Its likely a bad coil or two that's intermittent with the issue. I had the EXACT same issue with my 96 VDP 4.0L.

You can get the parts from Rock Auto for 65 dollars each.
While you're under the hood replace the plugs too, a misfire would have fouled the plugs up and they're around 3$ each so it's a cheap fix

Try that out

Cheers,

Mike

 

Had this problem on mine when I got it new coil did the job

 

97 VDP. CEL flashes and remains on. Have codes p0300 and 1314. Changed o2 sensors (all),plugs, all coils, and forward cat.
New to Jaguar and this forum. Did not want to start new thread. Anyone that has suggestions on where to look next would be appreciated. Also unplugged MAF sensor and car ran the same. Car lopes at idle like i'm in a boat. Very sluggish on takeoff and then gets up and goes. At speed car will slow a bit and then take off. Without any gas pedal movement.

 

Codes for a 97 are on page 121 as you have a AJ16 engine

http://www.jagrepair.com/images/Trai...20-%202000.pdf

The O2 sensors need a good ground to shield the sensitive return wire from external interference

There are 2 ground terminal post for these wires on the upper firewall left and right

The O2 sensor connectors can get corroded and also swapped as they will fit each other

The middle wire on the TPS will read 0.60 volts DC at idle mechanical stop

If you rotate the throttle by hand slowly you should see the voltage smoothly rise toward but not to the reference 5.0 volt DC

You should not see the voltage bip to 0

Do not adjust or replace this sensor just yet

The MAF middle wire will read 1.2 volts DC at the correct idle speed

As you run the engine you will see it rise toward but not to the reference 5.0 volts DC

If any of these 2 fail at some point of the engine range the ECU will discard the data from it and revert to a less then optimal set of data maps and then revert to normal operation if the sensors comes back in range

Check to make sure the TPS connector is locked on with the metal bar , ask me how I know

New cheap coils can add new problems in engine regulation , did you save a couple of the old ones ?

 

Thanks for the input ! Will check out the voltages you supplied. All old coils are saved. They all measured .8 ohms. The new ones measured 1 ohm.

 

You can follow the TPS middle wire up and over the fuel rail and nick the insulation to get your readings

It's the only Green / Yellow wire in the bundle

 

Hi jslade57,

I am attaching the DTC Summaries that gives the definitions and many possible causes of each code specifically for your model. Here's what it has to say regarding P0300 and P1314:





If you recently purchased fuel, it may be contaminated with water. That is one of the most common causes of sudden misfire onset.

Another very common cause is cracked or missing insulation on the coil wiring, especially at the rear of the cylinder head where it bends.

Note that the P1314 code (and the flashing CEL) indicates that the misfire rate is so serious that the catalytic converter may be damaged by unburned fuel, so you don't want to run the engine any more than necessary. Also note that while P0300 is a random misfire code and does not point to an individual cylinder, P1314 points to misfires in the rear three cylinders.

Are any other codes present, even ones you do not think are relevant?

Cheers,

Don

 

Hey Don ! Thanks for the reply. This problem has been going on through several fuel purchases. Have not changed fuel filter yet. Per Lady P the O2 sensor connectors are in good shape as well as the wiring. No other codes besides these i have listed, and the CEL lights up quite promptly when i start the car. Checked coil wires and they are solid. Have not looked into the TPS yet. Caused myself further problems when checking MAF sensor voltage today. Saw a large lug attached to drivers side firewall. Assumed it was ground and put pos meter lead on middle wire of MAF sensor and neg lead on that lug. Large lug was not ground. Being new to Jaguar i would not have figured battery voltage tlo be attached to the firewall. I expect i likely damaged the MAF and i have ABS lights on too. Put everything down and went in the house..will continue tommorrow

 

The 1.2 volts DC at idle on the middle wire will let you know it's alive

ABS not electrically connected

You are going where few have gone before

 

ABS not electrically connected ? Don't understand what you mean.

 

The ABS wiring is independent and nothing shared of the MAF wiring

 

OK thanks for clearing that up.

 

Since the coil wires are wrapped toward the rear of the cylinder head, it may not be possible to visually detect an open or shorted wire. You can do a basic test of wiring integrity by connecting your voltmeter to each coil's voltage supply wire (White/Pink) and a good ground, turn the ignition to ON but do not start the engine. There should be battery power at all the coil connectors. While watching your meter, gently flex and manipulate the harness to see if the voltage is interrupted. I say "gently" because you do not want to damage insulation that is brittle but not yet cracked.

The coils are grounded individually by the ECM, so testing the ground side wires is more complicated. But typically, if a ground wire has a problem, a supply wire will too. If you discover an interruption, unwrap the harness and repair the damaged wiring.

Cheers,

Don

 

Checked 4,5&6 since the code points that way. Voltage stayed rock steady at 12.05. Coils measure .9 ohms.

 

Your static battery voltage is low at 12.05. With a healthy, fully-charged battery we would expect 12.6 volts or so. Probably not related to your misfires but something to put on your list to check.

Is there oil in any of your spark plug wells?

Cheers,

Don

 

Ya battery is a touch low but i dont expect it is effecting current issue. No oil in the well, however, the #2 plug had some oil on the threads when i just recently pulled all plugs. Cleaned the well but found no oil there. The plugs were'nt dirty but i gapped them and cleaned them anyway. Any idea what kind of resistance values i should find between the pins on the MAF sensor ? Need to carefully check this sensor after applying 14vdc directly to it by accident yesterday. May go out and have another look today. Not lazy. Its really hot out there and i struggle due to rod in rt thigh running hip to knee and 8 screws in knee, 4 bars in rt ankle with 16 screws (crawling under car is a project itself) and stage 4 cancer. So sometimes i dont get to stuff right away. Appreciate the input from yall !

 

With the engine running you should see 13.5 - 14.5 volts at the alternator large B + post

This may not bee seen on other points of the car dependent on cable connections quality

 

Have plenty of charge voltage. 14+

 

MAF sensor voltage checks out good. Fuel injector voltages check out good as well.