VVTI Cam Gear position may be off? - Lexus IS Forum
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post #1 of 6 (permalink) Old 06-04-2019, 06:08 PM Thread Starter
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VVTI Cam Gear position may be off?

Long time reader and first time poster on the IS forum. I want to start off by saying I have been doing my own work on Toyotas, Lexus and BMWs since the late 90s but this is my first IS, a 2001 automatic. I recently did a full timing belt job including VCGs but can't remember if I fully set the VVTI cam gear 30deg clockwise after doing the cam seals. My question is if the VVTI gear is not fully 30deg over would that affect the amount of oil that it receives and therefore cause engine knock? My symptoms are that I get slight knocking on hard acceration, but not all the time, no code either (by knocking mean marbles in a can or like a sloppy manual clutch chatter, but not pinging or ticking). Other than the knock/chatter everything else runs like a champ sometimes I think it stalled at a red light its so quiet.

Any input would greatly be appreciated before I tear it down to get a the PITA knock sensors
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post #2 of 6 (permalink) Old 06-04-2019, 09:57 PM
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Originally Posted by Patiolamp View Post
LMy question is if the VVTI gear is not fully 30deg over would that affect the amount of oil that it receives and therefore cause engine knock?

My symptoms are that I get slight knocking on hard acceration, but not all the time, no code either (by knocking mean marbles in a can or like a sloppy manual clutch chatter, but not pinging or ticking).
I'm slightly confused. You refer to "knocking", but then later say NOT "pinging" - but it sounds like your describing engine knock as in detonation/pinging...???

I've recently done timing belt jobs on both my IS300s, and was not aware of the "clocking the VVTi cam pulley 30*" thing. So I didn't. Both my cars run correctly. So I'm doubting that is your issue.

How many tanks of fuel have you run thru the car since the service? My stock car knocks (detonation/pinging) like a bitch on heavy throttle tip-in unless I put 93 octane into it. Always has. Even with 93, I'll hear a ping every once in a while. On 91, it's worse. I've tried 87 just to see - and it knocks pretty good every time I get into the throttle.

My point is - perhaps you've gotten a poor load of fuel? Maybe try another station?
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post #3 of 6 (permalink) Old 06-05-2019, 10:19 AM Thread Starter
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My apologies, when I think pinging I think clicking and higher pitched sounds but both knock and ping are much the same I suppose. The sound i intermittently get is like marbles in a can on hard acceleration just for a few seconds and can't repeat it on demand (like bad ball joint popping turning every time into a driveway). On the VVTI gear I pulled the "allen" bolt and assembly off to do the oil seal and after reassembly I noticed play in the gear before it turned the cam (I had the VCs off). From what I gather, but could be grossly mistaken, the VVTI valve hydraulically fills the compartment in the VVTI gear depending on engine demand for cam oil distribution similar to a BMW vanos system. My thoughts where if I didn't position the gear properly than I may be starving oil distribution to produce the sound.

I am now on maybe the 5th tank of gas and usually put in 87 and drive it hard. When I first got the car it was neglected driven by a retired couple, leaking oil from the top end and leaking antifreeze from the o-ring from the WP to block connection which prompted in a basic top end and TB refurb.

**RE-EDIT** Correction, I can make the sound on demand, when I am driving and mash the pedal I get a quick low octave clickity clack kind of slack being taken up before power is produced. And when I do get gas I get it from where ever it is convenient, next time I fill I'll opt for the high test and see if there is a difference and report back.

Last edited by Patiolamp; 06-05-2019 at 10:42 AM.
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post #4 of 6 (permalink) Old 06-05-2019, 10:49 AM
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The free-play in the cam gear (the outer toothed ring rotates in relation to the center hub) is normal. Yes, oil fills it and a solenoid valve controls the oil fill, which controls the actual position of cam gear in relation to the hub.

As long as all your marks lined up properly when you pulled the tensioner pin, you're fine.

The sound you're describing is "engine knock", otherwise known as pinging or detonation. Have you noticed our cars say "premium fuel only" inside the gas door and in the user manual? That's because the combination of compression ratio and spark timing is aggressive.

These cars will give off 5-10 good audible knocks/pings when you get into the throttle, every time, when you run 87. That is your problem. Put higher octane fuel in it, or continue to get the knock (and potentially damage the engine).
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post #5 of 6 (permalink) Old 06-05-2019, 10:52 AM
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You should google/wiki "engine knock" or "engine detonation" to learn a little bit about what's actually happening inside your engine when you hear that clickety-clackety-knickity-knockity sound you've been hearing every time you mash the throttle.

It's not good.
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post #6 of 6 (permalink) Old 06-05-2019, 12:32 PM Thread Starter
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Thank you for taking the time to reply. This is my 5th Lexus, albeit the first L6 and I have always used 87 with no problem until now. I will check the marks tomorrow when I swap my tires and adjust the coilovers to assure the belt didn't jump a tooth aswell. I also considered that this could be related to carbon build-up in the piston chamber, so badly that it has restricted the volume therefore compressing quicker and detonating sooner whilst the car compensates afterwards. I will dump a can of BG 44K or the like in the tank to help boost the octane and maybe clean a bit of the suspected build-up until the next fill up (I know its snake oil but I like to start with cheap easy fixes first)

Yeah... when you mentioned about ping/knock I did a few searches to help educate myself, I had an old Ford truck that would rattle rock and roll when I turned it off which sounded similar to the sound I hear now.
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