Had a loud rapping noise coming off of idle and changed the secondary tensioner, the existing one was a third generation, but there was enormous slack in the chain so we changed the chain and the tensioner but ended with the same rattling noise.

Decided to disconnect the passenger side VVT solenoid and the rattle went away.

Is it safe to run it with both VVT disconnected until I can take it to a pro?

I think I read in another a thread that I may be able to go up a weight in oil or add a restore or STP type product and the noise will go away?

Any thoughts?

 

This is copied from a previous forum post:

There is a Variable Valve Timing unit on the front of each bank of cylinders.

On the original V8 (named AJ26) the VVT was simply a digital operation that switched between fully advanced or normal.

On the ’98 onwards engine (AJ27) the VVT has a 10 degree greater operating range and works in a linear fashion: i.e. any angle of advance between nil and maximum. It is also significantly physically diferent with the VVT solenoid embedded in the engine rather than being bolted on externally.

Both types use an electrical signal from the ECU to open an electro magnetic valve (one for each intake cam shaft) that allows oil pressure to exert an influence on the advance mechanism located between sprocket and cam shaft.

The fact that your problem exists at idle suggests that there is too little oil pressure to operate properly.

Assuming that there is adequate engine oil…..

The obvious question is; does your oil pressure decay at idle?

If feasible I’d be tempted to swap solenoids to confirm which part is at fault before committing money to buying replacement parts.

On AJ26 the solenoid can be removed in about 10 minutes by undoing two screws and one connector. They’re interchangeable side-to-side which helps…

On the AJ27, it’s a different story: the front cover of the engine has to be removed to access the parts so it does involve considerable work.


There is an explanation of the VVT operation in a Jaguar Technical Guide - "aj-v8 engine and 5hp24 transmission" here http://matt.zenfolio.com/ajv8-engine...ansmission.pdf

 

Yes, a can of 'Restore' is a simple, cheap test to determine if the noise is an oil pressure issue. Certainly will not hurt anything, cost less than $10 and can be reversed by an oil change.

 

Is it going to hurt anything or cause a check engine light to run it with both VVT solenoid"s disconnected?

I was working with Tom and as he stated in his first post we changed the passenger bank secondary tensioner because of excessive slack in the chain between the intake and exhaust cams. the replacement tensioner and replacement chain resolved the excessive chain tension.

It was after this that we still had the original noise and decided to disconnect the electrical connectors from the VVT solenoid's and that is when we discovered that the noise went away with the passenger (R/H) side disconnected.

I understand the concept of the VVT as a way to level out the power band throughout the RPM range but is the ecm smart enough to know it's disconnected and throw a check engine code?

My thought is to drive the car after adding a can of $10.00 magic for 20 miles or so to let it mix with the existing oil (which by the way we noticed is at the low mark on the Dip Stick after we buttoned everything back up and disconnected the VVT) Then after the oil has had a chance to mix with the Magic in a can re-connect the VVT solenoids and see what sounds we get

Barry

 

I believe those VVT solenoids et al require a good FLOW of oil to keep them quiet and operating properly. I wouldn't use anything that increases viscosity. It's normal to get a little "knock" at startup if you hit the gas before they have had a chance to "oil up". If it keeps coming back -- especially while drivng -- you have a problem.

Make sure your oil level is correct. That may not be by the stick as some have noted.