This starting happening occasionally a few months ago. Now it is happening more frequently and getting worse.

This happens any time of day, morning night and is not only at start-up or long drive.

While I am driving the car normally on the highway it runs just fine but when I need to slow under 10mph or when I am at idle the engine shuts off. Most of the time it is fine and idles correct but other times I need to keep my foot on the brake and the other foot on the gas in order to keep the RPM 1k to keep the engine from shutting off.

There has been a few times that during higher speeds, it starts acting up and the gas will lose power then quickly come back for a second then lose it again. This oscillation of power will continue until I turn the vehicle off and back on resetting everything. Sometimes I have to do it at higher speeds! I know its not good but I have no choice.

OBD Scan shows no codes

VIDEO NOTE: I meant to say 1K RPM not 10k RPM. LOL!!

Below is a link to a video I took when it was happening. The acceleration in idle is me keeping it over 1k.

 

Had an on off coil pack fault on my xjr that did the same thing. No codes but rough idle and stalling from time to time. Try taking the packs out 1 at a time to make sure you have good spark on them all. Short of that there is are a lot of idle/ stall issues on here that will be able to point you in the right direction. Happy hunting

 

The video is "private" ?

Anyhow, yes, a faulty coil is a prime candidate as far as guesses go.

Cheers
DD

 

Sorry about that. I should have tested it. Let me know if it works now.

 

Is there any way to know which coil pack it is? It only happens occassionally. MAybe I should just replace them all? Thanks

 

easiest way is to remove the coil cover then start the engine and remove each coil one at a time. if it gets spark its working. if you remove one and nothing happens or the idle doesn't change then that could well be the problem

 

Hello AL5001, my first post in the X300 forum although I have 'known' DD for a long time!!
I had a similar problem on my XJR6, it almost sent me potty as it took a long long time to figure out what the problem was.
What are the spark plugs you have? From my experience, the cross reference charts for different manufacturers are not always accurate, I found that some plugs I put in which were supposed to be a direct equivalent to the Champions made the car run terribly, it wouldnt idle at all. The heat range has to be bang on.
Is there anyway you can record the real time data? When I had a similar problem the diagnostics scanner did not throw up any codes, it wasn't until I took the car for a drive, with the scanner plugged in & my eagle eyed 11 year old watching the various figures (while I was asking him for various bits of info!!) he asked what does OL & CL mean as it kept switching between the two on a very regular basis. It turned out that the engine temperature sensor was goosed and sending incorrect info to the ECU resulting in the switching between Open loop & closed loop every few seconds. A £10.00 sensor & the car ran like new!!
Lastly, I havent got any equipment for testing for vacuum leaks. I figured by fitting a rather large 'bung' to the air inlet and pumping low pressure air from a compressor, by squirting leak detector spray (the type plumbers use for gas leaks) over the various joints, any leaks should be shown up. It was surprising how many big bubbles appeared, all over the place!! In places you wouldnt imagine. I dont for a minute think they would have a major effect on the performance but I'm sure they must all add up.

Hope this was of some help, don't get downhearted!!

G