sorry to post so late, But if any one suspects the stepper motor as a problem.
AC-delco makes it.
Part#217-1765 about $46.00 vs. 274.00 @ the dealer.
hope this helps.

 

mirage1, I couldn't find AC-delco stepper motor Part#217-1765 online. Could you provide a link to the store?

 

i have a 1996xjs some times on the inital start it will fire up and run smoothly... If i start and just quickly engage the starting motor and release he key it will start and run very rough and stall out. When this first happened i thought it may be dirty fuel so i kept the tank full at all times. This seemed to work but just today it is miss behaving again. on first start up of the day it will usually start and run very smoothly . If i turn it off and re start it will usually burp and fart and run very roughly. If i keep the gass to the car it will run fine but if i let it idle at at light it will stall out... any help is greatfully accepted.

 

I have the same rough idling problem. not on every start up but on more and more it seems. worst if i do not let the motor fully engage after starting. If i release the strating motor too soon it seems to start but run rough. Then i have to wait an hour or so for another clean start... were u able to get your car running

 

has any one had any luck in solving he rough idling with the xjs.... I have the same issue not on every start up but betting more frequent....

 

There's no single answer. The previous replies in this thread give some idea of the possibilities. Do you know if any of them have already been explored/tested/eliminated on your car?

It might be best to start a new thread. Adding new questions to multiple older threads gets confusing.

Cheers
DD

 

I've gone back and reviewed all the suggestions and it seems that I've tried every one of them at least once. I truly am frustrated with this rough idle problem. The only thing I tried again, that seemed to make any improvement (but did not solve the problem) was removing the EGR valve and blocking the EGR seat with a metal plate and plugging the vacuum hose. It seemed to smooth the idle out slightly. It also raised the idle to about 900 rpms, but still idled rough. I could lower it, but it doesn't seem to be a big deal and maybe that is why the idle is running smoother.
I'm in the process of trying to find a jaguar mechanic that also has a PDU or equivalent to maybe work on my car for me, but I'm very tired of paying mechanics for not solving the problem. They always find something that needs to be replaced or repaired, yet the rough idle has never gotten fixed.
I live in the south suburbs of Chicago, so if anyone has a truly reliable and knowledgible jaguar mechanic in this area, please post there name and business number. thanks

 

Hi all,

I was having a low idle issue at stops that caused it to shut down. With a new battery it would start right back only to stall out at the next stop. I looked through several of these threads and did the suggested contact cleaning of several sensors. Just got back in from a long test drive and BOOM! the car ran great. No stalling.

This is a great forum that I would have long since been too frustrated with my XJS to keep lest the info provided here.

Thanks!!!!

Tony in NM

 

a bit late to the party here... but though i would add that my 1990 3.6 had the same problem, for example, when coming to a stop, the rpm's would surge. the problem was the rubber boot between the air filter and the MAF. on the underside it had been bitten into by the jubilee clip causing a leak. i hope this helps someone out there

 

Thank you all - hope this helps.
Thank you all for all the information to make this a good adventure in Jaguar owning.


So I thought I would share something that is probably embarrassing but I could see it go un-noticed.
Short Story: Cyl 6 and Cyl 5 coil wires are really easy to mixup.


1995 Jaguar XJS 4.0 6 cylinder AJ16
24K miles.
Was changing spark plugs, because fuel consumption was sub par / could feel it wasnt purring exactly right.
NKG copper -- tried .025 and .03x gaps -- rough idle, returned them.
The Champions I had in there were actually not bad, but they were gapped by last owner at.035.

Put the original champions in -- rough idle.
Changed them to .025 gap, and cleaned everything.
-- rough idle.

Stood there and realized that #5 wire and #6 wire to coils are same length, and #5 (so it turns out) actually came out of the harness behind the #6 wire.

So that's it. not only was this solved by switching #5 and #6 wires, but at .025 gap... .. well its just right, and gunning it, it was a whole new beast.


GL,
David

 

is cylinder 6 the one closest to the radiator?

 

I consider cyl 6 to be towards the windshield and cyl 1 towards radiator.
Apologies if that's wrong but just a habit.