.


Oh duh you can see that on the picture.

 

Nothing looks way off in the numbers. The computer may not report certain data when codes are set, so you might want to repeat after clearing the codes.

I'm trying to think of items to check. You could pull off the vacuum hose to the fuel pressure regulators and look for a strong smell of gasoline.

Any chance you filled up the gas tank not long before the misfires happened?