Today I decided that I am sick of hearing VTC clatter every time I start up the car. But, I don't want to pay Nissan upwards of $700 to fix the problem, so I am going to look into doing all or part of the work myself.
The first step is to determine what exactly the problem is, and where all of the involved components are located. Nissan has been... less than helpfull... with this information, so I am going to turn to some other resources.
Today I went to a local import specialist, and for $5 obtained a copy of Nissan Technical Service Bulletin NTB95-022. This TSB gives detailed instructions on how to rebuild the VTC sprockets, but does not give information about where they are located or how to remove them. It also specifies a procedure to test if the VTC sprockets have gone bad, but I believe you need a Nissan Consult to do the test.
Curiously, the TSB says "Do not replace the VTCs." A Nissan dealer in San Luis Obispo, CA once told me that they would not perform a rebuild, only a replacement. They claimed that Nissan will not warantee a rebuild. But, in the TSB Nissan explicitly says NOT to replace the system. So why did the dealer say I had to?
Unfortunatly, rebuilding the VTC intake camshaft sprockets requires a press capable of exerting 1 ton of force. At the moment, I am planning to remove the sprockets myself and then take them to Nissan to have them rebuilt. This way I will only have to pay labor for them to just fix the sprockets, not for them to remove the intake manifold, the valve covers, etc.
Of course to remove them I need to know where the silly things are first. From the Chiltons Manual for the 1985-1992 Nissan Maxima we know that there is a VTC Solenoid on each bank of cylinders (3-34, Fig. 43). Somehow this solenoid controls the operation of the VTC system. I'm assuming that the VTC assembly is somewhere in the head under the this solenoid, but there is nothing indicated on the diagram, and there is no reference to the VTC in the index.
After flipping through some random pages I happed to come across the procedure to replace the timing chain. In Fig. 146 (3-66) there is a picture of the VTC assembly (so that's what the evil thing looks like). Apparently the VTC assembly is not in the head itself, it is on the front side of the head, behind the upper front cover. It is connected directly to the intake camshaft, and the timing chain loops over some teeth on the assembly (the VTC sprocket).
Look at your engine and locate the VTC solenoid on the front valve cover. If you then look below that, and at the far left side of the head, you will see a round bump in the metal. The VTC assembly is directly under that bump. (Picture coming soon).
Next I will look into how much has to be removed to access the VTC assembly, I hope the chain doesn't have to come off. Also, I will put up a copy of the TSB, and take some pictures so you can see what I am talking about.
