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The reason I mention reset is that while the engine is idling the short term Trims will set back to zero and then slowly move back. The engine will momentarily smooth out and then move back to missfires. And this happens over and over and over.
Any Check Engine Light codes with the OBD - 2 basic reader ?
Your reader that is giving you live data like your fuel trims as observed
Your reader probably has other parameter IDs ( PID ) that can be looked at
The 4 most important are:
Mass air flow rate
Throttle position sensor
Engine coolant Temperature
and your STFT
At idle for this engine the values are :
TPS : 13 % at idle and moving very smoothly toward 100 at wide open throttle
MAF : 4.5 grams / second at correct idle going up to around 175 on wide open throttle
ECT : at least 88 C after warm up
STFT target of 0 %
Without the reader you can use a common multimeter
With the reader you can record a graph so when at home you can interpret you live data and see what is the cause of your drift
There is a thing if the ECU sees a sensor missing or out of expected range it will reject the sensor and revert to a not optimal set of data maps or arrays until that sensor comes back in range
This takes some time to default back and forth out of best engine regulation
Before I threw parts at any other sensor, I used the live data when I bought this car to observe Open loop heavy components such as the Coolant temp, mass air flow sensor and throttle position to indicate if either of those are a fault.
apon viewing the live data 20 mins ago, everything was reading complete nominal and in range. HOWEVER,
before leaving into my gym I hooked up the code reader and read the codes. At idle, this is what they read, STFT B1 0% (GOOD!!) STFT B2 +24% (NOT GOOD) it has been running much better after fixing an exhaust leak and egr leak but still missfired a little and a weird flat loss of power. So, I reset the ECU and turned the car back on.
The fuel trim for bank one was back to -24 and the trim for bank 2 was +24. And it ran noticeably much worse!
also to note, they both rose completely parallel of each other I,E if bank one was -10 bank two was +10 and so fourth up to 24 where it held This is when i plugged it in before resetting After resetting
On paper 192 F is very very near the tripping point of open / closed loop mode 88 C
The fluid thermostat should hold it a slight margin above the tripping point
So you might be at a thermostat change keeping in mind the thermostat does not take a large O - ring even if it comes with one , cracks the housing on bolt down
You might observe if the ECT waviers below your 192 shown as this would be worse
STFT should be constantly jumping around. If you have a static number, something is wrong.
Coolant Temp needs to get to 160F or 170F (I forget) before engine can go open loop. Your coolant and it's sensor are in the clear. Cross that off.
If I had to throw a part at this, it would be a new crankshaft position sensor. They are fairly cheap online and you can replace it in about 15 minutes.
I actually just changed my CPS last night with, of course, no change in operation. All connections to the ECU are clean and in good condition. I even opened up the ECU case to check all the Caps and soldier Connections for cracks and or corrosion. Everything looks great, PERFECT even. So I'm still at a loss.
You mentioned that the oxygen sensors had been replaced as well. Can you read them on your OBD2 device. Like the STFTs, they should be constantly moving. If theres a number that is static, thats a problem.
All four of your oxygen sensors have the same plug. When they were last replaced, is it at all possible that they were switched accidentally? There is no absolute way of checking, since a PDU/WDS can have the ECU "relearn" the orientation of the oxygen sensors. BUT if no one has ever performed that on the car, the following would be connected:
Bank A Upstream has a solid GREEN wire (along with Blue/Purple, Blue/Brown, White/Brown) - The Bank A Downstream has a solid BLUE wire (along with Blue/Purple, Blue/Pink, White/Brown)
Bank B Upstream has a solid BROWN wire (along with Blue/Purple, Blue/Brown, White/Brown) - The Bank B Downstream has a solid RED wire (along with Blue/Purple, Blue/Pink, White/Brown)
Make sure you trace the right sensor wire back to the connection and check these wire colors against what is connected. I would mark each side of the harness and only then, see what happens where you swap out upstreams, then downstreams.
MAF sensor could also be to blame here. Have you tried cleaning it, and checking connections? They make a MAF sensor cleaner spray....
The instrument gauge temp indicator is the single wire temp sensor on the thermostat housing
The ECT sensor to the ECU is the 2 wire sensor next to it
Since you have a wide variance on your device that the ECU is seeing at different times you can in this case compare the temps with the inaccurate instrument cluster for a correlation of what state your cooling fluid actually is
I'm going to stick with 88 C tripping point even though I can't find it documented
Vee had the suggestion of giving a slight twist in the MAF sensor connector pin / blades for better contact so it does not " drop out "
Revisit what b1mcp said. Swapping the O2 sensor plugs and getting them in the wrong sockets is very easy to do, and would seem likely to produce the sort of symptoms you were experiencing.
Alright, The MAF is not the problem (I'm observing how it meters air and everything looks correct)
As of now, LTFT for both banks is -10.5
STFT for both banks are flip flopped. If bank one is -24 then bank two is +24. Under WOT they both set to 0.
voltages for b1 and b2 lamba sensors are between 1.00v and 0.985v on both banks (fluctuating)
normally, i see 185 degrees from the ECU when the dash Temp gauge reads one Tick below "normal"
coolant temp sensor new, all new coils, injectors are good, no smoke leak when leak down tested, Crank position sensor is new.
b1 is always taking away fuel and b2 is always adding in some variety or another