| I have been having detonation issues for a while- among other things I discovered the local Nissan dealer installed the wrong plugs (PFR5G-11). Put in the right "cold" ones (PFR6B-11B) but that did not solve the detonation problems. So I got to figure it must be the air leaks- when using partial throttle (system under vacuum) then I would be getting unmetered air into the engine, ergo it would be too lean. Next thing you know, detonation. At least that is what I am presuming- timing is right, plugs are right, fuel is beyond min. octane. I knew I had some serious boost leaks, I got the boost leak tester (with the pressure gauge and the Schrader valve) and was unable to get it to pressurize. Literally the air leaks out as fast as I pump it in. My mechanic smoke-tested, claims he could not find any leaks. I knew this was bs, so I took it to another shop. They (after 15 minutes of pumping smoke) found a leak from the vent hole on the LH recirc valve. A lot more smoke was coming from the area that could be explained by a 1.5 mm breather hole, but we could not see any other source. I decided to go over my vacuum lines very carefully, found a leak in the hose to the LH recirc valve (so not just a leak in the valve, but a leak in the vacuum hose to it), and also could not hold vacuum to the charcoal canister. I was hoping it was just the hose, but no- the actuator in the canister is shot. That would explain the copious smoke eminating from the LH recirc valve area! I have a new canister on order (I can do ONE thing good for the environment) and in the meantime I have capped off the vacuum and the 2 purge lines. Left the fuel tank vent line hooked up. I had been driving for a while with a faulty detonation sensor (code 34) and wondered if I had carbon buildup from running rich and with retarded timing over a long period (the sensor and both oxygen sensors were replaced August 2013) so I had the Motorvac treatment done recently. Have not tried to leak test since I installed the replacement recirc valve and capped off the canister, but my vacuum gauge is showing an improvement in engine vacuum from 16 to 17.5 inches (altitude here is 3,300 feet, so add 3 to that number- equivalent to 20.5 inches at sea level). Also spent 1/2 an hour this morning spraying starter fluid all around the engine bay, no apparent effect. Problem as we all know is that the Z has a lot of hidden plumbing. Anyone else got any ideas? Take it back to the shop that did my smoke test and have them try again? I mostly would like to eliminate the constant safety boost caused by the detonation issues. It is a little disconcerting. I have not taken it out and tried to replicate the conditions (partial throttle, high 4th gear uphill on the freeway) where I experience detonation since the Motorvac and fixing these 2 leaks. I am keeping my fingers crossed on that. This seems more like a rant than a technical post, I suppose it's a bit of both. I had never heard of the vacuum actuator on a charcoal canister failing before, and I have done a lot of googling about it. So maybe that is a one in a million occurrence, but might help someone trying to figure out air leaks. If this latest round doesn't solve the detonation, can anyone recommend a good Turbo Z mechanic in either- Boise ID, Salt Lake, Seattle, Portland- anywhere within a 400 mile range of Missoula, MT? I have no fear of driving the car that far, just no full boost and baby the throttle. Thanks, Mark
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