Folks, probably not a common procedure, but I'm hoping to gain your input on the logic.

Task: Swapping a '98 Euro XJ8 3.2 (non-variable valve timing to Euro 4.0 (VVT).

Question: How do I determine which ECU variety to use? Is a set of matching key mandatory? Is reprogramming mandatory? Does reprogramming require dealer service?

Symptom: car won't fire up with the 4.0 ECU that came with the donor 4.0 engine. It will, however, with the original 3.2 ECU, but not very smoothly, and have starting issues. I'm sure the mapping is different.

Thanks guys, I'm sure someone can clarify the logic within.

 

When I carried out this job from 3.2 - 4.0 it was in AJ27 spec, so it could be a different story with the earlier 26.

Firstly have you any codes?
and, have you still got the VVT units in place? if so I'm sure this is your running issue.

I removed the VVT and replaced the timing covers with the original 3.2's - obviously its the timing cover on the 26. I also exchanged the 3.2 cam flywheels, along with tapping the VVT oil gallery and sealed with copper washer and bolt.
If you carried out these tasks then I would suggest replacing the original ECU and carry out a hard reset.

 

Thank you, Sean!

Codes, do you mean fault codes? non-so-far after the swap. Are you saying by doing this swap there's no way to fully enjoy the added VVT on the 4.0? I thought to pair the 4.0 motor with a 4.0 ECU should bring out its full functionality?
And about the hard reset, will that make the ECU relearn its current task to manage? Are these units so smart already?

Again, thanks for the experience sharing!

Paul

 

The VVT actually even costs power. Iirc it is only used for Emission reasons.

 

I guess you've read my comments on the matter.

@Paul, there's a real added gain in performance without the VVT, coupled with the 3.2 diff it's a whole different car than a standard 4L.

Also, the 3.2 hasn't got the wiring to plug into the VVT solenoids, which means they're locked over in fully advanced or retarded, I forget which, but this could explain the rough running. If you where to change all the wiring harnesses from the dash to engine you could have them running but that is a very big job, a route I didn't take because the car didn't need VVT.
Ask Stu1986 about the conversion as it was one of his cars' we modified.

 

An additional area for the VVT is the ECU. You have discovered the ECU for the 4.0 want work. The problem with the ECU is it can not communicate with the CAN the network that allows modules to pass on info. Since you can't run a 4.0 ECU you will never be able to get the VVT to work.

 

@Sean

I think I did yeah... The VVT also causes a lot more strain on the chains as I have been informed.

I always windered why the 3.2l never needed the VVT and managed tonachieve the Euro 2/Euro 3 emissions classes with ease where as the 4.0l not only needed VVT but also EGR...