How is everyone doing?

I have been driving my XJS as my daily for half a year now, with little to no issues. Wonderful experience all around, I must say.

However, this all changed when I took a set of tracks a little too quickly a month ago. Once across, the car would not rev over 1400 RPM, nor climb over 30 mph.

I have switched the fuel filter, and the fuel pump doesnt seem to be making any of the noises people mention hearing before it goes out.

Since the issue is abrupt, the car immediately quits revving at 1400, and repetitive, I assume that the problem lies with a sensor.

I have scoured the technical guides included when I purchased the ride, and find mention of a TDC sensor and maybe a Camshaft position sensor.

Are these one and the same?

Does any one have pictures or a detail of where to look to find them, as it can be a jungle in there?

Am I on the right track, or is it another issue entirely?

Thanks for all the help, I am really looking forward to getting it back on the road.

Cheers,
David

 

I suggest you eliminate the basics first:

Throttles opening properly?
All ignition connections tight?
All plugs firing?
All sensors properly located?
Fuel flow 100%? Fuel rail pressure Ok when you rev it?

Greg

 

Ummmm.....just how quickly was 'a little too quickly' ? Just a big jolt, or did the underbody impact the ground?

In either case a wiring connector could've been jarred loose. Lots of careful visual inspection needed here. Go with Greg's list and just start eliminating things.

If you hit the ground you should look for any physical damage that might account for the problem. Crushed exhaust pipe? Crushed fuel line? That's stretching a bit, but if you hit the ground, you gotta look.

As for crank sensors...

There are two crank sensors...IF your car has them at all, as 1989 model year was the transition year. If you have Marelli ignition, you have the sensors. One at the flywheel, one at the crankshaft pulley. Easy to see if you're under the car

If you have Marelli ignition I wonder if the jolt knocked loose coil or module wiring and you're running on just 6 cylinders?

Cheers
DD

 

Greg,

Thanks for the shout!

It's firing and turning over the exact same up until the 1400 rpm, so I assumed I could rule out ignition, plugs, and throttle.

I do not know about the sensors. As I think the problem lies there, do you have any operation procedure for checking them?

Doug,

The "quickly" was just a big jolt: no bottoming out.

I cleaned out the engine block today in the hopes of getting a clearer picture of what's going on.

How can I tell if I have the Marello ignition?

Thanks for all your help!

 

Any tips for a ramp or lift system I could get to help me access under the vehicle?

 

Sounds like your best solution would be to find a good local Jag mechanic.

 

Lucas ignition cars are pre VIN 157115 and Marelli ignition cars start after that VIN. If you have a square black box mounted on your intake manifold right by the throttle pedestal that has a Lucas sticker on it, you have Lucas ignition, if not you have Marelli.

I agree with seeking a Jag mechanic. Sounds like a tiny problem a mechanic could have solved in a couple hours.