Hi-I have a 1999 XJR with a troubled engine that overheats and consumes water.

Got a used 1999 XJR engine that ran fine before we removed it from the car and then installed the new engine in my car.

No go.

Checking all over and found some diffs in the cat sensors and throttle housing.

Enginenumber check turned out the old engine was a AJ26 while the new is a AJ27, though the cars are booth model year 1999.

Using the original ECU.
Engine almost fires but hesitates and dies.
Are the ECU different for AJ26 vs AJ27?

 

The ECUs are different. You should keep the original ECU and do the following:

1. The intake camshaft (Left Bank) reluctors for the cam sensor are different. Replace the AJ27 reluctor with the one from AJ26. The reluctor is attached to the back of the camshaft, press fit, but it is easy to knock it out.

The AJ27 also has a reluctor (and a cam sensor) on the Right Bank intake camshaft. This is not used by AJ26 ECU so you can leave the reluctor and the sensor in, sensor not connected. If your AJ26 has a blanking plug at this location (back inner corner of the head), you can remove the AJ27 sensor and use the plug from the AJ26 to blank the hole.

2. The Knock Sensors are different. You need to use the original ones. The AJ27 knock sensor sits on a stud; remove the sensor and the stud and screw-in the "can" type sensor from the AJ26.

3. The Throttle Bodies are different - use the AJ26 one.

4. The ignition systems are different - you have to use the original ignition 2-wire coils.

5. The Oxygen Sensors may have different connectors but their functions are probably the same.

 

Thanks ! I will do as You suggest and hopefully report success.

 

Hi, the project is going slow. Having problems sourcing a AJ26 camshaft reluctor. The last advice I got from a mechanic states the reluctor doesnt have to be replaced as its enough to replace the sensor in the head. Is that right? Im in doubt.
Any suggestions ?
Best regards Karl

 

You cannot keep the AJ27 reluctor, it will confuse the AJ26 ECU with its four trigger arms (instead of one in the case of AJ26). The AJ26 & AJ27 cam sensors are the same anyway (may only have different connectors) so using an AJ27 sensor will not solve the issue. What happened to the reluctor on your original AJ26 left intake camshaft? Did you try to knock it out?

 

Many thanks for rapid and detailed answer.
I suspected something like You says.
No, cant knock out the reluctor on the original AJ26, as I stripped all I needed and gave it away...not too smart I guess.
I will keep hunting the AJ26 cam reluctor.
Thank again
Karl

 

The part number is NCA2613CA. Did you try here: https://www.jagbits.com/ssearch.html?query=NCA2613CA. Sometimes, the parts suppliers show some parts as available but, when you order, they later inform you that the part is actually not available. Give it a try and see what happens.

 

Did you swap over the AJ26 flywheel and crankshaft sensor to the AJ27 engine?

Did you swap over the old bolt in style (AJ26) knock sensors instead of using the ”stud through” knock sensors? There is a substantial ohm difference between the 2 styles.

I hope you saved the old throttle body and elbow before discarding the old engine. You could have a big mess on your hands.

 

Very good info.

Karl, if you have not kept the AJ26 flywheel, you will have to buy one. There is just one currently on Ebay - https://www.ebay.com/itm/Jaguar-XJR-...53.m1438.l2649. The AJ26 used flywheel NCA1426CE and the one on AJ27 is NNE1426CA. They have different arrangements of the "windows" that trigger the crank sensor.

 

Thank You for the input.
Have done all those point but the reluctor. And didnt know about the flywheel/crank sensor.
Is the flywheel/cranksensor swap necessary to get the AJ27 running good?

 

You know what? Now that I think about it, I don’t believe the AJ26 crank sensor itself has to be used. Most definitely the AJ26 flywheel has to be used though. There are differences between the 2 flywheels. Even if the engine ran, you’ll have a forever check engine light on and/or restricted performance light on until the AJ26 flywheel is installed. And also the correct knock sensors. Where the current AJ27 “stud through” style knock sensors are at, you can remove those studs and install the “bolt style” knock sensors.

 

The AJ26 CKPS can interchange with the AJ27.

I made an adapter harness to use AJ27 CKPS on AJ26 engines when I worked at the dealer.

 

Years ago I wrote an entire story about a customer putting AJ27 engine in a 1998 XJ8.

The customer told me the engine was replaced but neglected to tell me that the engine was originally AJ27.
He swapped everything EXCEPT the torque converter drive plate and the engine ran like $h!t.

I tried all I could think of to get the CKPS/CMPS relationship fault rectified.

I finally sat down with him to discuss where I was at and he told me about the AJ27 engine in the AJ26 car.

The AHAH moment struck me and I asked if the torque converter drive plate had also been swapped?

He said NO!!!!!!!!!

I told him that they were different and he looked embarrassed.
He brought the AJ26 part and I removed the gearbox to swap it.

Engine ran fine!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

There is a set of camshafts on Ebay with the left intake camshaft coming with a single arm reluctor: https://www.ebay.co.uk/itm/JAGUAR-X3...1&isGTR=1#shId

 

AUGUST 2003 Jaguar Tech Tips info.

Models – XJ/XK AJ26
Information: Please be aware that when ordering replacement heads for a AJ26 engine that the heads have been superseded to AJ27 heads and the tappets will have to be replaced with a AJ27 tappets. This will be necessary to gain proper valve clearance.

There are differences to be aware of when swapping heads/cams.

You only need to swap the 'B' bank intake cam. That is the only one that has the reluctor that matters to the AJ26.

 

The NA cams are different from the cams on SC engines. Karl could buy the four (NA) cams just to get the reluctor which is easy to pull/knock out and just swap it with the 4-arm reluctor he has on the AJ27. A bit high price to pay for the mistake but it is a solution.

 

Hi all,
I had an incredible luck today and have found a AJ26-99 with warped heads for a very reasonable cost. Will take a trip up north and pick it up this weekend.
Thanks for all advice and help.
Will extract the needed parts and transplant them into my car and hopefully make a testdrive before winter hits up here.
Karl

 

The project was put aside due to lack of time.
Meanwhile I have got hold of two bad cams with single-wing reluctor from AJ26 SC.
Now when things are slow I tried to take out the reluctor but no luck.
The first ended up damaged due to excess force during removal attempts(heat/cold/pull etc)
Got one left and will hopefully not ruin that on also.
How is the reluctor assembled to the camshaft? Pressed or heat-cold shrunk like a cogring on a flexplate?
Is it possible to grind off the not used wings on the four wing type, i.e are any of the wings at the correct position?
Karl

 

The reluctor will slide back-and-forth in the slot so it might be a slight 'dovetail' like a firearm sight.

See TSB 303-08

 

I believe it is just press-fit. In any case, I removed one with no major hustle but took time and patience, I either had or specially made a very sharp wedge about 6 mm wide. Then I just placed it at 4 points (one at a time) around the joint cam-reluctor (see pic) and knocked at the wedge with a hammer, little by little, going around the 4 points. Eventually, the reluctor started moving out.