XJ XJ6 / XJR6 ( X300 ) 1995-1997

1996 AJ16 4.0 closed loop issues (XJS)

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  #41  
Old 09-01-2024, 01:19 PM
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Originally Posted by Parker 7
Your TPS was in reasonable range of X % against others ( this is a clue the issue may be outside a TPS orientation ) and may have to return it there to shorten orientation time at shop

The TPS can be adjusted with the throttle body still installed but takes some hand dexterity and patients

The specific ( on paper ) return signal on the TPS connector as it is still installed and at mechanical idle stop is 0.60 + or - 0.02 volts DC on the middle connector wire ( Green / Yellow color ) as it goes over the fuel rail ( nick insulation ) . you can do this with engine not running , key in.

There is a mechanical idle stop screw adjustment inside the throttle body and I failed to see it on mine , someone has the details on its proper adjustment and you would have to ask yourself if it was ever tampered with to open that can of worms ( to be squared before TPS orientation )
1. Being in reasonable range simply means that the TPS appears to be working. Being close means your car will idle incorrectly. It’s either sending the voltage the ECU is expecting, or it’s gonna idle poorly. One tenth of a percentage point off is enough to mess up the idle…and emissions.

2. There was a thread a few months ago where I talked someone through with the manual adjustment. It didn’t work. Only the TPS reset corrected the problem. Search my posts if you want to read up through that. I had read that it was possible in the past, but this was the first time I had direct experience trying to make it work. It did not. You need to find a device that can do it.

eBay has cloned mongoose cables which should work at least a couple of times, but you’ll need a laptop and some VMware to download to make it work. Might even require WindowsNT with service pack 2 only. I forget.

theres also VCM1, WDS, PDU….there could be some high end shop computers that can do it too, but we’re talking 4 digit prices.

Id strongly suggest finding at least a clone Mongoose. Buy from someone who will, at the very least, support the initial install. Use it only when you need to, and it might last!

3. 0.60v is what the ECU expected to see from the factory. Over time and miles, that number changes. The ECU adapts over time with it. So no one really ever knows what that number should be set at. It could be 0.61v, it could be 0.64v.

If you swap out a TPS, you can take a reading of the old one, before removal, so when you install the new one, you could match the voltage.

If you’re swapping out the ECU; there’s no telling what the voltage it was seeing was before you installed it, so you’re working in the blind.
 

Last edited by Vee; 09-01-2024 at 01:22 PM.
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  #42  
Old 09-01-2024, 03:04 PM
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Vee ,

I think you had someone about 12 - 18 months ago that they read way out of factory paperwork ( 0.52 volts or something ) and without orientation his idle was recovered so just let be the present orientation

But in this threads present case the TPS adjustment was changed to the 7 % range so an orientation would be prudent to get it back and on " null "
 

Last edited by Parker 7; 09-01-2024 at 03:10 PM.
  #43  
Old 09-02-2024, 09:04 AM
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No, it was just the other month, maybe June. It wasn’t that long ago at all….it may have been in the x300 forums though.
 
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  #44  
Old 09-06-2024, 04:53 AM
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Update:

The car went to a garage to have the exhaust emissions checked yesterday. They report that all is good now, all readings as they should be, and it won't have any issues passing the UK MOT test next time around.

Still haven't found anyone around with the right system to perform a TPS reset, but the workaround I used has solved it for now anyway!
 
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  #45  
Old 09-07-2024, 09:47 AM
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What was the workaround?
 
  #46  
Old 09-07-2024, 12:06 PM
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Originally Posted by Vee
What was the workaround?
Elongating the mounting holes of the TPS to get a lower % reading at rest as mentioned in post 34.
 
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  #47  
Old 09-07-2024, 01:38 PM
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Glad to hear that it worked...ideally the TPS should be at 12.9% when idle, but please stick to what works.
 
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