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Stuck open EGR will cause power loss and misfire on idle as well as higher than normal MAP reading.
I am suspecting AFR sensor shifted rich (although in many cases it shifts lean).
Is that what you gather from my pictures?
I am familiar with egr operation and common problems associated with it, just not the live stream data. I don't know what egr err % is and what normal values are. (Edit- looks like many people get the 99.2% egr err. Mine has been 0%, 50%, and 99% during the pictures I have been taking, so I think it is ok, seems to be moving)
So, aside from my visual inspection, is there any test I can run on the o2 sensor, or is buying a new one and trying it out my only option?
And I feel like my car is in fact running rich. You can smell ot sometimes and my gas mikeage is pretty bad. 60% of a tank gone in 140 miles.
The gas mileage is not that horrible 250 miles on one tank yields about 25 mpg, which is not uncommon for stop and going; I am making 28 MPG.I would install oem air filter housing with dry type air cleaner element and try to substitute AFR sensor with known good one.
bad smell may come from dying catalytic converter, oil and fuel additives.
Well, I've been driving around with the engine light on. No changes in how it drives. If the light wasn't on, I wouldn't think a thing. I finally got a fuel pressure test done and it checked out ok at 52psi while running.
I haven't replaced the O2 sensor yet. I guess that's next. It does smell like it is running rich. My brother, who also is a mechanic, said that to me after I drove away from him and I've never even told him about the problem. I'm still kinda of wondering if some weird modification was done for performance by the previous owner, but the live data stream looks normal, or so you guys have said.
Anyway, I just wanted to put an update out there. I'll probably try a new sensor soon.
As a side note, I checked freeze frame for 05 Pilot with pending code P0172 for one bank only; at this time MAP reading (idle, no load, 900 rpm) was over 42 kPa which may trick computer for injecting more fuel than needed.
For this particular car, out of adjustment valves cause abnormal MAP reading, extra fuel and rich code
So, a bad o2 sensor would create a false reading, but I think the car is in fact running rich. But the computer is correcting and trying to take away fuel. So what would actually create a rich condition at all times? Perhaps a leaky injector? The car just runs so well. I have absolutely no performance complaints. In fact, I feel like the car is much faster than I expected from a little, 105hp, motor.
Leaky injector will actually create miss, especially when computer will try to cut injection time for ALL injectors (leaking one will spray more than enough in one cylinder others 3 will spray less)
I hope no one changed injectors for high flow or such
excessive amount of oil vapors (from PCV) or stuck open vapor purge valve (which you ruled out already) could be other reason.
Leaky injector will actually create miss, especially when computer will try to cut injection time for ALL injectors (leaking one will spray more than enough in one cylinder others 3 will spray less)
I hope no one changed injectors for high flow or such
excessive amount of oil vapors (from PCV) or stuck open vapor purge valve (which you ruled out already) could be other reason.
I've never used this on Fit, but this test may work.
Warm the engine up and unplug AFR sensor (this will disable ECU ability to correct the mixture)
Check the idle speed- if mixture is rich the rpm will be higher than normal, and the car may emit rotten egg smell from exhaust
Increase RPM to 2500 and release gas pedal if it runs rich, the rpms will drop below idle the engine will sputter then recover
drive car around for 5 minutes in 4 th gear keeping rpms below 2500
shut the engine off , pull the plugs out and inspect for carbon deposits on the base of side electrode. Look for difference among the cylinders! I am trying to find values for the current generated by AFR sensor during normal condition, but in your case the engine runs with optimal mixture after ECU made necessary corrections for extra fuel
I got this code when I disconnected air temp sensor immediately after turning ignition off. So there could be some bad contacts between sensor and its wiring. Rarely, defective (open) sensor can be the cause. This will cause mixture enrichment or rather larger compensation form ECU to correct rich mixure.
On my car, after it is switched off hot, the IAT sensor reads 48 degrees C; when engine starts the cooler ambient air cools the IAT sensor and it reads cooler temps. So, my STFT is +8% at the beginning but goes down to +/-2.3% at idle
SO, I pulled the o2 sensor wire off, cleared codes, ran around for a few days. It performed the exact same. Pulled the plugs after a couple days of driving and they looked perfectly normal, so I have a new o2 sensor coming in the mail to try out.
Though I really thought it smelt rich, I had forgotten that I had put injector cleaning in the gas. It may have been that. (Which I believe you pointed out Doc)
Because I am still not sure if AFR sensor was the probable cause I would rather get a good used one if possible just for testing (it costs here $25 at pick your part; don't have to be exact application as long as it is off Honda 2007-2008, same thread and same connector wire; length is is not very important).
When I was working on 2000 Corolla with P0171 (lean) code, which is typically MAF sensor failure, well documented in many cases, I was misled by its reading on idle (it was in the specks, according to the manual). In addition, despite same pin-out and internal design, the connector on this only sensor (Corolla and Prism)was positioned at 135 degrees angle (all other Toyota applications had straight connector).
Nevertheless, I went to the wrecking yard and pulled "good used" (marked up) sensor from 2002 Echo (with straight connector ) and tried to fit it on Corolla found at the same yard. To my surprise it went right on; there were no issues connecting harness to it and/or attaching it to the air cleaner box. So I grabbed this sensor, installed it to the car I was working on and the problem was fixed (confirmed by scanner STFT reading).
The original sensor had broken resistance wire which I was able to see under 10X inspection scope.
Sorry for off-topic
Good luck!
Well shoot, after buying an aftermarket Denso sensor, I pull off the old one to find out that it is the exact same denso sensor.
Right at startup things looked good, but soon the stft was back to -31. I felt like it was a little better? Rather than pegged at -31 it was only at -27 while cruising some.
according to the service manual it said if at 3k rpm, held until the fan kicked in, it should cycle. Well, it did cycle, but all above .6v.
Do I try yet another sensor, or something else? Driving with the sensor unplugged my plugs looked good. Maybe I should check them with the sensor in and -31 stft and see if they look lean?
Here is idle at full temp after installing the new sensor.
With electrical connector unplugged from the valve (on the top of throttle body) and the hose removed from the black metal pipe there should be no vacuum felt at the end of the pipe with engine on idle (valve should be closed)
03-07-2017, 07:18 AM
