Ok, so here's the deal. Bought a '97 Jag w/ 100k on the clock - seems like she's in really good condition, but the car occasionally won't hold idle speed at a light, or will stall / die completely when coming up to a light and braking too hard. I got a few engine codes ; but now my chk. eng light isn't coming on and the problem still exists.

I've cleaned the Throttle Body, the IAC, the EGR Valve, and replaced the Fuel filter as well as checked spark plugs (the tips were white). Also checked for Vacuum leaks and cannot find any.

Here are the engine codes: P0300 (Mult. random cyl. misfire) x 2 (meaning this code was logged twice) , and P1316. I cleared the codes, and the chk. eng light has not come back on, but the problem still ensues.

Any advice on where to go from here is VERY appreciated!

 

what if you try disconnecting the idle speed/air control valve as a test? of course the CEL will illuminate as a result...just thinking out loud

 

Thanks, I'll give that a shot. I changed spark plugs the other day with a friend of mine ; and all the tips were white (seemed to be gapped too close). Fitted a set of NGK spark plugs - and the car idles fine now at lights most of the time and doesn't die ; however it did it to me yesterday again but only once throughout the entire day. A huge improvement.

Apparently this problem is due to either plugs / or the coil packs. How do I test ea coil pack to make sure they are operating correctly? Does anyone have the service manual or a link to it?

 

Isn't dying at lights anymore, but the idle still seems to drop suddenly at lights sometimes - along with the voltage gauge going down a bit from 13v then goes back up with the engine idle speed.

 

My gauge drops slightly from 13 at a stop, too, but idle remains as it should. On occasion at a stop the battery light will flash for a split second, never to come on again throughout driving range. Nothing major in my opinion, at least for now as I have bigger fish to fry with the car lol.


Glad to hear for the most part its working well

 

The coil packs for each spark plug are apparently a regular failure item on the AJ6 and AJ16 engines. Intermittent failure could preceed final failure.

 

I swapped the coil packs around on the engine, and it's running much worse.... the idle goes fine for about (30-40 seconds?) then drops the idle down and runs rough. I am pretty sure at this point that i've got a bad coil pack in the mix. Voltage needle still does weird stuff at idle too, and i've noticed when I first start the car and drive off the headlights go from dim to brighter with acceleration. That could just be a loose serpentine belt not cranking the power to my alternator, since it does squeal a bit when cold, then goes away with the accel. Battery light never flashes... but the check engine light has been coming on now since changing the coil packs around. Any way to test these to find out which one is the bad one in the mix? I've pretty much narrowed it down to a #4 misfire however ; and I am still pretty sure it's a coil pack.

 

I had the same problem with my 1996 VDP with 110K miles. It would stall and not hold an idle. The problem was a speed sensor in the transmission. I am told this is a common problem.

 

KDross = could you say more about this? I have the same problem, have eliminated most other issues. Do you know part number? Is this the Input / Output Speed sensor? THANKS

 

Easy try is to clean the GB3 connector on the transmission body on the rear left side without jacking

Some have reported results in this low around gear shifting from park to drive regime

The connector is either a bayonet type connector that disconnects like a air hose connector or the common twist off , so don't try too hard to twist off

The ZF4HP24 transmission on the normally aspirated X300s has only the input speed sensor

The GM transmission on the supercharged versions has both input and output speed sensors

The fluid logic old school ZF4HP22 transmission on the 3.2L should not have a speed sensor

There have been reports of bad voltage regulator ( IN435 ) not maintaining a constant voltage and my theory is the ECU's ( transmission and engine ) do not adjust quick enough in the reference voltage thereby the sensor result that come back are not constant and causes a fault

Gazed alternator belt slipping ?

I keep ordering the IN435 but keep getting the slower response version , is this happening the new and rebuilt alternators for the X300 ?

 

I have two experiences with such stalling at idle and both of them were corrected very simply. Back around 165k miles my '97 XJ6 would stall at stoplights and such, sometimes it would go into limp home mode, sometimes it wouldn't. Sometimes it would start right back up, sometimes it would take 2-3 tries, sometimes it would take as long as 10 minutes before it would start again. This was back when I had just one car and didn't realize that to drive a Jaguar you need more than just one, so I drove with 2 feet for about two weeks, never really got any worse until one time it just wouldn't start at all after parking it. Killed the battery trying to start it and had to get it towed. Turned out to be the common crank position sensor which is very easily changed, no more problems.

I've found that it will also stall at idle speeds when both the battery is near dead, or just having been fully charged and reinstalled. It has a parasitic drain that doesn't really give me grief unless I go out of town, and thus if it starts upon my return, or if I just jump it, the battery is low and causes stalling at idle for technical reasons that someone much smarter than myself would have to explain. But more curiously a few weeks ago I returned from winter break, installed the freshly charged battery and on day two I experienced the same stalling, however it gradually went away. In both battery situations sometimes it would go into limp home mode, sometimes not.

All in all, I would look into the CPS and or your battery/charging system.
Good luck, hope this helps some.