Hi guys and gals, Happy New Year !!!
Alas my beloved Sovereign has once again failed me but gave me 3000 miles of trouble free driving after I replaced the crank sensor. Problem is the car started having the same issue as before. Basically could not push the gas down very far as the car would cut out like there was no fuel but as soon as you let the pedal up it ran fine but only in lower the 2k rpms. The issue gets worse as it gets hotter meaning longer driving time. Also backfires through the intake. 30 minutes generally ok 45 minutes less power. An hour barely makes it back home. On my last trip out made it to Home Depot ok but then when I started it I rolled forward about a foot and it stalled. Cranked but to no avail. Checked for spark. No spark. Jump the ignition with positive direct to coil. No spark. No start. ICM? It's the only part I never replaced. Do you think it would cause the issues before it stalled as well? Also, what are some less expensive ICM alternatives ? I remember a GM one replaces it. Is there part numbers you can share? Is there any benefit to using a high performance one for positive ignition at higher rpms? Accel? What are your thoughts?

 

Hi Pappajag,

Sorry to hear your Jaguar is misbehaving. The first thing I would recommend is that you check the Vehicle Condition Monitor for any stored diagnostic trouble codes. To check, turn the key to Position II (ON) without starting the engine. Depress and release the VCM button on the trip computer panel to the right of the steering wheel, and watch the small display below the speedometer for any message. If something is displayed, write it down exactly and post it here.

Also, please tell us the model year and and engine size of your car. It's helpful if you add that information to your signature line so others don't have to ask.

Cheers,

Don

 

Hey Don B., thanks for the response.My specs should be on my signature below. If not I will have to see what is up with that. But the issue is on my 1991 XJ6 Sovereign 129k miles.

Codes before it stalled were 11,12,26,44

The no spark is brand new. I suspect the ICM. Is that the correct terminology for the part?

Also,I remember reading that there is a GM part that replaces this for a lot less than actually asking for a Jaguar part. Like $200 less? Where would I find that part number?

Fuses are all good. Does the emergency cut off switch control spark? I thought it was fuel only. Also where would it be located on my car?

Any help is greatly appreciated.

Mike

 

Hi Mike,

FF11: Idle Potentiometer not in operating range
FF12: Airflow Sensor not in operating range
FF26: Oxygen Sensor Circuit - lean exhaust / vacuum leak
FF44: Oxygen Sensor Circuit - rich or lean condition

Your poor Jag is not happy!

My first question would be, how low is your battery voltage sagging while cranking the engine? If the voltage falls much below 11V the Engine Control Module (ECM) will not trigger the ignition to fire.

The next things to check for no spark are the distributor cap and rotor button and the integrity of the king lead between the coil and distributor cap. Next you can check for the proper voltages at the coil and ignition amplifier (what you are calling the ICM or ignition control module). With the key in Position II (ON) but the engine not running, you should have 12V on the White wire with Pink tracer line at both the coil and ignition amplifier.

You can download the 1991 XJ Electrical Guide at the link below, courtesy of our member Gus and his website, jagrepair.com:

1991 XJ Electrical Guide

Regarding all the other fault codes you have, low battery voltage or corrosion on battery power connections and grounds could contribute to these issues. After load-testing your battery, the next thing I would do is to clean the ground points used by the ECM - the two on the intake manifold and the one on the firewall behind the cylinder head. See the photo albums at the link in my signature - I have a lot of albums on cleaning the battery power connections and grounds.

I don't think the inertia switch is your problem, but to check it look in the left corner of the driver's footwell behind the carpet. The switch is a black plastic box with a plunger button on top. If that plunger button has popped up, the switch has been triggered. To reset the switch, just press the plunger down.

If you don't have the Haynes XJ40 Repair Manual, you can download the U.K. version at the link below, courtesy of the Jaguar Forums. The file is missing a couple of chapters, but the section that explains the trouble codes is there:

Haynes XJ40 Repair Manual

Please keep us informed.

Cheers,

Don

 

This is what I came up with while check a few weeks back. Hope it helps!

 

Before you go spending any money on parts, try cleaning and tightening the MAF plug connection along with any other sensor connections you can get to easily.

Just a suggestion but often the cause of problems ..

Larry

 

Thanks Larry,ironically when I took the amplifier connection apart water or a liquid came out of the connector. We had some snow that had melted in between me going in the store and coming back out when it stalled and lost spark. I sprayed it out with electrical contact spray cleaner then blew them out with the compressor but to no avail. Did not work but would of that killed the amplifier getting wet while running?

Currently out of time but will try to get to testing the contacts and grounds before I spring for an amplifier.

Do I dare take one out of my 1994 XJS 4.0l that is running well to see if it works or am I risking killing that as well? They have the same engine.

One other issue. Oil was low, like not reading on the stick. I put in enough to get between the fill lines on the stick. Is there a low oil kill switch in the car and if you set it off, would you have to reset it in order to get start back? As always any help is greatly appreciated. I think you guys are the Jaguar Gods!!!

 

There's no low oil kill switch, but typically the oil pressure gauge on the dash will show low oil pressure.

Regarding the water in the ignition amplifier connector, that definitely isn't good. Check the schematic to see which fuse or fuses protect those circuits and then check those fuses. If they're OK, then you can probably safely swap in the amplifier from your other car for a quick test.

Just for the record, instances of failed ignition modules have been rare, and no-spark issues have more frequently been due to low battery voltage while cranking or problems with the distributor cap & rotor or king lead.

One other thing worth checking is the engine ground strap, since it completes the circuit for everything grounded to the engine block, including the spark plugs.

 

I agree but what ever it was happened as I was pulling out of a parking spot suddenly. The car was running and voltage showed 13v plus. It just just off like a switch was flipped off. I have recharged the battery since and no spark at cranking. Coil was replaced just this last summer and it ran fine. We we lose spark if the crank sensor wire was compromised? Water etc...

 

Sorry that should read " Would we lose spark "

 

If the CPS is compromised you will have no spark because the ECM will not know when to trigger the ignition.

Even if the battery is freshly charged, if its voltage sags much below 11V while cranking you will have no spark because the ECM will not trigger the ignition. Jaguars require stronger batteries than most cars.

You can download the AJ6 Engine Management Systems at the link below courtesy of our member Gus and his website, jagrepair.com:

AJ6 4.0L Engine Management System / OBDI Diagnostic Guide

Cheers,

Don