So I've had this ongoing issue where my 2000 s type 4.0 idles roughly. It's not super bad but its enough to be annoying. I'd describe it to be almost like a cough. Sometimes it's worse than others but it only happens when the car is warm.
It was recently in at Brakes Plus and they offered to run a diagnostic which they said pointed them to the computer system which they could not run any test on because they aren't a specialty service center.

Has anyone experienced anything like this? I'm pretty sure my only option at this point is to bring it to the dealership and pay whatever they ask me to.
Thanks so much!

 

You need your own obd2 scanner to own a jag , and watch fuel pressure and fuel trims! So was there any codes ?

 

Yes. There were 2 cat codes which concludes its probably an air fuel mixture issue. However, if it's an issue in the computer system is there anything I can do about it my self? I would assume only Jaguar could mess with that stuff.

 

+1^Datasports^ Get a code reader and learn how to use it. They are inexpensive. Look at the Elm327.

Don't overthink this. If the codes suggest a fuel mixture issue, that's where you should start troubleshooting.

You should consider the dealership the option of last resort, as they can be very expensive.

 

Not going to be the computer(s). Last thing(s) to suspect.

Get an OBD tool with live data. Check for codes, then sensors for plausibility and then fuel trims.

Which cat codes? I mean... want us to guess?

If ignored and it's one of the usual issues then you'll ruin the cat(s) when actually they used to be fine.

 

The reason why I say the issue is in the computer(s) is because brakes plus ran a diagnostic and determined it was. They obviously ran through all of the o2 sensors and such so acoording to them the issue is in the computer which they can't deal with since they are not a specialty dealer.

 

They're guessing, then. Fair enough but likely to be wrong.

You want to DIY if you can or a jag indy. Liable to be very expensive otherwise.

 

I actually don't know off the top of my head. I do know that breaks plus ran a diagnostic and determined that the issue was in the computer some where but they are unable to tell exactly since they are not a specialty service center.

 

As it's the 4.0 the big (huge) thing to worry about is timing chain tensioners. If not replaced - and they almost for sure haven't been - sooner or later they fail and write off the engine (and thus the car).

The reason the cars are cheap to buy is that DIY is almost a necessity for the costs can be scary otherwise.

The only real alternative - at far more cost - is a jag specialist. The other places are almost worse than nothing as you're finding.

 

Is it possible to DIY timing chain tensioners? I've done plenty of things to the car by myself Engine coils, spark plugs etc, but the timing chain is inside the engine with an oil flow system that I could imagine would not be easy to do.

 

There are step by step guides with photos on this forum of how to do it . And I'd say jtis will cover it too ! It just time and patients and a couple of special tools ! If your not comfortable to learn on the fly then find a knolagable and trusted mechanic other than jaguar who is willing to perform the task , but realy there is no reason that some one who can change spark plugs can't at least remove the cam covers to inspect them to see if thay are indeed plastic or alloy tentioners . Also guides on the forum to show you how to check them ! I also doubt that your computer is at fault for your electrical gremlins by the way!
Very unlikely .

 

Well thanks for the advice!
So do you think the rough idle is due to a timing chain issue? Maybe I have too much faith in brakes plus but I feel like they would have caught that during the diagnostic.

 

nope i don't think that will be the cause . but certainly something to be aware of and be proactive about!
you need to watch fuel trims and watch all the sensors functioning , so you need your own obd2 scanner to do this ! don't keep driving it in the mean time or your cats will be toast! or they may already be ! witch won't help any thing
it could be so many things , fuel pressure regulator , fuel pump spiking, or any one of the sensors so you need to monitor them asap !

 

I have the same problem in my 4.0 S-type. My problem is a ignition coil, or a faulty spark plug. (It does need a tune up) Scanned by my own tool and it picked it up. Sometimes giving a Catalytic code due to the un-used fuel from that cylinder going to the cat