I have a 95 xjs conv with 74k miles that has been well maintained. Experiencing rough idle and occasional stalling when stopped. Ht still in D. Air fkow meter was checked? Eci was checked. Fuel filter w replaced and carbon induction cleaning of the engi e was do e? Idle is still very rough and dips randomly.... I had car at, ocal nag specialist who see,s to have ruled out any major issues but we are scratching our heads!! Any thoughts on how to correct?

 

Sorry for the typos above....keyboard problem....... the idle is very rough at red lights and often dips low or stalls. Jag specialist ruled out anything bad but couldn't figure out the issue.... does anyone have any thoughts? Eci was checked, air mass meter is OK, fuel filter is new, fuel pressure is OK. Car is in great shape but idling issue is driving us crazy

 

There are a lot of things that could be causing this, and the AJ16 management system on the 95/96 is not good at setting a code so you really don't know what is failing.

First the things that won't cost you to do:

1-remove the throttle body, remove the TPS at the bottom and soak it with cleaner, clean the tip of the ISCV Also clean the trunk after the MAF, you will find oil that "breathes" from the engine. While you are at it also look for vacuum leaks.

2-Remove the EGR valve and clean it. Sometimes so much carbon builds up it stays in the open possition and causes stalling.

3-Carefully clean your MAF sensor with MAF cleaner

4-Check your ECU connector for signs of corrosion or build up (water drips in there and can cause problems

5-Make sure that you have perfect ground flow at the connectors in the trunk, the ones on the firewall and the ECU.

Things that will cost you but tend to go out on these cars commonly

6-Crank possition sensor- they slowly fade out and cause sporadic problems-may cause what you are describing-this is should be replaced after 70k miles on these cars anyway.

7-Coolant Temperature Sensor-ditto as above-should be replaced-make sure you have the correct part.

8-Throttle Possition sensor-when mine went out it would cause to stall at stops and sometimes in the middle of the freeway while driving...like someone had just turned of the car in the middle of driving-again very difficult to diagnose, mine was tested and came up as "good" until I replaced it on a gut feeling. These go bad often because people don't ever do number 1 and since they are attached to the bottom of the throttle body oily residue eventually drips in it and kills it.

9-Ignition coils- I doubt this is the problem in your case, they will typically cause a random misfire, like a dip in idle every so many seconds.

Then there are other things you could look at like fuel pressure regulator,fuel pump etc, but I have yet to hear on one going out on a Aj16 powered XJS
L
sorry for the long write up, hope it helps.

 

I had the exact same issue. First I stalled out on a road and I got a code to replace (or service) the EGR Valve. Took care of that and things got better...until they got worse again.

I took it to a Jag Dealer and for $150 they told me that I needed to have the Throttle Body replaced for $2,400 and that since the TPS typically gets damaged when they pull out the throttle body, they needed to add another $800 for a new one.

I took it to my local mechanic and told him what the Dealer told me. He charged me $50 to clean out the throttle body. It took about 500 miles before the symptoms you mentioned to go away completely, but they did.

Replace the EGR and clean out the throttle body. Drive it around for awhile and come back and tell us how it's going.

 

I am not an expert but EGR valve is for emission control. I don't understand why it would effect idling.

It really like either MAF sensor or TB. Have you tried disconnecting the MAF cable and see if there is anything change?

 

If the EGR valve is stuck open, it will essentially cause a vacuum leak, leading to inefficient combustion, rough idling, hesitation, and sometimes stalling in extreme cases. This is because the car cannot combust on carbon dioxide from the tailpipe — it needs atmospheric oxygen.

 

Car seems to have gotten worse. stalled at every stop and barely driveable the other morning. Now it is driving okay, but engine has slightly louder sound an a knocking or 'putting' type sound.... a bit rougher like a diesel...... Problem is finding a good mechanic here locally in Maryland area (Metro Washington DC Area). The last jaguar "specialist" is the one that made the car worse.... Also, forgot to mention that oil change was done at same time as carbon induction cleaning.... car sounds worse than ever. Gorgeous car, but doing no good for me in the garage!!!

 

I think you're overthinking this with a Jaguar Specialist. What you need is a good mechanic.

I use Cherrydale Motors, right across the river in Northern Virginia. As I mentioned earlier, Jaguar wanted over $3,000 to fix my problem. I took it to Cherrydale and they cleaned up my throttle body for $50.

Did you have anyone clean the throttle body yet? I don't believe a carbon induction cleaning will have the same effect. You need someone to unbolt it and give it a good scrub down, the old fashioned way. It's really quite simple to get to and you could probably do it yourself this weekend.

I'd assume if your EGR Valve was the cause of this, you'd have seen a code by now, but I'm wondering if you did anything with that either.

I used to take an old car I used to own to D&D just outside of Cheverly. Those guys were absolutely fantastic at fixing my car, or showing me how to do it without charging me when they could. If I still lived near there, I'd still be going there, but I moved to the Virginia side.

I've attached a photo with your engine identifying the parts. That should help?

 

Hello, sorry to hear about your ongoing problems. Have you had an opportunity to check any of the things I mentioned above? I have the same vehicle as you do and these are things that typically come up on the AJ16's.

 

NOFIS, the AJ16 engine is no different than any other engines. It's just like the Mercedes and BMW engines I used to maintain. I don't think you need to look for a Jaguar specialist. Like Vee said, you just need a good mechanic. May be you can find a good mechanic at Yelp.com.

 

thanks for tthe phot but for some reason, it says i dont have permission to view it. also thanks for the tips. i will let you know how i make out...

 

So, i finally heard back from my mechanic today. He says that the Stepper Motor (Idle Control Valve?) is bad and needs replacement. HE also said spark plugs were all gunked up...... Lastly, wants to replace my Cam Cover Gasket........ Anyone have any thoughts???

Let's hope this cures my stalling issue....

 

The Jag Dealership wanted $800 to replace that stepper motor. Can you tell me what your mechanic wants?

I still believe that you must clean out that throttle body. If its not the TB, or the EGR Valve, then my third guess would be the stepper motor, but I believe you may have to take it to the dealer to have it properly set. Your mechanic will need a piece of equipment to calibrate it, which I don't think he'll have.

I'd go back to Spikepaga's post and move from there.

I hope you have access to the picture I posted by now. You'll find that the throttle body is easy to get to, easy to unbolt, easy to clean and easy to replace.

Its your cheapest option.

 

VEE-
Throttle body was cleaned approx 1000 miles ago when the hesitation first started. EGR was supposedly checked and ok..... The car is being serviced by top line jaguar over in Springfield VA. (check them out at www.toplinejaguar.com). They supposedly only work on Jags and have all of the physical and diagnostic tools to handle jags, old and new..... I will let you know how it works out. They seem very atttentive, customer service oriented, and reasonable....

 

Don't be surprised if the report comes back saying a coil or two has gone tango uniform.

I'm living that right now with my XJR. Replaced two duds a few weeks ago and now have three more going south.

My symptoms were/are rough idle, stalling at idle, extreme engine roughness on start up.

Cheers
DD

 

Top Line? I didn't think they really existed. I sent them a couple of emails asking for some info on what they could do for my XJS and I never heard from them.

I may drive down there and take a look.

I don't recall that you mentioned the TB was cleaned. I remember that carbon induction cleaning you mentioned, but I don't believe thats the same. Carbon Induction Cleaning, to me, sounds more like someone just dumped in a bottle of something to clean something out. I was talking about a good old fashioned hand cleaning.

Please keep me posted though. I was where you were at one time and considered myself lucky to have had such a simple solution.

Thanks.

 

A couple of things;
ISCV will typically cause high idle or low idle on these cars, not stalling (although it might if the idle gets low enough). I know you are saying these guys are specialists but do you know for a fact that they have the specific computers required for the 95/96 XJS AJ16 and actually work on them often?....Remember that a 94 AJ6 powered car is not subject to the same ailments as a 95/96...my point is that just because they have cars that look like yours does not mean they know an AJ16 from top to bottom.

I once took my car to a know "Jaguar specialist" to clean my throttle body as I do or have done by others periodically, and he said my throttle body was missing a gasket and that he was going to adjust the idle thru the adjustment screw........I said "thanks don't touch anything else on my car and bring it around". The AJ16's don't have a gasket and the idle is not adjusted via screw.....but I digress


My best advise to you is to print out the list I and others have posted and take it to your shop.

Owning and maitaining these cars is very easy but it requires a lot of owner involvement as far as being informed is concerned. The resources are out there it just takes time.

I agree with Vee that an induction cleaning is not the same as removing the throttle body and doing a proper cleaning.

Good Luck

 

NOFIS,

Any progress/update?

 

Top Line Jaguar got her running again. The stepper motor seems to have corrected the stalling. The throttle body was also cleaned. Definitely running much better. key word is that it is RUNNING!!!! UNfortunately, idle is still rough.

When coming to a stop (i.e at a stop light), the RPM initially comes to normal 600-700 level, then within seconds, it dips down to 400RPM and right back up again.... Also if idling for a long time, car does this routinely (sounds like it is going to stall but quickly goews back to normal...

Any thoughts?????????

 

NOFIS,

After I cleaned my throttle body out, I experienced the same issues you did, some random throttle adjustments on slow, or stopped traffic, but it got better. Its almost as if the engine has to figure out how to play with your replaced, or clean, components again. I forgot how long it took before this totally went away, but it was a few months. It did happen less and less over those months though...

Glad that they solved your problem. Can you tell me what they charged you to replace your stepper motor (and clean the TB)? I'd just like to know how iit compares with the *******.

Thanks.