Hey Lads,

Been experiencing some running issues recently and was wondering who may have had similar things happen to them?

The primary issue was detailed in another thread but to summarize, the car would start and run perfectly and then completely random, you would hit the gas pedal from a stop sign or whatever and the car would stumble badly and most times stall out. Restarting the car would sometimes clear it up and other times it would not. Same stumble every time you put the thing in gear and tried to move forward. When this wasn't happening, the car would run perfectly.

So yesterday I took the car out to see if I could get it to do the stall and stumble and it didn't disappoint. Stumbled as soon as I tried to drive away but I caught it before it stalled. It was then running slightly rough. I left it in gear a blocked the front wheels so I could listen more closely in the engine bay while it was in stumble mode. It was certainly running rough as the engine was wobbling back and forth and normally you could almost put a glass of water on the engine without making waves.

Here was the completely weird thing I noticed while looking into this. I had the AC system running which normally triggers the fans to run continuous. However, what I noticed was the fans were cycling on and off. They would kick in for about 10 seconds and then start to shut off. Before they could come to a complete stop, they started again. This went on and on.

Finally, I shut the car off and waited a couple of minutes and started it again. The stumbling was gone and when I turned on the AC again, the fans started and ran continuously like they always have. So maybe the issues are related or maybe they are not but it seems weird that these two things happened at exactly the same time?

I also notice that my alt gauge moves around quite a bit. IIRC, it used to sit pretty consistently at about 13.5Volts but recently I have noticed it dip below 13 at idle and then come back up when the accelerator is pressed. This is usually with the AC running. For those of you in similar hot weather like I am in Vegas, does your meter drop below 13 routinely when the AC is running?

I guess I am just curious if anyone has had the same conditions and if not, do you feel that the two problems could be related? What could cause the fans to cycle like that anyway?

Hope someone has some experience.


Bernie

 

My guess would be a ground cable moving as the engine moves on it's mounts when you put it in gear. Maybe try removing and cleaning the connection ends and tightening it down?

 

If the ignition coils are arcing and disrupting the ECM you will have issues like this.

Check for on-plug coil problems with a search of this forum.

bob

 

Thanks Lads,

Looks like a little review of the ground points are in order.

Also looks like the coils could still be a culprit.

Wish I could get my hands on a used set to swap them out for a bit and see if the issue resolves itself. Don't wanna be throwing that type of coin at the car if that is not the problem.

Thanks for the replies. I will update when I get a chance to eliminate a couple of things.

Bernie

 

Let me look in the AM, I may have a few good ones in the garage, if so I'll send them on to you. I sold my X300 in favor of an XJR-100. Gave the new owner some extra coils but I may have a few left. I'll LYK

 

Found two NIB ones from Welsh Jaguar, LMK if you want them, you pick up the postage, the coils will cost you nothing.

 

Very awesome of you.
However, I found a used set of coils here in Vegas yesterday and swapped them all out. The problem remains.

At first I thought it was all good. Drove the car around for a while and didn't immediately have any issues. I then took it to the car wash and as the guy was driving it out of the wash, I could hear the exhaust making a fluttering sound and then it stalled. As I stood there, he fired it back up and there was sound dark smoke coming from the exhaust on startup. Unspent fuel I assume? It stalled again. He had to start it a few times until he finally got it in line for a wipedown.

The other thing I noticed was on the drive back to the house, the engine was not being responsive. I floored it a couple of times and it wasn't making much power at all. I am going to test it this morning from cold and see if it is still down on power.

I have read that it can also be an issue with the crank position sensor as these seem to be another part on these cars that has been known to cause running issues? Since there are so many new parts on the engine and the CPS has never been changed (by me), maybe it makes sense to swap that out to see if it makes any difference? I might be able to grab a used one from the same guy I got the coils from.

Bernie