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Here is an update on my car. I had a Jaguar classic car restorer change the throttle body with one I had reconditioned and a new throttle position sensor and idle air control valve were also fitted. They are very much centred on restoring e-Types and the odd XJS. An X300 is viewed as modern. They do not have the software to reset / reconfigure the TPS (but may get those tools soon as these cars become "classics") so currently I have not had the throttle adaptation done...
The car is definitely better than before, it is more responsive and has no flat spots. It does idle slightly too high and drives itself a bit when cruising so I need to find somewhere to do the adaptation on the TPS.
I am currently experiencing another issue, which was intermittently present before this work and I believe it happens when the weather is hotter (it is just below 30 degrees C here) and more when there is no wind. The car struggles to start and will idle lumpy for a few seconds and stall. Starting it multiple times and revving it will get it going and after a short while it will idle fine and then drive perfectly.
This evening I put my OBDII adaptor on the car, basically the car runs badly until it goes into closed loop mode, when it does it idles well. Does anyone have any idea why this might be?
Also I have noticed that the car is now idling and driving better on LPG than petrol, I am considering changing the (petrol) fuel pressure regulator and fuel filter as Katar83 has done.
In the open loop mode after startup the fuel mixture is purposely rich until it goes into closed mode so that would point to a mixture too rich until leaned . The ECT and to a lesser extent the IAT sensors effect this , the first item shift the open to closed mode for the ECU and the IAT effects the mixture to lesser extant . The 2 sensors are the same and they should read the same before warming up the engine . You can see this with your device or can read resistance with a meter of 1500 ohms off the top of my head .
The O2 sensors have a role in this as they are not used in the open mode until closed . The sensors can be off properly reading and when used in the closed mode can favorably bias a problem elsewhere by bringing the mixture down .
Given the number of specialists who have already been over the ground, I feel sure this will have been covered, but have you inspected the exhaust around the manifolds and downpipe area? The reason I ask is, as I found out the hard way, leaks in this area can cause air to be sucked IN to the exhaust syatem ( very counterintuitively in my view!) which in turn the lambda sensors interpret as a weak mixture, and then enrich it, leading to weird stft readings and poor fuel consumption in my case.
At this point anything is possible. I have been chasing this issue for nearly two years
I do not think this has been looked at in any detail, there could be a hairline crack I suppose. At the weekend I plan to look at the readings from the ECT and IAT sensor and study the STFT using my ODBII scanner, but beyond that I think it is back to a competent specialist to look at the exhaust manifolds and set the TPS adaptations.
Any mechanic with jaguar software can reset the TPS. It’s actually not that rare, especially if they also work on land rovers. Look for an export car expert, or even the dealer. It takes only a few minutes. That’s the easy one to reset.
Base idle adaptation reset requires a PDU, so forget that. The TPS reset will settle your idle back down, assuming there’s no vacuum leak.
Thanks Vee, given where I live and the lack of Jaguar specialists locally I am going to take the plunge - the car is booked in to Jaguar in Canterbury next Friday to have the TPS adaptations set. I will look at any remaining issues from there.
This evening I put my OBDII adaptor on the car, basically the car runs badly until it goes into closed loop mode, when it does it idles well. Does anyone have any idea why this might be?
Until it goes closed loop that means the car is running on tables in the ECU. The biggest influence on where the tables are referenced is the coolant temperature, so I would start by changing that sensor. . Others are mass air flow, and air temperature is a trim factor that isn't too significant. Your mass air meter might be suspect.
When it goes open loop what do the short term fuel trims do? Do they move considerably from the open loop values? If so, that would suggest that the O2 sensor are correcting a basic fuelling error based on the exhaust. Another possibility is the fuel pressure regulator and it's holding the fuel pressure either too high or low.
Thanks to everyone for putting up with my never ending forum thread. Next Friday the car is booked in to Jaguar to get its TPS adaptations set, so the ODBII readings I refer to here are based on the car idling too high.
So this evening I connected my ODBII scanner and looked at the engine coolant temperature sensor readings and intake air temperature sensor readings before I started the car; the coolant temperature sensor was showing 156 degrees C (!?!) and the intake was 24 degrees C (which was true). After starting the coolant temperature fell to closer to atmosphere temperature and then rose to 90 degrees C, is this the normal behaviour?
Today I had no start and stall / start and rough idle issues. The car quickly went into closed loop mode and I then captured the following readings, idle was reasonably OK, but sitting in the car you could feel the odd idle fluctuation but nothing that bad. (As always car seemed to idle slightly smoother on LPG than petrol).
Please note the needles obviously shows the reading at the time I took the screenshot, but the red and orange markers show the high and low readings since I started the car, does this look normal to you guys?
Please note I have new IAT and ECT sensors.
07-16-2018, 04:12 PM
