Hi gents-

this is something that I have learned to live with, but I am trying to improve upon. Looks like others have had similar issues.

Car idles fine, does not misfire. On “P” and “N” the car will have a slightly choppy idle . No misfires. I feel a “dip” rarely, maybe once a year, but other than that the idle is just ever so slightly choppy on P or N compared to D. Barely noticeable, really.

My car has new OEM coils, plugs, injectors, regularly changed fuel filter, new CTS, CPS, TPS and a thousand other things I can’t even list because I can’t remember....It’s not a fuel pressure issue. It’s not a ECM sensor issue.......I know that @Doug had a similar issue on his AJ16 and tightening the intake manifold bolts seemed to help, and I also know that @Vee needed a new intake manifold gasket EBC11081. I can’t seem to find any other instances of a intake manifold gasket failing on a AJ16 engine on the archives, but the newest AJ16 cars are 24 years old now. It would make sense the manifold gaskets would fail......on the my daily driver X type it’s a mandatory maintenance item, but that’s another engine and another type of intake gasket(s)-and it’s a good 2.5 hours to do once you master it....but...

Questions:

1-Should replacing the manifold gasket be done at this point on the AJ16 cars simply because of their age?

2-has anyone done it? Does the whole thing have to come out, or can the manifold simply be pulled back a bit and the gasket replaced?

I am going to get under the bonnet tomorrow and see if the bolts are loose and start there.


Thanks !!

 

I don't remember the intake gasket thing....but my XJR/AJ16 ("The Tormentor") kept me very busy with running issues....and my memory isn't what it used to be

However.....

I do remember that the idle had some choppiness in P or N. Tipped-off by the experiences of others I decided to have the injectors checked. Here's the deal: at idle in P or N the engine load is the lightest it will ever be. The injectors are commanded to operate at minimum pulse width. In some cases, simply due to age it seems, injectors can become 'lazy' at minimum pulse width. The laziness results in erratic operation which results in a slight 'shop' at idle. This is not a Jaguar-exclusive thing.

Anyhow, I sent the injectors to David Faircloth to be checked. As I recall (more foggy memory) he said it was difficult to conclusively isolate such a fault but he did find something suspicious with a couple injectors. He sold me two new injectors and did his usual cleaning/servicing on the others. I recall the the chop in P or N went away.

You might want to contact him directly. His memory is probably better and lord knows he is more experienced on the subject than I am!

https://www.jaguarfuelinjectorservice.com/

Meanwhile, replacing the intake gasket can't hurt although I don't have strong confidence that it will help. If tightening, as you plan, gives some improvement that might be your sign to go ahead and replace it. I think you can just shift the manifold aside a bit to replace the gasket

Cheers
DD

 

Thanks Doug. I was referring to this topic where tightening the manifold bolts seemed to fix or alleviate your problem.

https://www.jaguarforums.com/forum/x...995-xjr-87601/

Since I want to tinker and see if I can get a perfectly smooth idle at “P” my only options at this point are probably to look into a slight air leak previously missed or start making new wiring harnesses for the injectors and the coils.

edit:

when I bought my brand new injectors from the UK I had them delivered to Mr. Faircloth from the UK so he could test them before I had them installed, as I wanted to make sure they where working properly...This was 203/14 I believe, but probably less than 10k miles ago