I think that having too much oxygen in the exhaust would cause the ECU to make the fuel trim be too rich. The ECU will see to much oxygen and add fuel to burn the extra oxygen (up to a certain point).

I would think that any leak will fool the O2 sensor, but I don't know to what extent.

 

yeah, you normally don't want more than +/-10%, all though i believe you can go as far as 20-25% before you set a code. the honda scantool doesn't display % for fuel trim normally, it shows the decimal(1.00) instead.


extra air inthe exhaust can affect the reading. but typcially exhaust is coming out the leak, not sucking air in it. so i'd still think it's running slightly rich(caused by high fuel pressure which is caused by a bad fuel pressure regulator or clogged/pinched fuel return line, a bad or lazy o2 sensor or a leaking evap purge control solenoid or misadjusted valves, etc)

 

Based on the fuel trim numbers, I agree that it's running rich. I suppose that could explain the performance problem but now I have to figure out how to diagnose the cause of it running rich.

The valves were all slightly tight by .002-.005 so I adjusted them but didn't see any improvement.

I would expect a problem with the evap system to set a code.

I'll have to check the high fuel pressure possibility. Any hints on how to best do that?

The O2 sensor should be pretty easy to check but since this has a wideband sensor, I wonder if there's a different procedure for it.

There's also the possibility of using mode 06 data from OBD-II. If I recall correctly, the status for $05 was LOW. As best as I can tell, that's a calculation using the secondary O2 sensor response to fuel input.

I appreciate everybody's help so far. Hopefully we're getting close to resolving this.

 

for some reason i thought this was an 03. 2002 uses regular o2 sensors. you should be able to view the live data on your scantool. if it doesn't update fast enough you can use a dmm and view the data.

hook your positive probe to the white wire and the negative probe on the light green wire. you don't want it to stay below .3v or above .6v too long. hold the rpm at 3000 rpm. is it switching fairly fast across the .45v threshold? if you raise the engine rpm rapidly at full throttle you should see the reading spike to .8v or .9v, and then when you close the throttle and let the rpm fall from redline it should spike low to .1v or .2v.

if it appears lazy replace it.

i've had bad/sticking/leaking pcs without evap codes. the check is simple - apply vacuum to the manifold side of the solenoid while manually energizing the solenoid and tapping it lightly. you want to do it more than a few times trying to catch it in the act.

was $05 the TID or CID? it depends, since $05 is both a TID and CID for the CAT, primary o2 sensor andsecondary 02 sensor.


as far as fuel pressure goes, hook up a fuel pressure gauge. that's the best way and only way to check if the fuel pressure regulator is stuck closed or something.

 

Here's what my scan tool recorded for $05Based on that, I'd interpret $05 as the TID

 

I have the ULEV motor and I thought those used a wideband sensor in the exhaust manifold. If that's the case, it might explain the strange results I got from my meter. It was reading around .300 V and didn't go lower than .165 V or higher than .365 V. That didn't seem right so I hooked up my scan tool to see the live data and it was reading in the neighborhood of .680 V but not fluctuating much.

The discrepancy in the readings got me to wondering so I recorded some data to try and visualize what was going on. The graph of the O2 sensor data and engine RPM is attached. The areas where you see the drops in the sensor voltage down to .005 V are where I felt the engine stumble and drop by about 200 RPM each time. It only seemed to happen at 5000 RPM. You can see later where I got up to 4500 RPM and didn't see that drop or feel a stumble.

I also noticed a clicking sound at idle coming from somewhere in the neighborhood of the intake manifold. A bump on the throttle made it go away but it comes back after a few moments at idle.

It feels like I'm taking two steps backwards here. Any ideas?


[IMG]local://upfiles/14036/F241771958B64648906D525458842342.gif[/IMG]

 

CID 01 TID $05 isa CAT test. p0420 is the result.

 

nice graph, that reading is the primary sensor and it is reading slightly rich. that 5000 rpm spike looks like fuel cut was engaged causing the lean spike. the clicking noise is most likely the purge control solenoid - normal.

 

Running rich would lead to the low performance and reduced gas mileage. I guess the question now is why is it running rich and is that contributing to the P0420 code or are they two unrelated problems.

 

What would cause the fuel cut?