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Old 05-07-2019, 07:39 AM   #1
CelicaTom
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Mixtures of running extremely Lean & Rich

Hello Everyone!

I'm hoping someone can help me, or at least point me in the right direction.

I'm having problems with my celica VVTLI 190 - UKDM (GTS)

Cutting a long story short, I'm having problems with a misfire on idle (due to lean running) and very poor mpg and performance from my 2ZZGE.

I have replaced and checked every common sense sensor associated with this issue.
  • Coil Packs
    Spark Plugs (x3 sets)
    Injectors
    O2 Sensor
    MAF
    Crank Position Sensor
    Cam Position Sensor
    Thermostat
    Temp sensor
    Air Filter
    IACV

I do not have any vacuum leaks, and I am not running an induction kit.

The car is only light modified, I have a 2.5" custom de-cat exhaust and a light weight flywheel.

I recently had my car dyno'd, it came out at 166hp at the fly. under 3k rpm the car runs 18 AFR, as soon as it hits 3k it turns so rich the wideband probe cannot register how rich it is. (past 8 AFR).

I have checked and double checked the timing and its 100% correct.

I regularly get the misfire codes coming through on the ECU (P0300 - P0304) They are the only codes I get.

Could somebody point me in the right direction as to what the problem might be? I'm really running out of idea's so any help at all would be really appreciated.

Thanks guys!
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Old 05-07-2019, 10:21 AM   #2
2way
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Time to look at live sensor data or at least pull the freeze frame data.
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Old 05-07-2019, 01:28 PM   #3
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100% sure you have no exhaust leaks?
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Old 05-09-2019, 01:58 AM   #4
CelicaTom
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Thanks for the replies,

Exhaust is solid, the only place I need to check is where the manifold (header) bolts to the cylinder head, but I doubt there is an issue.

The cylinder head has been replaced with one from a corolla, with new valves, steam seals and all gaskets replaced after the car was mis-shifted and bent some valves. (so I've basically touched everything in the engine bay)

I'm going to try JDM ECU and see if there is any change. If not I'll be taking it to someone who can log the data and go from there.
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Old 05-12-2019, 10:24 AM   #5
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Is there an issue with actual fuel delivery?
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Old 05-16-2019, 11:21 PM   #6
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Any chance you can test a different ECU (assuming you have not already)?
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Old 05-17-2019, 07:36 AM   #7
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A couple of things that pop out right away is first you're throwing parts at it but not performing any diagnostics. Test the sensors before you change them so you're not just throwing money away.

Second, once your sensor has failed an actual diagnostic test check the wiring harness and connectors. You may have been holding the cause in your hand and never known without proper testing.

Third just reading your symptom list my primary suspect was throttle position sensor. There is more in there than just a position sensor variable resistor. There is a closed throttle switch and a wide open throttle switch. So what if it says your wide open because wo switch is stuck closed? Well at actual closed throttle there will be some conflict at partial throttle it will think wide open.

I know it should set a code, but the neat thing about to sensors is that they can fail " in range" and not set a code.

Now that that is covered engine coolant temp sensors can also cause all that and fail "in range" so again no code and the ect is separate from the temp sending unit that serves your cluster...

Best of luck, I hope you get her sorted out.
I replaced an exhaust gasket (because i installed PPE header) on my 2zz and the new gasket did not cover the egr ports that resulted in a massive leak but i never had the driveability issues you describe.
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Old 05-19-2019, 05:03 AM   #8
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Strange it only report missfires. Under 3 k rpm its lean, after 3krpm its richs. What happend at 3 k rpm. Switch from closed loop tot openloop. Well in closed loop the ecu try to hold 14.7 with ltft and stft. It could be that the ltft is high due the lean condition. Then in openloop it holds the ltft value so it ads more fuel (stft is 0 in openloop ). But there must be an other cause to. The ecu should report a code for the lean condition.
So the comment from Dwebb make sense
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