Hello everyone;

I posted this on the other Jag forum and have gotten some great advise so far:

My car has suddenly started idling a little rough, it's not constantly missing or anything, but its definately not as good as it has been......

The car has:

1)Six new Jaguar fuel injectors
2)Six new Jaguar OEM ignition coils (2 years old) since I happen to have another brand new boxed Jaguar coils, I replaced them. no change. Definately not the coils
3)New Jaguar MAF
4)Replaced the NGK spark plugs with Champions 12rycc no change.


At about the same time the idle started degrading, I noticed that the charging light came on a couple of times while driving at higher speeds, and also that the voltage gauge is dropping very, very low, (more than normal) at a stop with the A/C and lights on and my foot on the break.

The alternator is about a year old, an OEM Bosch unit

I replaced the battery monday and no improvement ocurred. However the car starts perfectly fine.

Do you guys think my charging situation and my idle situation are one and the same ?.....Could a poor charging situation cause idle issues like the one I described??

I am thinking I might have a bad harmonic damper or maybe the belts are a little loose.

Thoughts please?

Thanks !!

 

I have three suggestions:

1. Clean out your EGR Valve
2. Clean out your throttle body
3. Check to see if you had TSB 17-11 performed on your car. If so, I found that the "restricer (Part # NNB3956AA) had split in two along the seam. I glued the two pieces back together with some epoxy and clamped it together so it wouldn't happen again and put it back.

Worth checking into.

 

Thanks for your reply Vee

1-New-checked it anyway. Clean
2-Throttle body looks like you could eat from it
3-TSB 17-11 was done

 

And keep your eye on your alternator - they can crap out gradually; watch the volt meter in your instrument panel.

 

In that case you need to check the added restrictor. Or whatever you want to call that egg shaped plastic part that was added as a part of this TSB. In my case, that plastic part had cracked so the hoses really weren't connected the way that part was meant to connect them.

It shouldn't take you long at all to inspect that plastic part.

 

its intact. My problem is electrical for sure. I am also having what seems like the A/C temperature being turn up and down while driving, and I have stared at the pulleys with the car on Drive and handbrake on to see if there is any slipping or noise coming from any of the pulleys locking up and I can not find any. I think the electrical problem is messing with everything.

Please look at this video:

XJS VOLTAGE - YouTube


The voltage is stuck at 9 volts until I hit the break and suddenly it pops back up to 13.

I spend a lot of hours Saturday cleaning and tightening grounds, but no joy

 

everyone on this forum needs a vacuum gauge. your just guessing without it.

 

My 95 XJS was stalling at idle. Just removed and cleaned the Throttle Body and replaced the TSP ($285). It is all pretty straight forward. I guess ideally one would also remove the intake manifold and clean it. Mine is nasty inside, but I wasn't the adventurous. If you plan to do this but not replace the TSP, I would at least remove it so carb cleaner does not get into it. Good Luck
1. 2 radiator hoses on bottom of TB. Disconnect the forward hose first. Have a plug ready. on reassembly do this hose last.
2.Be very careful withe bolts holding the Idle Control Sensor. They are very soft and round easily(as mine did)
3. Idle RPMs will bee all over the place after job is done, but will settle down after a couple hundred miles (i guess it takes the ECU a while to figure out what's going on).