Bang my head: call to all experts, Corolla

[Xulfiqar]

That trim pot does not act like an o2 sensor replacement but more of an AFR sensor replacement but only for idle mixture. Its a pretty simple device to work out, but for 90% correction (100% is not possible as its a fixed unit) you need an EG analyser to work with it, make sure when you use such EG analyser your engine oil is not a cheap variety as it can upset the EG content - specially when checking an EFI engine EG.

Imagine it as a base setting and off idle response setting.

[Xulfiqar]

dont try to measure it with a multimeter on V, its useless - the only way to see it working is to test on resistance scale.

[SER_GTR]

we are talking about VAF sensor which in sadi english pashtoo you guy's called varistor/ resistor for afr adjustments.(A)

so I know that haji saab you are(H).............

Hajii Sahab

Its Called Variable resistor..Its Not Any Kind Of sensor......Usually Called Trim POT

VAF Sensor Is Something Else....Don't Know About Ur Desi Pashtoo terms.....!!

[SER_GTR]

Thanking you so much atta for showing me a way, I tested the variable resistor in a time I had. I was able to verify the VC (Power Wire), E2 (Ground) and VAF (Signal wire). Link to the document below on EFI variable resistor was also a great help. Somehow VAF (signal wire) was not showing any voltage once I took the measurement with respect to battery?s ground as document says that Voltage is suppose to vary between 0-5Volts. While car was idling, I removed the sensor expecting a response but nothing happened, not even a engine check light like it does not matter if sensor is there or not. Again, I tried to measure the Voltage between VAF and battery?s positive and this time it turned out to be 13.30 Volts against 14.20V between battery?s terminal. Then being curious, I started to turn the variable resistor towards R and did not notice even a slight change in Voltage either with respect to battery?s positive and still showed zero w.r.t battery?s negative. Document describes values for correct resistances but here it seemed completely out of aspects and in hundreds.

I think, I will need to buy this sensor from scrap yard, maybe problem is that this part is not working at all and further need to test everything again and verify my observations.
http://www.moranbahweather.com/toyota/lc_trj12/rm/rm1151e/m_05_0187.pdf

Simply Disconnect The Sensor Reset ECU And Check....!!

CEL Might Appear But Problem Should Resolve If Its The Culprit...

B.t.w Measure The Resistance In OHM's Between terminals.....1-2 And In Kilo Ohms Between 2-3

[talhawaleed]

not maybe sure 50000% sure your car run's lean at cold start. and clear one thing up the varient's of toyota vehicle's with Vane Sensor type does not show any fuel trimming at all clear this concept before now come toward what is happening in your vehicle right now. vane sensor has to be adjusted according to each tuneup you done at different milage's so in your case it is still at stock setting so first tell me the actual milage on your odometre so I can calculate the total tuneup volt's for the VAF.

Thanking you so much atta brother, finally I have been able to resolve the issue. It?s surprising, that I highlighted this to many people including the lead mechanic at many Toyata motors but they flatly refused that problem be with variable resistor even-though I told him that?s the only thing which is left and being suspected but he insisted on working on parts which already been verified. I have searched everywhere, but found no answers, help or clue. I wonder, how many mechanics must have ripped the poor owners on same vehicle as I find none who even had a clue to this and I already spent a lot on same things over and over again.

I was able to remove the variable resistor, find 5 volts adopter for powering the sensor, first measured the resistances which turned out to as follow while comparing it with document, I suspected the problem until I connected it with 5volts adopter.
http://www.moranbahweather.com/toyota/lc_trj12/rm/rm1151e/m_05_0187.pdf

VC to E2: 4.52k Ohms as compared to range of 3.5 to 6.5 Ohms as prescribed in manual
E2 to VAF: 1.02 k Ohm as compared to range of 0 Ohm to 5kOhm
VC to VAF: 3.6 k Ohm, range not prescribed

But once, I connected it with 5 Volts adopter then voltage varied from 0 to 4.55 Volts so knew that the part to be good. Voltage decreases once moved towards R and increased once moved towards L. Found the initial value on resistor to be 0.8 Volts but adjusted to 2 Volts and modified the wirings for testing on car and once connected the problem was already gone and car was rocking. Information, you provided on phone was very helpful such as that it comes from factory with preset value at 1.23 Volts and adjustment to 5% per 50,000km so later, started decreasing the voltage till I brought it to 1.3 Volts as found the RPM to be more stable on this and near to that with CNG. Took the car on drive, able to climb up on a hilly road, stop in-between and still able to move without even a slight hesitations and these were the things I never imaged doing before on petrol, now such tremendous power this car had.

I will further test the vehicle and will keep you informed regarding its status. I hope, you will enjoy the pictures I have taken while testing this, a big thanks to you and a way of hope to others facing similar issue.

[Xulfiqar]

how bad was the original setting?

[talhawaleed]

dont try to measure it with a multimeter on V, its useless - the only way to see it working is to test on resistance scale.

Sorry, I just read your message, resistance on this variable resistor was completely out of specs as compared to given on document found on net. Maximum voltage it read was 4.55 Volts while minimum was 0. There were two labels on resistors “R”, “L”, I guess R points towards Rich and L towards Lean. But once screw was turned towards “R” then voltage decreased and once towards “L” it increased. I was expecting the opposite but since eventually ECU was interested in Volts it receives so does not matter what the internal mechanism be. I guess, if maximum Voltage registered was 4.55V as compared to 5Volts then internal mechanism of resistor must have deteriorated that’s why I must be experiencing this issue. I will again test this in terms of variation in resistance.

Any other way, I can tune this without having access to exhaust analyzer or any known value you think is best suited in absence of this equipment. Too much petrol is also an issue as compared to more swear in terms of lean condition.

[talhawaleed]

how bad was the original setting?

I guess, it was around 0.9 Volts, as I remember yesterday, expecting the part to be completely bad, I slightly moved the variable resistor towards R. Today, once I checked it then it was at 0.9 Volts. Yesterday, I was trying to be careful with original wirings but today in-order to be sure before disposing the part, I had to cut the wires to detach the sensor completely along with grip. Honestly, If I had moved the variable resistor towards R yesterday then tried to move the same amount back to its original position.

[Xulfiqar]

this never goes bad unless it was flooded with water which shorts it out. Ideally you dont want the mix to be too lean to prevent valve seat problems.

[talhawaleed]

I have the very same issue with my 4AFE. Never bothered to get it sorted out as all the mechanics would make a meal of it. As far as I think, it has all to do with the ECU programming. I reckon there are saved settings for engine start up i.e amount of fuel to be injected at the specific temperature. Since the engine temperature is low at cold start up, the configured settings either inject excessive fuel or less fuel. Good luck

RESISTOR, VARIABLE
89456-30010
AE112..GCC,GEN,IDN,VEN
AE111..(GLI,XLI)..(GCC,GEN,GENKD,PHL,VEN)

Is applicable in all these engines, if your car has and you have cross checked tappet settings, injectors, ignition coils, connectivity between coils and engine, connectivity between injectors and engine, fuel pressures to be ok,, inlet temperature sensor and coolant temperature be fine then go for this simple DIY.

[talhawaleed]

this never goes bad unless it was flooded with water which shorts it out. Ideally you dont want the mix to be too lean to prevent valve seat problems.

I don't remember that I ever touched this unit before. unfortunate I guess but I had been avoiding petrol as plugs would go dirty very soon that’s why been trying to drive it on cng mostly . I hope, driving on CNG must have avoided valve seals from going bad, can’t say further but hope they be good. I was recently scared as hell, as now my dad drives this car, CNG about to shutdown and nothing I do would fix the issue and feared how would I rescue him if car went bad as he is old now.

[talhawaleed]

its called CO tester....and suzuki township has two units

that maybe in Lahore, if its in Rawalpindi/Islamabad then i will pay one visit for fine last adjustment.

[talhawaleed]

m having the exact same problem with my Gli 07 which is 115000 on ODO n it also stalls if i accelerate it on cold start-up... but after starting my car n idling just for a minute it becomes perfectly fine n then no stall at all !!
i showed my car to many gud mechanics but no solution at all... everyone told me its normal in winter season ur car is perfectly fine (A)
so do update us if u find any cure to this problem !!
P.S : my car is running on petrol from December 2012 no CNG after that !!

i guess, we got a cure now.

[SER_GTR]

this never goes bad unless it was flooded with water which shorts it out. Ideally you dont want the mix to be too lean to prevent valve seat problems.

This Is Actually The Last Thing People Think Can Go Wrong....!!

And Flooding It With Water Is Easy JOB.....Just Service It Once And You Are Good To GO...!

[SER_GTR]

Sorry, I just read your message, resistance on this variable resistor was completely out of specs as compared to given on document found on net. Maximum voltage it read was 4.55 Volts while minimum was 0. There were two labels on resistors “R”, “L”, I guess R points towards Rich and L towards Lean. But once screw was turned towards “R” then voltage decreased and once towards “L” it increased. I was expecting the opposite but since eventually ECU was interested in Volts it receives so does not matter what the internal mechanism be. I guess, if maximum Voltage registered was 4.55V as compared to 5Volts then internal mechanism of resistor must have deteriorated that’s why I must be experiencing this issue. I will again test this in terms of variation in resistance.

Any other way, I can tune this without having access to exhaust analyzer or any known value you think is best suited in absence of this equipment. Too much petrol is also an issue as compared to more swear in terms of lean condition.

BEST Is To Use AFR Sensor To Know Exactly Where You Stand.....BEside These Readings So Many Things Matter Also SO AFR's Can't Be Read Until Unless You Have AFR Sensor....!

Once You Have It COnnected....You Know Exact Correction Needed To Be Done...Else Its Just Shooting BLIND In Dark...

[SmilingTulip]

Do I need to change this sensor?

[SmilingTulip]

RESISTOR, VARIABLE
89456-30010
AE112..GCC,GEN,IDN,VEN
AE111..(GLI,XLI)..(GCC,GEN,GENKD,PHL,VEN)

Is applicable in all these engines, if your car has and you have cross checked tappet settings, injectors, ignition coils, connectivity between coils and engine, connectivity between injectors and engine, fuel pressures to be ok,, inlet temperature sensor and coolant temperature be fine then go for this simple DIY.

Do I need to change this sensor?

[atta1111]

This post was flagged by the community and is temporarily hidden.

[abc01]

where is that resister located

Sorry, I just read your message, resistance on this variable resistor was completely out of specs as compared to given on document found on net. Maximum voltage it read was 4.55 Volts while minimum was 0. There were two labels on resistors ?R?, ?L?, I guess R points towards Rich and L towards Lean. But once screw was turned towards ?R? then voltage decreased and once towards ?L? it increased. I was expecting the opposite but since eventually ECU was interested in Volts it receives so does not matter what the internal mechanism be. I guess, if maximum Voltage registered was 4.55V as compared to 5Volts then internal mechanism of resistor must have deteriorated that?s why I must be experiencing this issue. I will again test this in terms of variation in resistance.

Any other way, I can tune this without having access to exhaust analyzer or any known value you think is best suited in absence of this equipment. Too much petrol is also an issue as compared to more swear in terms of lean condition.

[SmilingTulip]

what is your car's problem pm me for more detail's

Same as Talha's.