High Idle -96 XJS 4.0 Help!
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High Idle -96 XJS 4.0 Help!
So.. recently acquired a 96 XJS Conv with 43,400 miles. Having and issue with fast idle (cold start or warm) About 1500 rpm Seller noted that common cause was idle control or stepper valve. I replaced it today and the idle initially jumped to 2800 rpm After driving settled down to 1600 rpm. I briefly obtained a normal 700 to 800 rpm idle after removing the stepper valve, cranked the ignition which activated the stepper valve motor. Reinstalled the stepper, and reset the system by battery disconnect. But, the next time i started the car and drove, high idle has returned 1600 in park, and up to 2800 in neutral while driving. Suggestions? Seller insists it has to be stepper valve and possibly may need to re-flash the computer
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It's a well known issue with the AJ16 engine. What you need is a Throttle Adaptation, and you'll need dealer level software to do that. See this thread for an example: https://www.jaguarforums.com/forum/x...-death-179174/
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motorcarman (11-11-2017)
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#8
Agree with those above.
I'm afraid it's a settings issue and can only be correct by a "vintage" Jaguar diagnostic unit. The one I'm aware of is the Jaguar PDU unit. Although I think there are others.
The modern equipment is not compatible with these cars so not all dealers will have one.
Via one of those units it's literately a half hour job.
My dealer doesn't have one so they wanted to replace the throttle body, stepper motor, and most of the other parts at a cost of nearly £1000. Pretty unimpressed by their service, lol
So I just live with it. Car idles at 1,600 at cold and drops to around 800-1,000 once warm. I can live with that.
Annoyingly I had the issue previously and someone at the garage did "reset" it for me with no issues, but this time around, either I'm getting the wrong mechanic or someone who doesn't know anything about XJS's but it wasn't worth pursuing.
If I'm in the UK at some point in the future I'll try and book an appointment with a XJS specialist to get it sorted but take it from me, it's not mechanical. It's electronic.
I'm afraid it's a settings issue and can only be correct by a "vintage" Jaguar diagnostic unit. The one I'm aware of is the Jaguar PDU unit. Although I think there are others.
The modern equipment is not compatible with these cars so not all dealers will have one.
Via one of those units it's literately a half hour job.
My dealer doesn't have one so they wanted to replace the throttle body, stepper motor, and most of the other parts at a cost of nearly £1000. Pretty unimpressed by their service, lol
So I just live with it. Car idles at 1,600 at cold and drops to around 800-1,000 once warm. I can live with that.
Annoyingly I had the issue previously and someone at the garage did "reset" it for me with no issues, but this time around, either I'm getting the wrong mechanic or someone who doesn't know anything about XJS's but it wasn't worth pursuing.
If I'm in the UK at some point in the future I'll try and book an appointment with a XJS specialist to get it sorted but take it from me, it's not mechanical. It's electronic.
Last edited by Andrew Harper; 11-11-2017 at 06:11 PM.
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Andrew Harper (11-11-2017)
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What I would recommend is to take it to a Jag dealership, or a shop with Jag specific diagnostic software and perform a TPS reset. Should cost no more than 1 hour of labor, considering it will take them less than 15 minutes to perform.
I’m no longer confident that adjusting the TPS manually would resolve your problem.
Do you have an OBD2 reader that can see what the Throttle Opening % is at idle?
Replacing the TPS will not resolve your problem. There is a ton of information on these forums regarding high idle.
I’m no longer confident that adjusting the TPS manually would resolve your problem.
Do you have an OBD2 reader that can see what the Throttle Opening % is at idle?
Replacing the TPS will not resolve your problem. There is a ton of information on these forums regarding high idle.