I have a 2000 Honda CR-V (manual transmission) with almost 200k miles on it. It's using oil, and I've determined through some clues (oil analysis report, sooty tail pipe and I had to replace the catalytic converter) that the engine is running rich which is diluting the oil and causing it to burn off. The car has been meticulously maintained mechanically and we've owned it since it had 20k miles on it. I replaced the fuel pressure regulator but that didn't fix the running rich problem. My next step is to either replace the upstream oxygen sensor or start replacing injectors. I recently graphed the oxygen sensor curves using my OBD bluetooth reader and the Torque app on my phone. Can someone out there look at these curves and give me an educated opinion? Based on some reading that I did, it looks to me like the oxygen sensors are working fine. Also, based on the "Highway" graph, it looks like the graph loses its symmetry at higher rpm. You can also see some of this behavior in the "Steady State At 2500 RPM" graph. All data was captured after the car was fully warmed up after driving over 30 minutes. In each graph, the upper curve is the upstream sensor, the lower curve is the downstream sensor.

1. Does the engine appears to be running rich at higher rpms but running fine at lower rpms?

2. Do these graphs indicate that both oxygen sensors are working correctly?

3. Have any of you had issues with faulty injectors?

Thanks in advance!

Here are the graphs at idle.


Here are the graphs at idle and I floored the pedal momentarily to rev the engine.


Here are the graphs driving steady state at 2500 rpm on a flat road, approx 40 mph, in 4th gear.


Here are the graphs on the highway going approx 70 mph.


Here are the graphs on the highway going approx 70 mph and I let off the gas pedal.

 

200k on a B series, probably needs valve guides.

Doesn't look rich to me and the upstream sensor seems to be responsive. The sensor could still be biased lean driving the mixture rich. There should be long term fuel trims you can look at. See if the trims have trended positive.

 

Ryanthegreat1,

Thank-you for your reply. I've been chasing this for a while and, at the risk of information overload, here is a link to my last post which contains a link to my initial post.

This will give you the history as I've worked through getting compression numbers, looking at plugs (they don't show any burning oil) and also gathering fuel trim numbers.

According to others who have responded (and who are more knowledgeable than I), the fuel trim numbers seem to be acceptable.

https://honda-tech.com/forums/honda-.../#post52147464

 

Bump. I'm really hoping I can get more feedback on the graphs posted above.

In my limited knowledge, they all look good except for maybe this one which (I think) seems to show a rich condition.

Again, hopefully someone with more experience can chime in...

As always, thanks in advance.

 

You will get a rich condition with heavy loads. Totally normal to show rich. That is a narrow band sensor so it can really only show 14.5-14.9 and outside of that it just shows full rich or full lean.

You long term trims in the other thread appear completely normal.

I still think you are burning oil, fuel has nothing to do with it. You can melt a catalytic converter with excessive oil consumption alone. Oil = unburned hydrocarbons.

200k miles is a lot on a B series. Try going to some Rotella T6 5w-40 and driving the hell out of it for 3000 miles. That will clean up ring packs and the high loads and heat will burn out the carbon. But really it is probably the valve guides are worn out and new valve guide seals will only be a temporary fix.

 

Ryanthegreat1, I really appreciate your feedback and input.

The reason I was suspected the engine was running rich was due to the oil analysis report (see comments section in the attached pdf).

 

Worn or gummed up ring packs will cause excessive blow by. Compound problem, burns oil and dilutes the oil with fuel.

Compression check may or may not show a problem. I have had VERY worn out cylinders, like 1mm egg shaped with no cross hatch left pass compression tests and run kind of okay but consume a huge amount of oil.

 

Tying your comments below in with my initial question about a possible worn injector, I wonder if your worn rings/cylinder walls (and my rings too if that turns out to be part of the problem) were be caused by a worn injector that is dribbling fuel down the cylinder walls (versus spraying properly) which is washing the oil off of the cylinder walls.

Do you have a recommended method for testing injectors? I've read how some guys will remove them and bench test them but this seems a little dangerous if done with fuel.

 

Send them out for testing and cleaning. You will get a report on their before and after condition.

 

At this point I'm thinking a bad injector is the culprit, so I ordered a rebuilt set of injectors yesterday. I've checked everything else and nothing is sticking out as a potential problem.

My guess is one or more injectors is either spraying fuel on the cylinder wall (which isn't burning correctly and letting unburned fuel run down the cylinder wall past the rings into the pan to dilute the oil) or one is bleeding off pressure after the engine is shut off (which will pool in the cylinder, run down past the rings into the pan and dilute the oil).

To me, the black soot on the tail pipe is a sign of a rich condition versus the oil blow by that you described above.

I'm going to replace the injectors and THEN change the oil and in about 1000 miles I'll know if the problem is fixed.

I'll report back my findings, but it'll be about 6-8 weeks.

Thanks again for your help.

 

I would send out your originals and if you haven't done any maintenance to your ignition system get to it.

 

tony_2018, the cap, rotor and spark plugs are fairly new (Honda OEM parts, not aftermarket), plug wires and coil are original. Hoping to install the rebuilt injectors this weekend. I won't be able to send out the original injectors for testing first because I need to drive this car to work every day. The local shop I called that checks injectors has about a one week turn around time.