I've had a persistent issue for some time with my Accord that, for the life of me, I cannot figure out. If anything, the symptoms listed below have become more acute.
Issue(s):
Primary Codes (i.e. come on with every CEL reset): p0301, p0302, p0303, p0304, p0305, p0306, P1399
Secondary Codes (i.e. sometimes come on after CEL resets): P0507, P0421
Symptoms/Characteristics:
- Rough idle at startup (particularly bad when the weather and engine are cold);
- will go away almost all of the time when the engine is warm.
- Rough idle is more acute when the car is in gear; not as severe when in Park or Neutral.
- Get the blinking CEL (i.e. misfire), particularly when coasting at speeds at or below 40 MPH - BUT I don't feel the engine shudder of a cylinder misfire.
- Will also happen when coasting in Neutral (the idle RPM issue, below, also can occur in Neutral when coasting).
- The engine, when accelerating or at cruising speed, feels completely normal, particularly when it's warmed up.
- At idle, RPM range fluctuates wildly (250-1000 RPM); engine shudders at the ~250RPM low range)
- Particularly bad when the A/C compressor is running; at times, it will maintain a steady RPM but below the standard ~750 RPM
- It can be at the normal (750 range), especially when the engine is warmed up
- The fluctuating RPM doesn't pop a CEL.
- There's been a few times, very recently, where the engine stalled in these conditions.
- Poor MPG (normally will get 360+ miles p/tank - currently getting 280-300 miles p/tank)
- The engine has been underpowered when going up inclines in CO (i.e. pedal to the floor)
Work done to date with no improvement in symptoms:
- New Spark plugs (all 6)
- New ignition coils (all 6)
- Replace the Idle Air Control valve (FWIW, not replaced with a Denso OEM part due to supply chain issues)
- Replaced spark tube & valve cover gaskets (they were leaking oil)
- Tested alternator (a bit on the low side, 14.0-14.1 Volts)
- Timing belt only has 40K on it.
Thoughts, Ideas? Anyone with prior experience with this in their v6, J-series Honda engine?
Update from this evening:
Conducted a compression test (just a dry test this evening). All 6 cylinders came out between 145-157 PSI. So far, so good.
With pulling the spark plugs out, I looked at them. Nothing looked abnormal on the tips, which is what I would expect after replacing the leaky spark tube seals and valve cover gasket 18 months ago (photo included via link - https://photos.app.goo.gl/WgRK6QsHi7nWmdd78 ).
I can't do anything else tonight given how late it is, bilut with consistent results across the 6 cylinders (difference of 7%, within accepted range), is there any reason to do a wet compression test?
My understanding is that wet compression tests are needed when a cylinder is identified with having too low pressure.
I don't believe the valves have ever been done in the car's history
it's in the owner's manual. Every 100k miles.
Do a wet and dry compression test on all cylinders. If the motor needs replacement, then junk the car because it's not worth replacing it on a 22 year old car.
I can certainly see if I can do a compression test, although I would be shocked if the engine is bad, given I've taken good care of it for the 12 years I've owned the car (and the J series engine is incredible).
I can certainly see if I can do a compression test, although I would be shocked if the engine is bad,
Better to be sure. If there is an internal engine problem nothing you do externally will help. A lot can happen to an engine in 22 years.
Bumping this forum up to to see what I should look at next since we know compression is good.
FYI, did a quick test on the IACV by unplugging it. RPMs surged, as they should have.
Scotty,
I posted here previously, but the thread kinda died out. Go here for a recap of the symptoms/issues.
I bit the bullet and decided to bring it into a Honda dealership for a diagnostic. After a bit of back-and-forth (when I pushed against their rudimentary reading of the codes "oh a misfire? Let's replace the spark plugs and coils - again"), they returned the following:
- FOUND THE MAP SENSOR VOLTAGE IS HIGH, POSSIBLE ENGINE VALVEAS ARE TIGHT. WOULD NEED TO CHCK AND ADJUST THE VALVES.
- CHECKED THE TIMING BELT TIMING AND POSSIBLE IT OFF TIME. WHEN THE CRANK IS ON TOPP DEAD CENTER MARK BOTH CAMSHAFTS ARE FOOR BTY ONE TOOTH. WWOULD NEED TO REMOVE THE COVER TO VERIFY (I think he meant to write "off by one tooth")
Part of me feels like $1000 for a "maybe this is the issue?" However, I will say, I don't believe the valves have ever been done in the car's history. From experience, do the symptoms/issues I describe seem like they could be caused by a timing belt (potentially) being off by 1 tooth?
Please don't post multiple times about the same car problem. It's against forum rules and makes it more difficult to follow the progress of a particular issue. If you want to move your post up to the top for more attention all you need to do is post a response in your original thread. Thank you. (Topics merged.)