I have a 2019 RDX with 100,400 miles. Lately the car has been hesitating to accelerate between 40-55 mph under medium throttle. No check engine lights or errors. OBD scanner shows high counts on cylinder 2 but no misfire code yet.

replaced spark plugs about 8,000 miles ago? NGK oem.

today I decided to scope the cylinders with a camera, here are the photos. First pic is cylinder one for comparison, second and third pic is cylinder 2.

Can anyone help me diagnose something from the photos? I notice more sediment in cylinder 2, perhaps fuel injector is failing?

 

Did you change the spark plugs 8,000 miles ago as routine maintenance, or did the problem already exist, and you changed the plugs in an attempt to eliminate the issue?.

Assuming there was no misfire after changing the plugs, how long after the change did the problem begin? If shortly after the change it may be a manufacturing defect in the plug.

Your next step would be to swap the coils between cylinder #1 and #2, which will only take 2 minutes. Check if the misfire moves to cylinder #1 or remains on cylinder #2.

Perform the same swap between the two spark plugs.

I'm not sure how difficult it would be to swap injectors, but that would be the next step.

You may see signs of injector problems by checking the fuel trim values.

 

Thanks for the response.

I swapped plugs and coilpacks, the high test count did not change location, still cylinder two.

I bought the car with 89,000 miles, got a misfire cel for cylinder 2 around 92,000 miles so changed plugs, since then car drove perfectly fine.

Long term trim now currently at -3.6 at idle.

i should mention I added royal purple fuel atomizer on a full tank, it was a promo from Amazon get same day delivery, I so figured why not. Prior to using the RP, no hesitation. I have about a quarter tank of gas left with this cleaner.

could it be that it dislodged some deposits in cylinder two injector and that what you see on the cylinder?

 

My own 2020 has 80,700 miles, and I get a zero misfire count on every cylinder. I still have the original plugs.

This is the second time you have noticed problems with cylinder #2. How high is the misfire count? Are the other cylinders all showing zero counts like my own, or are they just showing lower counts than cylinder #2.

It seems like you ruled out plugs and coils by performing the swaps. So that would leave the injector swap as the next test.

Modern gasoline has detergent additives included, so any cleaner you may have added, is unlikely to have dislodged anything.

Your fuel trim at - 3.6 is acceptable, and I wouldn't even look into it if it wasn't for the misfire. If anything, it does indicates the engine is detecting a slightly rich mixture. That could be caused by a leaky injector, or even a dirty air filter (which should affect all cylinders) .

Is the fuel trim better or worse at higher RPMs? How about the misfires?

I believe in the rule, "if something stops working, check the last thing you touched". Since the misfire started after adding the additive, I would wait until your tank is nearly empty before refilling with good gas, and then reevaluating the problem.

 

yes only cylinder 2 has the high test. Misfire test for that is around 40 ish. But no misfire count, I was trying to rule out carbon buildup also; but I think that would affect all cylinders.

I am leaning towards faulty injector, I’ll wait it out until this tank is finished and check again if it’s still there with fresh fuel.

 

I'm not sure what that means! I have not heard of a misfire test.

Do you mean the misfire data PID is 40, but a code has not been stored, resulting in the CEL turning on?

I understand that a code will not be set until the misfire rate exceeds 2% of all Ignition pulses.

If you simply have a count of 40, and it is not changing, then those misfires could have occurred a long time ago, and are no longer occurring.

 

Would a coolant leak cause a misfire like this?
I have no idea what the pistons on our engines should look like at 100,000 miles but those look awfully clean. Almost like they were steam cleaned or something.

 

A coolant leak could cause a misfire, but based on your previous post, I'm confused if you even have a misfire.

Please confirm if the misfire count is increasing as the engine runs? Did you know that the misfire counts are cumulative.? In other words if you had 40 misfires 2 weeks ago, and then no additional misfires since that time, the counter will continue to show 40 until you perform an ECU reset?

 

Did you buy the OEM plugs off Amazon? Many counterfeit parts out there. Have you tried replacing plug #2 with a new one?

 

here I what I mean. This photo is from cylinder two, all other cylinders have zero test and zero MIN counts. This was after resetting ecu and going around the block which triggered hesitation again.

 

Good point, that was also my first thought after I looked at my first pic which is cylinder 1. However there is no abnormal data coming from cylinder 1, I figure if it was leaking coolant there would be some misfire data in that cylinder.

Here is a pic of my cylinder 1 plug, does not appear to be whitish like it would be if coolant leaking. Plugs on all cylinders look the same as this pic.

 

I’ve restart the ECU 3 times since this has started, each time the data from the OBD increases only for cylinder 2.

 

Plugs were bought from RockAuto, NGK DILKAR8P8SY.
Back at 92k miles when I had a confirmed cylinder 2 misfire, I replaced only cylinder 2 with an Autolite Plug from Autozone. That cleared the misfire instantly and the car drove perfectly for a week until the NGK’s from RockAuto arrived.

After putting in the NGk’s I held onto the Autolite just in case.

So once this started happening I put the Autolite back in cylinder 2 but no difference in hesitation. Car has the NGK back in it now and still hesitates.

 

Well after running through the gas tank that had Royal Purple Fuel Atomizer in it and filling up with a fresh tank , the car is running like new again.

Heads up to anyone that is thinking of running Royal Purple on this engine with this mileage. You may experience symptoms like I did.

It has been 130 miles so far and zero hesitation since the new fuel.

 

I like bg44k

 

I’ve used BG44k on other cars that were N/A and port injected, no issues.

Idk, it seems like the k20c4 is sensitive to additives, or maybe that is just my experience so far. I will probably never use an additive again on my RDX.