I need help re-setting the computer in my 1995/1996 XJS (The forgotten years)


The CEL is on
I can't read the code right now, but I was getting
P0300 random misfires
bank 1 persistent misfires (don't remember the #'s)
bank 2 persistent misfires
bank 2 sensor 2 high voltage


I'm getting 11-12 MPG


The Autel showed me the down stream O2 sensors looked reversed, so I switched them. Light stayed off for a week, but no other improvement.


I need to re-set my TPS and fuel trims, and see what exactly is wrong with my engine control that keeps the idle at 2000 RPM.


There is NO IDLE SCREW, TB is set correctly and is clean, there are NO vacuum leaks.


Inspection / Test tools I have purchased:
A Mongoose cable
Version 131 of the JLR software VDF+SPA Calibration
Version 181.5 IDS of JLR software
a (cheap china junk) VCM with version 141 JLR software

a laptop, and done a clean install of XP PRO

Autel Maxidiag Elite MD802 , and returned it when it did not work as advertised


I still can't seem to connect and write to the computer.


The mongoose doesn't see the VCM (its not in the circuit, so no wonder, but why is it looking?)

The VCM wants to go online to update, but some posts I have read said not to go online or it will update to a new licensing requirement. Absent going online, it ticks out.

Background
I purchased a 1996 my XJS 11 months ago, 85K miles, and have not been able to reset the idle from about 2000 rpm. I have become so desperate, I took it to the San Jose Dealer. He blew through $800, repeating much of what I had done, and said "The computer must be repaired for $2800".
I took the car back, sent the computer to someone on EBAY who could not find any computer fault.


I have
cleaned the throttle body
repaired the "PVC" system (big leaks before repair)
checked the valves, powder-coated the disintegrating mag valve cover, new rubber
replaced the spark plugs with Champion old ones clean but worn
Replaced all 6 of the coils
replaced the fuel filter and pump (and sender...at least that works now )
replaced the disintegrating radiator, all belts and hoses (I was there anyway)
Burned up my brakes driving it (got to get to work to support this habit)


Beaten down, but not willing to quit.


Ready to buy and test the next possibility; I must get this thing smogged and registered.


Any and all help gratefully accepted.

 

The Mongoose will allow you to do the following:
1. Reset oxygen sensor orientation (which it appears you have already resolved) and
2. Reset TPS parameters. That can be done manually.

That's it. The most valuable tool...resetting the fuel trim parameters is NOT something you'll be able to do.

It sounds like you have done most of the items that needs checking, but you have not specified whether the TPS was adjusted. As I mentioned before, it can be done manually. You have to loosen the screws that hold it to the throttle body (from below) and backprobe two of the three wires. You'll have to check these forums, but I believe the low range was something like 0.6vdc and then as you actuate the throttle manually, the numbers should sweep. Any drops and it needs to be replaced.

I forget which two wires need to be back probed, but you'll know it when you get the right range read...you basically have a 50/50 shot.

 

Unfortunately, the TPS is not manaully adjustable, only the computer can adjust it. It is mounted with 2 screws with straight holes.

 

It isn't supposed to be adjustable, but it is, it only takes a little bit of twisting to get the readings to move. If you can't get it to 0.6v, then I would recommend removing it, and expanding the holes, or slot them slightly.


It doesn't take much. There's a little play.


If you can confirm what the reading at idle is, you may not have to do anything and we can move on.

 

Another recommendation: Try contacting Carlsbad British Motorcars. They may have the PDU that will most likely fix your problem.

 

Is it the real Mongoose from Drew Technologies? I.e. the ~$600 one? it should connect to the car with that plugged into your laptop and the V131. You won't need the VCM.

Typically, you have to go through letting it read the VIN automatically and fail, then enter the VIN manually and then you will have access. I've only done it on an X300, not XJS, but should be similar. The idle adaptation is what you need to do, as the ECU is not seeing the throttle position as closed so won't adjust the idle air motor.

Just out of curiosity, have you verified that the throttle is actually closing all the way? Turn it by hand and see what happens. The throttles on the 4.0's are well known for sticking and not closing properly. Pull off the rubber bellows and see how much gunge is in there.

I picked up a 95 VDP cheap because it was driven on short trips and the throttle shaft became gummed up. When it stuck open the lady driver panicked when the car wouldn't slow down she ended up in the ditch. Car was repaired, but they didn't cure the high idle, so she sold it. I replaced the throttle body and had a very nice car after that.

 

I am not aware of any product that can be purchased which allows us to Reset Idle Adaptations. The PDU does that, but is unavailable.

I have a Mongoose knockoff running, I believe, IDS v131.5 and it is not something that can be done.

I have searched for something that can do it, even reaching out to the people who make the AutoEnginuity software, but failed everywhere.

If anyone knows about some piece of hardware/software that (is available and) can do it, please let me know.

The OP mentioned that he has cleaned up his throttle body. Assuming he found all vacuum leaks, I would suspect the TPS may not be adjusted properly. Short of that, he'll need a shop with a PDU.

 

Thanks for the suggestion. I well check as soon as possible and post. I may end up going to Carlsbad, but it is a 7 hour trip

 

stomper I sent you a message bout all this. did you get it.?

 

I should have included the crank sensor in the list of replacement parts, and amsoil fuel system cleaner for the injectors, a new fuel regulator, and a used mas.

On the freeway, after brake fade was setting in, I put the car in neutral at about 30 mph, and the engine is settling at 3500rpm. This does not seem like just an idle problem.
No chance to work on it this week. ..

 

The throttles are known for gumming up and not closing under the return spring pressure. Can you turn it by hand and watch the throttle plate to make sure that it is returning to fully closed?

Or with the car in neutral blip the throttle fast and aggressively and sometimes that will snap it closed.

 

Other than taking it to the shop, as I recommended before, it is plausible that your problem lies with:


1. Coolant Temp Sensor - You should be able to read what the coolant temp sensor is sending if you have an OBD2 reader. (I use Yhasi Movi because it works with my MacBook, but there are plenty out there, including those that work with your cell phone) The sender and the sensor are two different parts, so the gauge on your dashboard could be working properly but still be sending a bad signal to your ECU.


2. Idle Air Control Valve - Read this thread. https://www.jaguarforums.com/forum/x...-150942/page2/
It includes the instructions on how to do a manual reset on the IACV. There's a ton of useful info in the thread.


I still say it needs to be hooked up to a Jag Specific computer to reset throttle adaptations, however please keep us posted.

 

I found a local mechanic with a PDU, and he fixed the idle. The story is, this guy went to Puntnam Jaguar in Redwood city right after he was discharged after his service in Vietnam, and he has been there ever since. Putnam is no longer a Jaguar dealer, but this guy still has a car from that era, and his own PDU. The downside is the same problem I have with every capable person I find, he will retire at some point, but for now he is able and willing.




I really have a problem with not being able to fix my own car...not sure I will keep it.


For what it is worth, I replaced everything that everyone suggested, on my own, BEFORE I paid a dealer to work on my car. My view is I get NOTHING when I buy labor; if I trouble shoot with parts at least I get the parts...


1996 JXS, light green metallic, Clean 92,xxx miles, runs well (for now
Scott

 

Stromkee,
At least your issue is fixed!
Can you tell us how that specific PDU was able to fix an issue that could not be addressed with a Mongoose/IDS-SDD unit?
And does it mean that we are stuck if such PDU cannot be sourced?

 

Do a search on this forum for "Reset Adaptive Terms". This is what only the PDU can do.

 

I bought a Mongoose cable and version 118 software. I also bought an IDS clone (cheap china junk). I bought a copy of Windows XP PRO, and wiped an old laptop so I could run it...I could see the things I needed to change, but they were grayed out...no access.


Now I can't seem to press on the front stub axle grease seals...maybe I am loosing my touch...getting grayed out...

 

What did you run/see? I happen to have the same mongoose knock off. It runs okay, more importantly, it does the job at a fraction of the price.

You could have bought the non-Chinese product you know.

I have been able to reset the TPS as well as reorient the oxygen sensors. What is it that is greyed out on your system? My version lets me select everything, but most options are "not supported by my car".

I'm always interested in hearing more about other people's experience using the IDS/WDS. One day I'd love to find something that can replicate the PDU.

 

By the way, from an earlier post I made about the grease seals:

6. Installing the grease seal is easy if you use a flat block, or board. Using a hammer to tap it in is completely useless. I couldn't get it to work. By starting the seal in on one side of the circle and then laying a flat piece of scrap wood and pressing down on it got it in in no time.