after searching and using some advice found here in the threads, i realize that i am missing something. The answer. Why does this car run so crappy, stuttering idle, restricted performance on display, and after purchasing a code reader/eraser (Autel MS 3000), i have usually around 7 active DTCs, and 5 pending codes.
History: I just purchased the vehicle. 2000 xj8, with 111,110 miles. Previous owner has had vehicle since 2004. He reports that it has never given any issues and with normal maintenance along the way, it has always been a great daily driver for his Dad. After Dads passing, the son continued using vehicle, and driving daily thru 2018. (Not registered since then). during the down time, he reports that with occasionally starting the vehicle, it has really not been used.
Fast forward to this year. He needed to sell vehicle, and it wouldnt start. Dead Battery. Purchased new battery. Interstate Silver series with 850 CCA. Recommended size according to him at over $300. Vehicle started up, and all the codes present themselves.
p 1647,p-102,p-103,po-112,po-353,po-327,po-354,po-1642, and the amber light is constant on dash, with occasional red light also. Check engine light is mostly constant. Using the code reader and attempts to erase, the unit sends a "erase fail" message after wards. But then, a re-scan will show "No codes". hhhmmm..
Previous owner wanted to start replacing all the areas that the codes were showing, but funds $ were not abundant. The gas had also been in the vehicle for at least 6-9 months, but actually ran out while i was contemplating purchase. (I filled the tank with 93 premium on the way home from buying it.) He did however replace the MAF sensor, and the wires leading to this sensor above the Air Filter box appear to have been spliced for some reason.
New sensor did not solve anything. The vehicle has been stored inside garage, out of weather. No Rust on any surfaces of car, and even the rubber seals around windows, tires, wheels and edges of car are clean and free of rust or even mold/mildew . I mention this because we are in Daytona Beach, and florida is notorious for destroying vehicles setting outside in less than a year.
At this point i purchase the car, and drive it home about 40 miles. sluggish and absent of any power, the car drove as expected. Tranny is good and shifts well thru all gears, engine sounds smooth with no weird sounds, pings, or even tapping. No smoke, no smells, and vehicle drove straight and braking was straight and smooth. No temperature spikes, and all fluids are topped to proper amount. Yesterday was first day i have had to look it over and play. No Air Filter present. Battery holding good charge, and alternator charging evidently. No load tests done on either yet. I purchased Air Filter and installed. Checked for any loose wiring, or disconnected items. none found. All items work as intended inside the vehicle. All controls for air and heat, radio, settings, cruise control and trac control work perfectly. Cruise actually worked on the drive from purchasing, even with amber light and check engine light on. Interesting as usually any engine issues, especially Restricted Performance, would have me believe that CC would be first to be disabled.
Ok. Thats the history. Car starts up easily, idles and warms up usually smoothly (a few minutes at most), and then starts stuttering, acting like it will stall. No, i am not currently trying to drive this vehicle before returning it to good health.
Sorry if this is too long, but hopefully the info i put in will spark some ideas, and I really have no further info except what is listed. The condition of this XJ8 is impressive, and well preserved.
All ideas are helpful, and I will monitor and report any changes. Yes, I could take this to a Jag mechanic/dealer, but what fun would that be??

 

The wire splice on the MAF is critical that it be soldiered and not a butt splice or corroded inside the splice

While you have the wire apart you can test the output from the MAF to the ECU on the Green / White color wire

At the proper idle speed the reading should be 1.2 volts DC

This can be seen on page 102 and page 46 pin EM83 - 28

jagrepair.com/images/AutoRepairPhotos/jagxj2000.pdf

Your spot of stumble under the bonnet , does it accure as the coolant temp cross 88 degree C when the ECU goes into closed loop mode starting to use the O2 sensors for full engine regulation ?

Your codes are here

AJ27_ECM_2000.pdf (jagrepair.com)

Your engine manual is here for the AJ27 engine

T881 TITLE (jagrepair.com)

 

Parker7 i am concerned quite a bit about the offhanded way that the MAF was spliced in, as you pointed out. I also need to make sure he even hooked the correct wires together. What i dont understand is Why they became spliced. Just to change out the MAF would not have dictacted cutting the wires, would it? stumped.
The stumble and loss of idle consistency during warm up does not really wait on temperatures to rise. Sometimes it will be with half a minute and it starts to rumble and jerk. Another time it might be a couple minutes. No consistency from cold start to it beginning to exhibit the symptoms.
I cant thank you enough for the links to those manuals and details of which i will take advantage. I have looked up the codes and they are consistent with what you just linked to me. Would it be normal for knock sensors, both, to crap out at same time as MAF, and O2's and HO2's ? Or, is there one common denominator that is setting the dominoes in motion and showing the fails?
I will be dragging out the multi meters to measure the voltages now. Weather is not cooperating with shade tree mechanic antics ..

 

The knock sensors if triggered will retard the ignition timing on that cylinder or all , someone would know more then myself

You can have a faulty knock sensor giving you a un needed retarding

There seems to be alot of talk on these sensors on this engine

Can you just unplug the knock sensors and get a test run ? Someone would know more

 

A failed KS will retard ignition on ALL cylinders.

When any KS DTC is logged..................................

When DTC is logged (first trip), ECM:
– Sets ignition retard to maximum
– Limits engine speed to
3000 rpm

 

Am I justified in having these replaced without knowing what caused both banks to send a code, along with coil packs A and B showing code also? Did the lack of being driven for a few years do this? Did the battery replacement play a part? I am too new to Jaguar to know if these things happen when these cars are not used. Motorcycles and RV’s will be affected badly by non use. Should I trust all the DTC codes and start throwing new parts on? The car is worth much more than I have in it, but wasting $ is never a wise idea, right?

 

You might check for RODENT DAMAGE if the car sat for a while.
Rodents chew wires and hoses so you might be in for some surprises where they like to nest?

 

Because the codes that are continuously evident are showing both of the knock sensors have a fault the research I am doing on these knock sensors for anybody’s further reference is they are very temperamental and sensitive to a certain frequency that is tune directly to the engine and the pistons and the combustion. There are a few different ways to test these knock sensors however having a new knock sensor handy when you were doing the test so you can replace the bad one will be the best course of action. I am seeing the possibility of a bad ground where the knock sensor is screwed into the block or the head and this could be an issue if you do not have continuity but normally knock sensors are going to show Krazy values and drop in voltage that is more than 2.5. I’ve also received and read that OEM is the way to go and not a aftermarket replacement.saving a few dollars is just not warranted here.

 

this should be a vid link for location and testing.

 

So, I have replaced all 8 ignition coil packs, and spark plugs. Two new strut brackets for front , new air filter, and have load tested battery for any failures or bad cells. Results : car now runs extremely smooth, with fluid like acceleration and no more banging with new strut mounts/dampeners. However at idle, it jerks and the tach is not steady( 620-750) rpm’s. No more misfire codes, or coil codes.(had two). MAF is showing -40 c IAT. Never changes. Still shows the knock sensor code, too. Restricted Performance on display still. Check engine light will go off when codes erased, but comes right back at new engine start. Any ideas how to bypass that knock sensor ? Tearing down the top of motor/intake manifold, does not sound fun. Thanks to all that are following this.

 

Could be a bad spot at idle on the TPS sensor going in and out of expected range and the ECU using a default set of not optimal maps and restricted performance

There is a time delay in this happening and going back to normal , so it doesn't happen at the precise moment it loses a TPS signal out of range

To test the TPS it should be 0.50 volts DC at the idle stop with the connector installed and engine not running but the key to the run position

They should be a smooth increase in voltage as you slowly slowly twist the throttle open and never a bip to zero volts

There are 2 TPSs one for the engine and one for the transmission ECU

Your wire color is X for engine and Y for transmission

There is a history of the transmission connector on the transmission itself getting contaminated and effecting the transmission ECU ( transmission speed sensors ) which cross talks with the engine ECU as they dance together in coordination

This usually from reading acures in the idle range

See page 101 lower right side for the engine and 108 top for the transmission ( non - MB transmission for the supercharged engine )

The TPS wires can be cross referenced on page 45 as pin EMB1 - 10 and EMB1-- 19

Notice that one is at 0.50 and the other is 0.60 for some reason

X300 00/E COVER (jagrepair.com)

Injector cleaner in the tank ? may have a dragging injector

 

Assuming code reader reads values correctly, then that -40'c all the time from IAT is broken sensor in the maf or just broken wire. This should be remedied first.

 

Adding to what Vauxi said, it’s also possible that the MAF wires inside the connector may have backed out enough to not make contact with sensor pins. While the MAF is plugged in, you can take a small flathead screwdriver and gently push them in towards the sensor just to make sure they’re firmly sat in place and see if the -40*C goes towards ambient (assuming you haven’t ran the engine at this point) temperature.

On a naturally aspirated engine, the knock sensors are easy to replace with the right tools. You don’t need to remove the intake manifold at all. You have to remove the cover over the fuel injectors. In between the 2 middle injectors is an opening that goes down and you can see a nut and a stud. Remove the nut (use a magnet for the nut), use a small curved pick to lift the knock sensor up over the stud. You’ll need to fish the new wire through using the curved pick or some hemostats.

 

You do NOT need to remove the intake manifold of a Normally Aspirated AJV8 to replace the KS.

They are visible through the plastic intake runners and can be accessed.

The early (AJ26) KS have a bolt fastening them to the block and a STUD for the later (AJ27) engines.

Remove the nut and then remove the stud with a special socket. (reverse TORX)

The socket is E something or other (can't remember the number) but a cheap set of E sockets don't cost much.

Fish the KS out from under the intake and 'fish' a new one under and into place.
Maneuver the stud into place and install nut. (DONE)

 

Thanks to motorcarman and all the rest! Knock sensor will be replaced along with checking those wires to MAF plug in and might as well replace that sensor. I’m not exasperated, just running down the to-do list. New tires and complete tint done today(sitting in tint shop waiting for completion now). Making this the nice car that it is begging to be, and each of the mechanical items I have done, have done wonders. Cause of all this? I believe sitting for years(4 or more) with little or no use, and completely ignoring the maintenance items that did pop up. Thankfully, it is worth it. Btw, one of coil packs had actually been JB welded on one side previously! Amazing.

 

Rock Auto has the KS for cheap.
Used to be AIRTEX but the boxes changed.

I keep them in stock for the 3 X308 sedans I drive.
WVE 5S5622 {#LNE1692AA, SU7015}

 

you were right about the replacement of the KS. The code showed which was bad, and I replaced. The wire insulator was cracked and probably a wire also. I didn’t look. I cleaned up the area and put new one on. (Todays price was $90)Also installed new MAF.
So the good news is no more KS codes, as I figured this was the cause for the restricted performance display on dash. Nope . It’s still there .
I will now go back to the patch job on the wiring to the MAF harness. I don’t trust it, and not sure if he just twisted wires or not. Or if the right colors were hooked to right pins. With all the other codes that needed attention, I have it down to 3. Po103, PO 112, and P1647.
Engine will not idle smoothly, and when placed in gear, will stall. Restricted performance is still being displayed and now I have an engine coolant leak somewhere by the firewall/passengers side that came our of nowhere. Saw a drip or two, and now as soon as engine begins running, it comes out.
Sorry for not responding sooner. I work and have limited time to tackle all these codes and parts replacing but I am so appreciative of the great responses by all of you. Now the weather is being fickle.

 

knock sensor replaced and thank you for the advice on the magnet. Worked easily and no issues.
The MAF is next. I think it’s wired up all wrong, or at least 2wires are connected wrong. (IAT is still not responding and the graph has no temp) new MAF was installed and no change so wires next. Po112,po103, and p1647 are remaining codes. I will post progress and updates as I tackle them. Thanks!

 

The IAT sensor can be tested with a 9 volt battery powered meter and at standard temp of 25 C should be around 2000 ohms

It is a solid state thermistor so it only measures in one direction

The red meter lead must be on the X color wire on the opposite side of the connector ( the sensor )

The MAF wires will have one ground wire , Black / White wire

A supply voltage wire , White / Blue wire , B+ volts

and the ECU return , Green / White wire

 

See page 129

http://jagrepair.com/images/Training...ual-9-5-01.pdf