Hey all, At the moment I have Niall looking at my 300 to try and find out what is wrong with my car (why she misfires and it also is down on power compared to similar setups). Currently, we believe that the problem is mechanical and we're looking at the VCT on the car. Niall believes there is a problem with the Valve timing somewhere as he did a test using a vacuum gauge on both cylinder banks with the balance tube blocked (as to seperate the 2 banks) and found the drivers bank has strong vacuum where as the passengers vacuum is low. Has anyone had any issues with their VCT gears or valve timing before and what did you have to do to fix it? Does it sound like we're on the right track? I'm sure Niall will drop in and explain things. Thanks, Marc.
Another possibility is your out a tooth on the intake cam gear on that bank. Disable both VTC solonoids and do the test again. If they're now not equal than VTC isn't your problem. (unless somehow you've got it jammed "on")
Same problem I had. Found the problem was the drivers side VCT. Nissan had reinstalled the sprocket without lining up the locating pin properly. Check out my thread here: http://www.aus300zx.com/forum/showthread.php?t=290891 Pics:
I'd also be checking the VVT locating pin on the front of the cam, JetPower had that problem on his. Edit, Bob beat me by one minute!
You gotta be quicker than that Chrispy. You need any HR advice yet? "How to get that job training" maybe.
the motor has been rebuilt, only 6 months ago by me, so i know the timing is correct and the locating pin is in place. the idle issue was present before and after the rebuild so im looking at something that has remained constant. its highly unlikely that the timing belt was out a tooth before the rebuild, then ive put it together and fitted out out one tooth again.
i dont belive its on the switching side, i think the one of the units has possibly stuck in the on position or halfway on maybe.
Highly unlikely...but we all have our moments The mark could be a tooth out, again unlikely. Have you actuated the VTC solenoids with the engine off to see if it can switch? Oh and make sure you don't have a rag or a mouse or something stuck in the balance tube...that will cause your idle problems. Otherwise things like overpumped lifters and soft valve springs can cause a similar issues, although I haven't come across them in the VG.
my freeware conzult cant actuate the units, ive driven the car with the vct unplugged and it makes no difference to performance.
It is a pain to check, but the VTC check valves can be removed from the rear of the intake cams, it is possible one of them is bleeding and allowing that cam gear to actuate. Here si what I would do in this order. Check voltage drops between engine, ecu, chassis, battery, ptu, coils Leak down test cylinders Check balance tube for blockages Count the number of teeth between timing marks Remove plenum Check both upper and lower plenums with a straight edge Remove intake cam covers Remove intake cams Check valve heights Check intake cam check valves Check VTC solenoids I will be over your side of town on sunday, if you like I can plug in my consult and do a few tests, I have the full version.
Its up to Marc where he goes from here, i really just wanted to diagnose it at this stage. the vac test has shown it is a mechanical problem and not an electrical issue.
Ummm..... this might be fairly easily explained by badly synched TB butterflys that the balance tube is masking. Does the motor run unevenly with the balance tube blocked? Like sorta "thumping" or "thudding" as if the spark was missing a bit on one complete bank? Kinda hard to explain in text but a "brrr brrr brrrr brrrr brrr brrrr brrrr" rather than a nice even note. You can also hear this by listening to the exhaust carefully from side to side (presuming you have twins) The engine would also be a bit slower to come back to idle as well with the tube blocked. L8tr E
