I have the 1996 XJS with the AJ16 engine.

I have been able to piece back together a fully functioning WDS. It lets me reorient oxygen sensors and reset the TPS, however when I ask it to reset the base idle adaptations, it wants me to input some CO readings, in either ppm or %.

I came across a product called "Gunson's Gastester". This device is made to measure CO readings from a tailpipe, for the home enthusiast! Reading up about it, it isn't terribly accurate, but maybe close enough?

I then thought, what if I just take the car down to my indie garage and have them run an emissions test on the car and use those readings? That would be perfect, and they should only charge me the going rate for a state inspection!

Does anybody have any other ideas or suggestions? It would be pretty amazing if I were able to pull this off with the WDS.

 

I think that will reset the idle fuelling, which is open loop, i.e. just runs off table values, without any sort of feedback from what the fuelling actually is.

Does your idle mixture need to be changed? If you do take exhaust readings, make sure they are before the catalytic converters.

 

Wait, what? Before the cat converters?

I wasn’t expecting that! I’d have to pull an oxygen sensor for that, no? The WDS is not very specific about how and where to take the reading. I assumed it would be from the tailpipe! (You know what happens when you assume)

So I have had my ECU successfully refurbished. The O2 sensors were flat before, not they’re certainly chugging along. I’m getting great mileage on highways (in the mid 20s) but I have a couple of issues:
1. High idle. 1,100rpm in Park, 800rpm in gear.
2. LTFTs are at 56.25!!!! I know that’s just a math equation result, but damn, I’ve never seen that before!

I haven’t heard back from the shop that refurbished it, but I thought I’d see if I could finally use the WDS to reset it myself.[/left]

 

The high idle can be a TPS reset, then you have established where closed throttle idle really is. However, have you cleaned the throttle body and moved it by hand to make sure it really is closed?

I had a 95 VDP that the throttle was sticking and wouldn't fully close unless I very aggressively blipped the throttle (in neutral) to let it close. I tried cleaning and replacement was the only fix.

Did you replace the O2 sensors with the right kind? And put them in the proper places? Jaguar used the Titania sensors that are different to just about every other car out there. They change resistance in response to O2 levels, rather than voltage.

If you are resetting the base idle fuelling, you would want to know a CO level before it's been modified by the cats. Otherwise a rich running engine is masked by the cats and you won't be able to measure it.

 

The TPS percent open shows correct at 12.9% when foot is off the gas, so I don't suspect the TPS reset will help, but I can try that this weekend.

The throttle body is clean. I had it off last summer and gave it a thorough cleaning. I inspected it this past weekend and it still looks great. (I added an oil catch can, so there is no more oil residue making it to the throttle plate from the intake elbow)

The O2 sensors have the correct Titania type sensors. I used Bosch brand.

The base idle is perfect under the original ECU. Only when I swapped in the refurbished ECU do I have a high idle. The ECU is obviously the culprit. I was hoping I could use my WDS to cure the problem myself. I just don't know how to take advantage of this option.

Taking a reading from before the cat is fine, as long as I know thats what it wants to see. I'd have to buy a sensor that fits into the oxygen sensor bung, right? Then how do I know which bank to take the reading from?

 

Ah Ha! That's where you need the TPS reset! As there is no mechanical adjustment in the TPS to obtain what the ECU expects to see as closed throttle voltage, it's done by the WDS. Think of each ECU and TPS as a matched set, calibrated to each other. You've changed one component, so now you need to recalibrate them to each other.

The closed throttle voltage is obviously different in the new ECU, so it's thinking you're not at closed throttle and therefore will not allow the idle air controller to work. When you recalibrate the new ECU to the TPS at close throttle it will recognize that it is now at idle and will allow the idle air controller to adjust idle speed.

Try doing a TPS reset and I bet your idle will come down, since it was fine with a different ECU.

 

TPS position when closed is paired and stored with the ECU so your 12.9% is fine with one but not the other. You either need to do the TPS adaptation or adjust the TPS position(it's possible with loosened screws to adjust it within maybe 0.01v which is always enough)

 

Good to know. I will absolutely try that this weekend then. Shouldn't take long at all.

Will report back when I'm done.

Thanks for the help.

 

SUCCESS!

I hooked up the WDS, ran the TPS adaptation and I'm idling where I should now!

I'm going to assume my LTFT will drop as I drive the car more.

Thanks for the help.

 

I'm sure the LTFT will come down as you drive, as the ECU had adapted to the other engine, and now it has to relearn how your engine runs.

 

 

Can you do the o2 sensor orientation? I thought this should reset the LTFTs, if it still get high than look at other things, temp sensors, MAF, spark plug gap, air leaks.

 

I can confirm that reorienting O2 sensors does not reset any of the trim values.

I swapped out this new refurbished ECU for the old one, and everything is back to normal. It is definitely an issue with the ECU. My car was not able to run. I started her up after driving to work and it would turn over, but then die. If I immediately put her into drive and kept the gas on, she would run, but at a stop light, she would stall out.

The bizarre thing is that my mpg is back where it should be, low 20s for highway driving...

 

Obviously the fuelling isn't correct, as the ECU learned from the previous car. That's indicated by the STFT being maxed out and the LTFT being so high. I believe it will slowly relearn and change the LTFT as you drive with the STFT constantly biased one way.

I don't know enough about WDS to know if there is a "factory reset" you can do to return it to the base setting.

 

The car is not safe to drive. It will die if it comes to a stop, it may die if I don’t maintain some kind of fuel delivery. It seemed to drive fine this morning. I parked it for a few minutes, then couldn’t get it to run without applying gas.

I bought the Gastester. I should now be able to see CO amounts in my exhaust. I’ll see what that does when I select the mysterious “Fuel Trim Setup” options in the WDS menu. No one seems to know what that does, or how to use it....

As always, I will report back. It will take me at least a week to get it and use it.

Thanks for the continued interest.

 

Is this with the first ECU or the second? It runs fine with the second, but at increased fuel consumption?

 

The primary ECU was drinking more fuel than normal.

I had saved an ECU from a previous car (same MY, both 96 XJS) that was not reading the oxygen sensors properly. The readings were not flip flopping, they just stayed flat so it prevented the car from going closed loop.

One day, I found a company that said they could refurbish it, so I figured I’d get that ECU working perfectly while continuing to use the primary as a backup. This afforded me the time to wait to get an ECU refurbished (about 6 weeks). I figured I have this spare ECU, might as well spend the time to get it working again. They did fix the oxygen sensor issue, the car definitely goes closed loop, but seems like I may have to send it back for some more work.

I ended up plugging the primary ECU back in now and my mileage went up? Who knows what’s going on.... LTFT still showing 7.8 on the primary. (Its 56 on the refurbished)

 

Last time I had a fauly o2 sensor in my old x300(same AJ16 engine), it took me 2 months of driving to get the high LTFT down to normal levels.

 

The LTFT is just a math equation using STFT. I think the issue with this refurb ECS is the fact that is sits on +24 STFT when idling in park or at a stoplight. That’s not right.

 

My hat's off to you for staying after this.

My 1995 XJR with the AJ16 never had fuel trim readings that were within range. I eventually threw-in the towel.

Cheers
DD