I have a 95 XJS that has a Extremely High Idle , when I first start it up when it's cold it goes to aprox 1300 rpm, then after warmed up I can drive off normally and it fine til I shutoff the engine. When I restart the engine, no matter how long after I just shut it off, it will jump to aprox 1500 - 2000 rpm and will not come down. I have cleaned the throttle body, MAF and air cleaner and changed out the Idle Air Control Valve., to no avail, would appreciate any help. I also ran a diagnostics check and NOT getting any trouble codes. Desperate in Missouri...

 

Could be an air leak.

 

Welcome to the forum usaf,

I've moved your question from General Tech Help to XJS forum. This is the place to post technical questions about your model.

Please follow this link New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum to the New Member Area - Intro a MUST forum and post some info about yourself and your vehicle for all members to see. In return you'll get a proper welcome and some useful advice about posting to the forum.

Graham

 

Which model and engine do you have?

 

I have the straight 6.

 

Hi there, I would try a search with the words "idle" and "AJ16" and you will get a good idea, but basically you are looking at a bad idle control valve, bad TPS, or sometime the ECU just needs to be reprogrammed. Has the car no been driven for a long time?

 

It was sitting in a car dealership lot a long time.

 

The main thing I cannot understand about it is, when the engine is cold it starts right up and runs fine until you shutoff the engine and restart it, then it's high idle until its cold again..Ive replaced the IACV. Im not going to replace the TPS until I have too almost 500.00 and there may not be anything wrong with it. I've cleaned the throttle body, cleaned the MAF sensor and air cleaner. There is not a Jaguar dealership within more then 200 miles of this place, so thats out. I bought that a normal repair shop would have software to reset the idle or ecm on this car. Thanks for your response. I don't have a repair manual or owners manual on it either.

 

You need to find a shop that has the jaguar specific software, WDS, IDS or even PDU. A shop that has this software can reset your base idle setting.

You won't resolve it any other way.

 

Sorry, do not know what WDS, IDS or PDU is.

 

It's the computer that resets the ECU to the original parameters.

If you are saying that you have normal 550-700 idle at sometimes then your CTS might be bad. But typically these cars need to have the parameters reset like Vee said

 

Im sorry but I don't know what CTS is..i've just owned this car for a couple of weeks and learning about the hard way. No owners manual and no repair manual.

 

CTS is coolant temperature sender.
Download the Kirby Palm book as it has several tons of useful information:
http://www.jag-lovers.org/xj-s/book/XJS_help.pdf
The six cylinder units are prone to sticking throttle butterflies as they get gummed up; take the air cleaner off and clean it if it is all gunky.

 

Ive already cleaned the throttle body

 

https://www.jaguarforums.com/forum/general-tech-help-7/ids-sdd-naked-truth-32683/

Read through the above thread to educate yourself on IDS, WDS and PDU.

You need to find a shop that has jaguar specific software. There should be a shop around you that specializes in foreign cars maybe?

 

They specialize in foreign cars but not Jaguars

 

So, is the car running normally at some points? Is the idle ever normal, between 550 and 700 or so? Because that does point to a CTS.

 

550 would be low some times around 700 to 750.

 

700-750 sounds like the right idle out of gear...550 sounds right in gear.

If this is an intermittent problem, I could be wrong about the base idle reset.

Idle is performed by the coolant sensor, MAF and oxygen sensors. When the car starts, it takes a few minutes for the exhaust to heat up enough for the oxygen sensors do anything. Do you get better idle on a cold start?

You can jump the two contacts on the coolant temp sensor telling the computer that the engine is hot enough, although it's a $20 part that is simple to replace.

The MAF diagnosis is a bit tougher...

 

Does the XJS with an AJ16 have an adjustable throttle cable?

If so......

My 1995 XJR with the AJ16 6-cylinder was prone to high idling. Usually a dirty throttle body but one time the fix was as simple as adjusting the throttle cable.

Cheers
DD