Can a VVT-i problem sound like an engine knock?

I've been trying to diagnose an engine knock problem for months now.

When it first started, I switched from Costco 87 to Costco 93 fuel. It seemed to go away.

Now, it's back, but I'm still running 93.

It seems to happen right before the shift points.

I had a tuner examine my log file, he saw no evidence of detonation.

The local Toyota tech told me it could be the VVT-i system and that he deals with such all the time.

How would I go about diagnosing this?

I know nothing about VVT-i.

Thanks.

 

There are two vvti solonoids that could possibly have failed and also two vvti oil filters that I've read can be removed and cleaned/replaced depending on conditions.

Use the search and there is probably some good info out there but I believe those are the likely places for the system to fault.

 

Normally any noise related to the timing chain or variable valve timing system is going to be a sharp rattle/knock at startup or a rattling at idle because oil pressure is low and the system relies on oil pressure to keep the chains tight and the phasers in time, also generally when there is a timing or VVT related problem there will be timing related codes set.

Noises are very difficult to diagnose without hearing them in person, the 4.0L is an inherently noisy engine to begin with so it's often difficult to determine if a noise is normal or not.

 

Yes it can. Low oil pressure in the phasers, for whatever reason, will make them "knock", under certain conditions. It is fairly rapid noise, but a throttle blip can sometimes get it to stop.

 

Thanks for the info. Assuming full, clean oil, what would cause low oil pressure in the phasers?

 

Clogged VVT screens, or a gunked up engine. No clue the cleanliness of your engine.

One member had a clogged port going to that area. Kept getting cam codes and poor operation. Don't remember if there was knocking or not. He ended up using some piano wire to clean out the gunk, which was not visible until the wire was pulled back out. Then it ran just fine. Just something to share.

 

VVTi typically only makes noise on start up. It rarely is continuous, but it can happen.

 

I would also look at the VVT screens. Passenger side is easy, driver's side requires loosening and setting aside the alternator. Still, an easy job.

 

Apologies. I should have clarified the VVT screen above^^^ . Not filter.

 

It's all good, brother. I thought that might be what you were referring to, but figured I'd throw out a little clarification. On that note, I would not recommend that OP try to clean those little screens. They're dirt cheap at the dealer, so just replace them. Amazon carries them too.

 

Been needing to replace mine for a while. Just ordered them.

 

Look here for what and where OP
https://www.tacomaworld.com/threads/vvt-replacement.685602/

 

The link in that thread is mine - I forgot about that one.

I quit posting in it after several people said it's impossible for those to get dirty or clog - despite the pics I posted. No use arguing.

 

Yeah. I agree that they can get clogged.

I never had mine out. Do they seal with an O-ring?

 

The bolt you take out has an o-ring on it, that's how it seals to the head. It also has a little nub that the screen pushes into. So you push the screen on the bolt, and then insert it into the head and tighten it. Just have some tweezers on hand when you do the job, because when you undo the bolt the screen can stay in the head. Tweezers work great to remove it.

 

Filters/screens don't clog. That's not their purpose.

 

I replaced one of mine that I accidentally broke. Started and drove with no power going to it but never had any noises as a result.

 

So you’re saying we should do like John Deere. Just leave the filter out?

Seriously, our X500 has a place for a cartridge filter. But there isn’t one in there.

 

Change your oil on time and use a good quality oil and there should be no reason for anything to clog or be dirty.