I am trying to decide if I have bad oxygen sensors or if something else is my issue. My mpg varies between 20 and 30. Here are a bunch of my engine parameters. Both columns are at idle. The first is after driving an hour and the second after driving two hours. I got a code P0137 after spraying off the O2 connectors with sensor cleaner. I cleared it and it hasn’t returned.
Load
ECT 55/ 63
Shrtft1 -3.9/ -1.6 to 0
Longft1 1.6/ 0.8
MAP 33/ 33-35
SparkAdv 5/ 5
IAT -3/+3
MAF 2.7(±0.10)/ 2.3-2.5
TP 14.1/14.1
O2B1S2 Both times droped slowly to 0.000 and stayed there once idling
FRP 5700(±200)/5000
O2S11 -.020(±.020) /-.020(±.020)
CATEMP11 400C/400C
Those are not OBD codes, they are engine parameters while operating at idle. Does very little to help diagnosing a bad O2 sensor, especially the one you had.
A code P0137 may mean that one or more of the following has happened:
Faulty o2 sensor
Exhaust leak near the rear sensor
Plugged catalyst
Short to voltage on O2 signal circuit
High resistance or open on O2 signal circuit
Engine running very rich or lean
Engine misfire condition
Fuel pressure very high or low - fuel pump or pressure regulator
You cleaned a dirty connector. Since cleaner fixed the problem, what likely caused the code is “High resistance or open on O2 signal circuit.” None of the other causes for that code will go away by cleaning the connector. Besides, the code hasn’t come back. You fixed it, drive on.
Right, engine parameters, not OBD codes. My mistake.
I thought oxygen sensor readings at idle were exactly how we diagnose bad oxygen sensors or see a problem.
The P0137 code wasn’t my real issue. The wide range of mpg and slight vibration at idle are my issues. I wanted to know if O2B1S2(downstream I believe) is supposed to go to 0 at idle and if the upstream one(O2S11) is supposed to jump between -.040 and 0.0 at idle. If yes then I will search for some other issue making my mpg differ by almost 50%.
The way you diagnose O2 sensors is the car setting a code telling you they have failed. OR plot the readings with time, not just state the range, plot it out. The upstream is likely a wide-band so the reading will move somewhat less. The downstream sensor is a narrow band so it will tend to be pretty level at a steady speed running down the road. It will react to throttle on and off but not as much as the upstream.
So list the codes you’ve seen besides P0137 and explain a little more the mpg and idle problems you are having.
So a steady 0.0 at idle on the downsteam oxygen sensor is perfectly normal in your opinion?
I have had my this 2010 mini cooper for about 9 months now and been replacing quite a bit on it. 78,000 miles and replaced the spark plugs, fixed lots of oil leaks, walnut blasted the intake manifold and so on. It has always gotten between 20 and 30mpg with the same type of driving style. None of these fixes have changed the mileage. One week I’ll get 20mpg and another get 30mpg. The car at idle vibrates a bit. Nothing extreme. No shakes or anything like that. Just a little vibration in the seats. It isn’t a muscle car but perhaps a little vibration is normal. I’m not sure. I changed the spark plugs because one was misfiring. They were all a bit fouled but I do not know how old they were. I’m going to pull them tomorrow to see how they look. Also, when I pulled the intake manifold some of it was melted so the car overheated at some point. I replaced the manifold. There is probably something else but that is all I can think of for now. Again, the wide variance in mileage is what has got me stumped at the moment and looking at the oxygen sensors. The car has not put up any codes besides the P0137.
No, that sensor should be about 0.45 V when operating normally. O2 is really lean or broken. Idle may not heat it up enough to read properly and the low cat temps at 400 C may be confirmation of that. Take it for a drive and see if the downstream O2 wakes up. That sensor won’t affect much else, it is there to confirm your cat is working properly. If the car doesn’t throw a code for it, it is likely OK.
THAT is a bit scary. To me that means it is time for a compression test. I strongly recommend running one. If you don’t own a tester, local auto parts stores sell them or loan them. You may have a warped head or failing head gasket. I’d also give a really good look to he wires leading to the coils as they might be damaged from the overheating.
Thanks for the information and advice. That cat temp of 400C and the downstream oxygen sensor reading of 0.0 was after driving on the highway for one hour. I don’t trust codes only as when I had a fouled spark plug misfiring the car didn’t throw a code even though a problem was obvious.
I had a compression test done when I bought the car and all was good. The lightly melted intake manifold did surprise me when I saw it but it doesn’t seem to have done any other harm.
Just adding some oxygen sensor readings from driving around to see if these are normal or not.
Cat temp between 500 and 600 C.
O2B1S2 stays fairly steady around .77 while driving, drops to 0 for a few seconds when I release the gas pedal, then jumps back to the .77 range while idling at a stoplight.
O2S11 quickly jumps around mostly between -0.1 and 0.1 but goes between -3.0 and 3.0 when accelerating or decelerating.
#1. Uneven compression in cylinders: it was suggested above and I would run it again to see the current state
#2. Dirty throttle plate or idle air control valve: easy to clean and see if it makes any difference
#3. Some kind of leak in intake system, especially considering that intake was damaged and was worked on
#4. Utility/serpentine belt. That’s a stretch, visual inspection would show if you have substantial vibration from there
#5. MAF sensor. A friend of mine chased “vibration at idle” symptom for quite some time in his Toyota Echo with 200K miles, we literally exhausted all other options, until he decided to replace MAF, car idles silk-smooth now. it was getting old probably, but not yet to the point of settig up the code. “MAF cleaner” spray did not help BTW
So I replaced all my sensors. Two MAP’s, the MAF, solenoid sensor, camshaft sensor, and two oxygen sensors.
Now I get a P129E code - Manifold Absolute Pressure Minimum Pressure Implausible.
Nothing else has changed from my previous issues. The car still idles with vibration and gets poor mileage.
My downsteam sensor reads around .80 and upstream bounces around .000
I have seen a few different things for what is the correct o2 readings of a 2010 Mini Cooper S. One says the sensors should be similar readings, one says the upstream should be around .80 and downstream between .00 and .1 and the final says the sensors should read between .45 and .50
Can anybody please confirm the correct voltages for my car. PLEASE ANSWER THIS QUESTION AS NO ONE IN THE PREVIOUS RESPONSES HAS.
Could the timing chain be responsible for any of these issues?
I appreciate the chart. My upstream voltage isn’t close to those in the graph and doesn’t bounce anywhere near that much. It stays between -.02 and .02. Downsteam is a bit closer though mine stays steady close to .80. I don’t know if voltages are different per car or pretty generic.
OBD 2 live data. The P129E code is new since I installed the two MAP sensors. Don’t think I could have messed the installation up as it is a simple screw and electrical clip.
I have also tried to measure crankcase pressure but only had a gauge in InHg. I think it reads 2.5 in idle and doesn’t move with thottle. 2.5 InHg converts to 84mbar. My car is supposed to have 38mbar crankcase pressure. I have ordered a new mannometer in mbar to try again.
One more thing. I have orangeish foam under my oil cap unless I go on long highway drives. Nothing on my dipstick though.
No they aren’t. Wideband sensors don’t have that rapid switching, that chart looks like a narrow band sensor. The 2010 Mini uses a 5 wire wideband upstream and a 4 wire heated narrow band downstream.
The 14.7:1 A/F ratio voltage for the upstream is 0.45, or Lamda =1 - some scanners can output Lamda and really that’s what you should be looking at. Less than L=1 is rich and greater than L=1 is lean
I always get confused on the downstream and upstream. So my upstream(O2S11) is around .000 all the time so I am running super lean.
What is the downstream(O2B1S2) supposed to be? .80?
I ordered the Bentley manual so I won’t have to bother asking on the forums anymore but in the meantime can anybody shed some light here why I am running super lean(I think) after replacing all the sensors on the engine. Vacuum leak? I’ve sprayed carb cleaner around the intake manifold but nothing.
Any ideas on the orange foam in my oil cap or high crankcase pressure?
The manifold pressure implausible code is probably a result of replacing the two map sensors. try putting the old ones back in, one at a time. there’s probably one of the new map sensors that’s faulty or damaged during installation (they’re pretty sensitive to electro-static shock). Are you sure your car uses two map sensors? That’s a pretty unusual configuration.
