Misfire codes keep coming back
Hello DN, hoping for some feedback, we had this fit come in with P0302 code but no noticeable misfire, I didn't have a chance to work on it myself so no scope patterns or much testing was done as customer just wanted us to install plugs n coils, which we did (not my style of doing things....but whatever) anyways next day CE light back on with all the other lights, Now we have a p0300 and p0302 as well. Scan show random occasional misfires moving from cylinder to cylinder with no drivability issues. Car is coming back in this week and I'll have a chance to check it out, wondering if there's anything I should be looking for or if anyone has encountered this issue. Plugs and coils ere from Honda. Thank you all in advance for any help with this matter.
I would check valve clearance they still use adjustable valves
These vehicles are known for carbon build up on the intake valves. Also are known for intermittent injector problems. The injectors you can run an Cylinder AF test and it will test the injectors to let you know if they are bad. I would recommend pulling the intake and checking the valves. And doing the cylinder af test. Usually I have replaced heads and injectors To fix this issue
Have you done a CKP relearn? I’ve had that happen after repair with Honda misfire codes in the past where the misfire is repaired but the code returned. The CKP relearn kept the PCM happy. HTH
Be sure the fuel is not contaminated before going far. Just a suggestion.
First thing I would suspect is valve adjustment. Usually with tight valves the fuel trims will be little negative at idle. That is from valves that open early and close late, causing valve overlap. Also can from the exhaust valve not closing completely and letting exhaust in on the intake stroke. If that is good I would be looking at injectors.
...It would have been SO EASY to do a compression test when the plugs were out...did the plug changer dude LOOK at the electrode COLORATION as the old plugs were removed (for a CLUE???)...or...just pitch them over his shoulder(so to speak) into the trash bin (bad move)...carry on...Dan H. ...South Texas...
Make sure you check oil level I had an equinox with p0300 change oil and filter misfire gone
...Richard...I think you were replying to Mauro there...Dan H. ...South Texas...
I had a slightly older Fit with the same scenario, Finally caught one of the ignition coils very intermittently failing.
Like a few others have posted, I would check valve clearance first. They are most noted when cold and will sometimes cause a stall in am until engine warms. Valves too tight.
I highly doubt its going to be a valve clearance issue. You can check the MAF & MAP sensor to verify that. Most likely it will need a set of injectors. The Honda DI cars need to have fuel induction services done every 25-30,000 miles. I would check the short term fuel trim, bad injectors typically make the vehicle run lean and can cause random misfires. If you have a good scan tool that can…
Curious about the a/f balance test i have never done one. Can you give me/us a brief overview of how that test is done and results we might see? What the test actually does and what computer is looking for thanks so much
The test Actuates the injectors in rich and lean conditions Individually. The computer is looking for the appropriate response from the sensor 1 af sensor. Then it can calculate if the injector is sticking open or not opening enough. I use it almost every day on almost every Honda that’s direct injected
Exactly what he said. If you don't have the Honda Diagnostic Software (HDS) then i'm not sure that you'll have a way to do the test.
The Autel scan tool I have can do it on most models I have tested. I don’t know about any other ones, I just have an Autel and the HDS