A Big Thanks to all who responded to my previous posts!
 

So the no start problem was resolved with a new crankshaft positioning sensor- I was super excited to find and fix the issue, but I wasn’t 100% convinced at the time I ordered the part that it would be that simple - I cheaped out and bought a super inexpensive one ($25) to make sure that was the issue -instead of the paying $100-200 for an OEM part I wasn’t positive was the issue. The first drive or two it ran perfect with 25 CPS now it’s running rough and sucking gas - I am assuming CPS got hot as it isn’t a quality part (or something happened that made it less effective) and it won’t last long and my mpg will suffer until I replace it?

My question is what happened? Why? And should I change it immediately?

Should I get the part from a dealership and pay 200 for best and/or 100 for an off brand OEM? Would I be cheaping out again by grabbing a $60 CSP from partsgeek?

Thanks,
Shannon

Opps forgot to add: 95 XJS 2+2 6cyl 4l

Hi Shannon

What Car do you have? (make and model etc)

95 XJS 2+2 6cyl 4L
 

Thanks for pointing out my omission!

The CPS will have no effect on how much fuel the ECU commands. The CPS tells the ECU what RPM the engine is doing and when to fire the ignition and injectors.

Fueling amount is controlled by feedback sensors MAF, MAP and TPS, I am not familiar with the I6 but I have heard of issues with the MAF, this would cause fueling issues and this is where I would start.

Hi Shannon

I've got exactly the same Car as you, a 1995 XJS Convertible 4.0L Six Cylinder Automatic with the AJ16 Engine and while I know my way around an XJS V12 which is in my other Car and is the one that I use the most

I knew absolutely nothing about the AJ16 Engine as I have never laid a Spanner on one of these in my life, or any other Jaguar Six cylinder for that matter but having replaced the In-Tank Fuel Pump (which I regard as being the Job from Hell)

(As you have to either remove the Fuel Tank or at the very least, be able to slide this back enough in order to get to the Pump)

I was still unable to get this Car Started and to tell you the truth I was totally lost and didn't know what to do, so I ended up doing the sensible thing and putting out a 'Cry for help' on the Forum

Where I was very pleased to say the Suggestions kept on coming, including a recommendation to buy a New CPS Crank Position Sensor for which I paid £50 but still 'No Dice!'

And so in Total desperation, I went right through the Car and tried 'every trick in the book' which included Six Brand New Injectors! and you really, really, really, don't want to know how much I paid for those!

'Only the best for my Baby' but still this Car wouldn't Start! although I stopped short of buying 6 New Spark Plug Coils, as for one thing or should that be Six things! I had Six good Sparks from all the Plugs

And then I even got close to the Nuclear Option, of the possibility of buying a New Ecu, which was just one away from insanity, as they are so expensive that one way or another it was going to end in Tears

But even so I ended up taking out the ECU and then Cleaned all the Plugs, only to find that it still didn't make not one jot of difference, at which point it crossed my mind to hit the bottle of Absinthe all over again (Don't try that at home Really Don't!)

And then along came 'Paddy' from, 'ahem' another Forum who knew exactly what the problem was!

Where having followed his advice and then done what he told me, the Engine Simply Started on the Button, where She has been running like a Bird ever since!

Though while I am not saying that this will fix the problem that you have, since this Fix is a Free one! then it is definitely worth a Shot, as in this XJS game, you never, never know!

Ok so here it is!

Open up the Cover of the Fuse Box, underneath the Knee Pad on the Passenger Side of a (UK) Car, where you will see a multitude of fuses, except on this occasion these are 'Not the Components of Interest' But instead look Upwards!

Where you will see a Couple of Blue Relays, where if I remember correctly Jaguar recommended swapping out for different make that had thicker blades, or at least removing them and then reinserting them back into their Sockets, which I did

And then 'Hey Presto' as if by Magic! She Started!

You can read all about this including Photos on Page: 96 of my 'Cherry Blossom' restoration thread and here is the link

'Paddy's Miracle Fix' for my 1995 XJS 4.0L That refused to Start no matter what I tried!

But if you're Short of 'Bedtime Reading' and want to read the Full Saga of how I tried every trick in the book including all the Photo's (Ecu removal/Coil Removal/Injector Removal/and lots of other Stuff, then you can find that in the link below

Including Fuel Tank Removal and Fuel Pump Replacement and of course 'Paddy's Miracle Fix, which eventually Won the day!
and I will drink to that! (or just maybe on Second Thoughts I Won't!)

You can find it all there somewhere, from Page: 93 to Page: 96

Every Trick in the Book to get 'Carmen' Started (well almost!) with her AJ16 4.0L Engine that I had never ever worked on before

LHE1640AA is available from JCP for 107 dollars plus shipping. I honestly would not keep a 25 dollar CPS in the car. It’s a maintenance item anyway.

As as far as the car running rough and sucking gas as you describe, that is hard to pinpoint. Do you have your check engine light on, and if so what is the code? I know my car (a 95 AJ16) can have codes stored which do not trigger the light. I would recommend you plug in a OBD2 reader and see if any codes are stored. You could have a bad coil, you could have corroded pins in your ECU. Is it shaking, is it misfiring ? Let us know