HI I HAVE JUST PURCHASED A 1995 JAGUAR XJ6. i LIVE IN NORTHERN CALIF. I HAVE WANTED ONE OF THESE CARS FOR SOME TIME. HAD IT ONLY TWO DAYS AND THE TROUBLE JUST STARTED THE GAUGES JUST STARTED TO GO CRAZY IT WOULD DIE ALL GAUGES WOULD GO TO ZERO AND DIE FOR A COUPLE SECONDS AND GO INTO LIMP MODE JUST BARELY GOING FINALLY GOT IT HOME AND PARKED IN GARAGE. TALKED TO A JAGUAR MECHANIC AND HE SAID FIRST THING IS TO CHANGE CRANKSHAFT POSITION SENSOR AND I DID NOW THE SAME PROBLEM OCCURS BUT GAGES ARE STEADY AND CAR STARTS AND DIES. I HAVE MEASURED THE GAP BETWEEN SENSOR AND IT IS .046. ARE THE SPEC. .018 TO .042 I CHANGED THIS TO .025 AND NO CHANGE. I AM RETIRED AND WORK ON ALL MY CARS AT HOME HAVE AN OBD11 THAT REGISTERS OCCASIONALLY P1775,p1790, P0727.. THANKS IN ADVANCE FOR ANY HELP. EXCITED JIM / HAVE EYE PROBLEM CAN SEE CAPS BETTER. EYE SURGERY AND LENS IMPLANT AND 74 YRS OLD.
HAS NEW 900 CCA BATTERY

I replaced crankshaft sensor with lucas still misfire $107.99 -$20.00 online purchase =87.99 +tax auto zone



checked two temperatre sw 1 pin temp sw water heated on stove
normal temp .65k ohms to .09k to almost boiling

2nd temp with two contacts .
Normal temp 2.75k ohms to.48k ohms almost boiling


Fuel pump pressure at 42 psi constant except when it misfires it drops 5 psi.

I un-pluged the sensor by the throttle body and the engine ran a little smoother and would keep running it has 4 pins. Plug it in and it dies. No measurements on this one till i figure out which one it is. Any ideas or suggestions. What's next. Still misfire isolated alternator. Unplugged iac and misfire still but less but engine will continue to run. Going to ck measurements on iac.
Do you know what measurements should be?
Replaced temp sw. Still misfires. Checking all grounds. Need to check all the front by headlamps. ALL OK.
TPS
I checked tps with it unplugged and key on the
pin 3 was 5.0v
pin 2 was 0v
pin 1 was 0.1v
plugged it back in and
pin 2 is now 4.9v
i saw some where pin 2 unplugged should be 4.9v. Cking all relays and blowing the contact out and putting gel to protect from water and other matter to insure good contact.
__________________
1995 JAGUAR XJ6 X300have about 136,000 mi.

 

Have you replaced the spark plugs?

Cheers
DD

 

P0727 and P1775 can probably be disregarded. My understanding is that they set purely as a *result* of the engine stalling....and do not point to a *cause* of the engine stalling


I could not find P1790 in my X300 manuals. However, it does appear elsewhere as an "Ignition Supply Fault"....which sounds promising in your case. Not sure where to begin on that.......have to do some mulling.


You might wanna check the ECU pins. Quite a few cases of corroded/broken pins have been cropping up

No help on TPS values/measurements, sorry

Cheers
DD

 

replaced with ngk iridium.
no corrosion on cpu pins
will check o2 sensors tomorrow heaters ok on front two 6.0 ohms. SIGNAL wire s/b voltage from .1 to .9v when warm.
ACTUAL VOLTAGE ON SIGNAL 0V-3.5 ON AND OFF EVERY FEW SECONDS EITHER O V OR 3.5V ANALOG VOLTMETER CAN'T READ ON DIGITAL

i'm looking for readings or measurements voltages or resistance on iscv.
any knowledge of those readings.

 

replaced with ngk iridium

 

pins are clean on ecu no shorts or broken pins

 

I would first start with the basics and take a good look at the coils at night with the cover off, should any light up they are bad. Check your fuel pressure at the rail with the ignition on without trying to start the car, make sure your fuel pressure is constant. how did your old spark plugs look? normal, black or white?, if they seemed bone white you have a lean condition and fuel pumps need to be changed. now should all check out I would replace the temp sending unit as this has caused me similar problems in the past,thats the one with two pins, they are pretty inexpensive. now if all is the same hook up the volt ohm meter to the tps, while it is still on the car ignition on engine off, and see how it changes ohms while you gently and slowly open and close the throttle. nice smooth transitions are desirable should it skip over large amounts of numbers or have blank spots it is bad. my 2 cents.

 

put in new spark plugs black running rich. just replaced coils last month no flashes at night these are black epoxy in color not transparent. 42 psi, temp sending 2 prong changed last week.
tps .56v- 4.75v variable as throttle is turned from closed throttle to wot.slowly and readings only vary to the next highest readings .05v on each movements seems smooth no gaps.
it runs real good approx 800 rpm till it warms up 3-5 min and then dies .
i just checked the two front oxygen sensors the heaters have 12 v to both sides of heater and the signal will fluctuate between 0 and 3v on off with an analog voltmeter. with a digital the signal flashes all over the place flickering can't read both ox sensors flicker. shouldnt the heater have 12v on one side and the other ground or is case ground. i just need to check out the iscv. do you have any idea what measurements The tps just one pin for measurement to ground for voltage. it use to just start and die constantly. now it does run smooth for a 3-5 min. o2 sensors were black Charcoal sprayed them off with carb cleaner.
any other ideas? thanks:

 

I think I have figured this thing out. The o2 sensors has +12v
on both sides of the coil that means I have lost ground to at least 2 o2 sensors so the heaters are not working. an old schematic 1986 shows a ground on intake manifold any one know where this is located. no ground, heater do not work. will this cause my problem. got to find where the wires go from o2 sensor connector.

 

I think I have figured this thing out. The o2 sensors has +12v
on both sides of the coil that means I have lost ground to at least 2 o2 sensors so the heaters are not working. an old schematic 1986 shows a ground on intake manifold any one know where this is located. no ground, heater do not work. will this cause my problem. got to find where the wires go from o2 sensor connector.

 

Uh-Oh. New coils. There have been several reported problems with new aftermarket coils causing misfiring and other strange symptoms. Sorry to dig that up, Doug!

The sensor near the throttle body (on top) with 4 wires IS the IAC (Idle Air Control). Unplugged = open = more air though throttle body, probably higher idle RPM. Plug it in and it dies = bad IAC, closing off air supply. Or, very dirty throttle body with IAC passage blocked too much. However, in theory the IAC should compensate for that, by opening more to keep the RPM in range.

 

It runs fine when cold no misfires. Why would coils go bad when they warm up? Could no ground to o2 sensors be causing misfires when engine warms up no heater there to feed back signal to computer and dump more gas into the cylinder causing carbon buildup on plugs and o2 sensors. I just have to find the ground. Probably close to ecu. Working on that right now. Previous post +12v on both sides of o2 sensor heater, means no ground to other side of heater. So heater will not work. That should be my problem. Have to find that ground that is missing. That side feeds back to cpu pin 30 on black connector and pin 8 on red connector. Looking for ground to ecu. Pin id (b) three locations.

 

Have iscv coming fedex slow mail it should be here monday

 

Near as I can tell the oxy sensor heaters are grounded by the ECU, Pin 4 of the Black connector.

It *might* be that the heaters are not intended to be on at all times. If that's the case (and I don't know if it is) then the ECU might apply 12v + to that pin to defeat the heating






Sorry but you're losing me


Cheers
DD

 

That's fairly typical on these cars....coils giving trouble after they absorb lots of engine heat

However, your coils are new

Many of us have had problems with aftermarket coils. But....they usually work fine for a few months at least so you should be OK I think

Cheers
DD

 

it not coil i even wrapped them with elect tape and no difference. i have no ground on o2 sensors. +12 on both sides of heater so coil is floating and +12 passes through coil to other side because it is not grounded . it looks like the signal to o2 sensor is a ground from cpu or ecu. i don't know this CPU but would like to have a copy it. to futher diagnose. I'm going to tear it apart and maybe make my own schematic if i cant find one.

 

Please do one test to satisfy my curiosity. While the car is running disconnect the Air Flow Meter and see if that seems to fix your idle.

 

P 1104-4 my pin 4 on my schematic shows uk label output pin and goes to #4 ign. Coil. My pin 1, 35,36 shows grd.
My schematic says sedan range 1995 aj16.
I am on the board trace circuit to t701 - irf530 looking up what that is and try and see if it is bad.
WILL TRY AFTER I GET ECU BACK TOGETHER

 

Does this iac bring defective will it cause the o2 sensor to have no ground and shut down the heater. If it does then this iac has to be bad. After i get this thing back together i will test again by unplugging iac and then replace iac it should be here tomorrow night unless fedex they loaded it on a ups flight that crashed. Thanks

 

Find a schematic labled "AJ16 NA Federal Engine Management"

I think you're looking at an "ROW"--Rest of World---schematic

Cheers
DD