any idea what readings i should be getting from this?
how to check it is working.
i know that the thread is ****ed and i can't remove it.
it just spins and spins and spins
i think the plastic outer on the sensor has seperated from the inner part.
seems a common issue as the one on my parts car is just putty glued in place....

 

You'd probably be best served by just buying a new (used) intake elbow and a sensor! I don't think that this air temp sensor would affect fueling that much though. I'll see what I can dig up on it. The OBD2 reader should be able to tell you what temperature it's seeing and reporting back to the ECU?

The coolant temperature is a sensor that would affect cold engine fueling ratios. Make sure that the coolant temp being reported isn't being reported as hot all the time. The OBD2 should tell you that as well. That would make sense. If the sensor is stuck at reporting the coolant at 200F all the time, it would mess up the fueling and gradually go away as the coolant did indeed approach 200F. Pulling the reading from the OBD2 at startup should instantly reveal that?

 

It's essentially a thermistor. I'd connect a multimeter across it and measure the resistance while blowing hot air and cold air across it and make sure it responds.

There is conflicting info in 2 Jag manuals I checked on what the readings should be.

Electrical Guide document says voltage increase with temp (so resistance going down)



Electrical Diagnostics document says voltage decrease with temperature (so resistance going up)

(Not sure how Air Temp would get to 95C!)


So take your pick!

 

The coolant temp sensor will read in the range of 1800 ohms at cold with a 9 volt battery powered hand meter , the sensor is a solid state device that has to have enough juice to function

There is a chart in the 801s doc with the CTS section

At closed loop tripping point to be " in closed loop " the value is around 280 ohms ( 88 C ) or lower

Let me verify what I said and meter leads polarity as that was not so defined in the wiring guide ( kind of squirely)

Your device should show coolant temp and closed loop mode as a closed label

 

Page 78

801S TITLE (jagrepair.com)

 

according to the fuel injector pdf that was linked above for me, closed loop mode is until 70c.

i only have elm connected to torque app and i am not sure if it has something to show closed loop or not.

but.
i don’t believe there is any issue there as the car runs very rich cold, but once warm runs beautifully.
if there was an issue there surely it would either run lean when cold, then good when warm or run rich when cold and continue to run rich when warm.
before my car was always running rich as it was not warming up.
after swapping the thermostat it warms up and runs perfect when warm

 

To change the ELM - 327 to the Parameter IDs for closed loop is not the easiest thing to do and is a learning curve to get there , but temp should be easier to get to on your app , weither the ECU does switch is another matter of the ECU hardware

it starts as default readings page and I do not have the Torque app or device as my experience is a different app / device to laptop

Question on the 70 C or 88 C as referenced in the Jaguar 801s doc somewhere

But we are looking at issues before it reaches warm or closed loop as it does fine when warm

 

definately the temp being reported is atleast close to accurate.
on the drive this morning i saw it climb.
when i first checked it was around 40c then i saw it above 80c

 

Vee has correctly commented that the “air temp. sensor” would have little effect on fueling.

Referencing the attachment, “Fuel injection primary and secondary control” there is actually no input to the ECM from the sensor, the coolant temperature sensor is the important one.

Referencing the attachment, “Ignition primary and secondary control” the air temp sensor does have an input to the ECM and would appear to apply if in either open or closed loop.



Spudmat, a common mix up with your open/closed loop.

Open Loop – The car starts initially in open loop and remains so until the 02 sensors have reached the required temp. and the engine is at operating temperature.

When conducting an 02 orientation with IDS (Legacy) on my XJR the test would not begin until the engine was up to at least 85/88c from memory.

There is no reference to the 02 sensors in open loop.



Closed Loop – Reference to the 02 sensors to allow fine tuning of the air/fuel ratio.

Most cars are set up to run on closed loop at partial throttle to achieve best fuel economy. They will revert to open loop ( our Jag does ) on full throttle as described

under the heading “Full load enrichment” in my original attachment.

There is no reference to any other sensors when in closed loop, only the 02 sensors.



I have also attached specifications for the Coolant temp sensor and air temp sensor.

Coolant temp sensors are readily available to suit the X300, here in Australia, a Tridon TCS128 is specified.



John Herbert

1996 XJR

 

Inlet air temp sensor is easily missed on cleaning the TB as the guck envelopes the sensor biasing the signal , you are adding energy to the sensor to run it , and it is not dissipating by air flow ( equilibrium ) to be at the true air itself flow temp

The effect should not accure or be in effect until closed loop in my opinion and is very negligible as Vee mentioned

You gotta hit that 88 c to be in closed loop but your issue is before that as open loop regulation

 

i have no way to determine for sure that is is going into closed loop, except for the fact that once the car is warmed the idles speed does slightly drop (indicating closed loop) and the fact that the car runs perfectly once warm.
most importantly given the fact that i previously had thermostat issues and the thermostat was stuck open and it was clearly never entering closed loop and was running rich and stalling all the time.
after replacing the thermostat the car has no issue at all once warm.
so i can only assume that it is infact entering closed loop.
i do not have a standalone scanner. only have the bluetooth elm and torque app. i have not seen the temp reading 88c but reading it is reaching over 80c.

yes i could buy and try a new coolant temp sensor or even try the one i have here in my parts car,
but i am confident that will not show anything as
A - i do not believe it to be faulty
B - i did replace the temp sensor in middle 22 (less than 15000km ago) (purchased from jag daim for the aussies here)
C - the issues i am having are when the car is cold. arising from start up. ie when the car is (supposedly) running in open loop.

the 02 sensors were replaced only 1 month later than that, and i did notice the car running more lean after that. so i do not believe them to be at fault and indicating that atleast back then the car was certainly switching to closed loop as it was evident the 02 sensors were being used in fueling.

i have just purchased an inlet air temp sensor anyway cus well why not. cheap enough to swap anyway
i did look at the readings whilst i was driving home today and it was reading 31c at the time i started checking and rose to reading ~40c. so i believe it to be accurate.



what are the factors influencing AFR in open loop?
what is the AFR which the car should be trying to obtain for ideal running?


at this point the only thing i can think is ECU.
but that also doesn't make sense as i had some issues with this stalling and then car not starting a while back. one thing i did was swap out the ECU.
and that seemed to work.
i got the TPS calibration done and it was running fine.
i put my ECU in the car that i took this one from and it ran like ****.
so i don't believe it to be ECU.
UNLESS my car is somehow at fault and breaking the ECUs.
i know i have had some issues with voltage drop but i don't believe voltage drop would cause permanent damage to electronics.
and also the voltage has never dropped below 12.5v.
i have changed my alt belt and it is much more stable. sometimes does drop to around 13v at idle. but generally sitting at 13.8 to 14.2v
but i do think i need to swap out the alternator but i have not got around to that job.

 

I could swap the ecu back and see what happens.
pretty sure i did that at one point and when putting the old ECU back in the car struggled to hold idle. and kept stalling out and was very difficult to start.

i don't believe it to be the IACV as idle speed is good
when i start the car idle speed firstly climbs up to over 1000rpm, maybe around 1200 stays there briefly and ten drops down to 800-900 where it stays.
then as the car is warm idle speed is slightly lower. when idling in gear my gauge reads just over 600rpm and the torque app shows it at around 580-590rpm.

also to note, as yet i have not tested the resistance of the temp sensor (will do on the weekend, however torque app does make it look like it is working correct), however if i disconnect it whilst the car is running the idle speed jumps right up very very high.
and then i need to shut it off after plugging it back in. so it seems to me the it certainly is giving a reading that is having effect on the running.

 

First of all, to reach open loop, you need to get to about 70C, not 88C. 88C is when the thermostat opens up.

Because something is working once it gets warmed up, doesn’t mean it’s working well.

The ECU is the biggest player in fueling when engine is cold. It stores the fueling charts the car uses to run while waiting to enter open loop where it uses sensors for fueling. So just because the other ECU ran like crap, and this one is better, doesn’t make it a good part.

The MAF, the CTS and the Coolant Temp Sensor also play pivotal roles in closed loop. So those sensors are always under the microscope first. Again, just because the car runs well warm, doesn’t mean one of these sensors isn’t bad.

After that there are secondary sensors that could cause these problems. I had not thought of the IACV, but that’s a good one. I would imagine you would be getting a code if the air pump had died, but that thing only runs for like 20 seconds, so I’m not sure it could be at fault.

By the way, idle at warm is 720rpm. In gear it’s 580rpm.

Its important to take advantage of the OBD tool because it will show you what the ECU sees, which will eliminate any chance that you are not conducting your multimeter tests correctly.

Could the EGR be faulty? Maybe stuck open? Once the car gets hot, it wouldn’t mind being open? There’s got to be another sensor that gets read by the ECU, or used by the engine before going open.

In my app, OBD Fusion, I can tell if the car is open or closed loop by looking at the Fuel System Status. 1 means it’s closed. 2 means it’s open. Maybe there is a PID in Torque that reads open/closed but calls it something else?

Maybe there’s a problem with the throttle body. Perhaps the butterfly is out of spec? (0.002” closed”). I don’t see how the TPS could be at fault? Is it at about 12.9% closed?

 

The inlet air temp and coolant temp sensor read exactly the same with a meter reference page 78 and 86 of the Jaguar 801s doc

I wondered in the past if swappable

at cold engine / air around 30 C you should see around 1800 ohms

ECU connector check by pulling back the rubber seal boots as the wires exit and if the sockets have 2 pinching tabs

You would target specific wires ...........................

Inlet temp sensor wires Red 1 and Red 9 ( there is a splice and extra connectors involved for Red 9 in the loom involving the fuel tank pressure sensor )

coolant temp sensor wires Red 14 and Red 31




Copying the 801s text and Vee's 70 C :

Cranking and after-start enrichment /

The ECM provides fuel metering enrichment for cranking and after-start conditions by increasing the injector pulse duration. Engine cranking is determined by an engine speed between 0 and 400 rpm. The injector pulse duration, and the rate at which the enrichment is decreased back to the warmup phase, are dependent upon engine coolant temperature measured by the engine coolant temperature sensor.

Warm-up /

The programmed warm-up enrichment provides extra fuel during engine warm-up based on the engine temperature measured by the coolant temperature sensor. The warm-up phase is applied when the coolant temperature is between 40˚F and 160˚F (5˚C and 70˚C)

Have you checked the fuel pressure as it may be too high as target 43 PSI at idle and 46 PSI on throttle up by way of the vacuum line modulation , there was a perfect fitting avail in Australia a couple years back on my older broke computer

Once you do reach the coolant 70 C the " fixed " enrichment pulse width is over and at 88 C tripping point into closed loop only then is the O2 sensors used for your final exhaust product ( feed back / closed loop ) to tune your pulse width for 0 % fuel trim

Question : before the regulation gets into closed loop is the pulse width only directly related to TPS and MAF to account for load ( stall ) need ( longer pulse width )

 

If you don't have a open/closed loop parameter in your OBD app, the other sure way to know is look at STFT.

In Open loop STFT will be 0. In closed loop STFT will be non zero (ideally small value).

 

Excellent deduction of " in " closed loop information , but from reading others I would say look for a shift in STFT to + or - 3 % is the best it can do target 0 % limited by the pulse width ( time ) increment's say 1/10 of a second vs. more ideally 1/100 of a second

But look for a shift toward 0 % , this can be clouded by a vacuum or exhaust manifold leak biasing the O2 sensors readings which dissipates on higher RPMs and not warm/ cold coolant ( still hot exhaust manifold sealing crack or expanding a crack ? )

 

@Vee i totally understand everything you are saying and i am not ruling anything out.

i can only say what i see and what i have replaced.

as said tho the coolant temp sensor is giving me what appears to be accurate readings in torque.
yes the ecu could be faulty but its also not something i can just swap out and test
i can only go off what i feel to be more or less likely.

i just feel for most things i am in a situation of “i have changed that” and/or “that appears to work.

getting very frustrated trying to solve this.
esp given sometimes it appears to be quite bad and stall a few times after start up.
other times it is like there is no issue.

and yep rpm range is pretty much right on point where it should be.

in AU market there is no EGR

 

So i downloaded obd fusion.
how i see loop mode?

also for only 2 o2 sensors in AU model which are the two numbers to watch?
abd for stft what exactly do you mean by “a small number?”
there might be something off there but that would not explain rich running in open loop mode even if there was

 

Vee you quote - "First of all, to reach open loop, you need to get to about 70c, not 88c." "Waiting to enter open loop where it uses sensors for fueling"
Surely you mean closed loop, this will only further confuse the issue.
Attached article sets the matter out very clearly. I believe many of the newer cars do enter closed loop very early after cold startups in the interest of better fuel economy/emissions etc.

John Herbert
1996 XJR

 

You would probably have to tell it Titania based O2 sensors if it does not automatically default from the more common X type

Lamba target 1 ( ? )

STFT in cold mode ( fuel enrichment phase before 70 C coolant point ) other than 0 , STFT in closed mode closer to 0

This chart is clear as mud to follow

Rich ( exhaust spits on garage door ) is negative STFT and the device's scale limit is -25.4 % from what I have seen on mine and reading others

I hit that - 25.4 with a missing vacuum hose from previous owner, Thanks Vee