Intriguing Noise From 1ZZ

[ThisWill1992]

Afternoon all,

Have been mooching around these forums for some time now, eventually took the plunge and picked up a lovely 2006 MR2 last month. Very pleased with it and finally getting around to making a post! Albeit with a problem 

I have a confusing case on my hands with the engine. It's a 2006 car, 60k on the clock. From the left side of the engine (1ZZ) near enough the oil cap the car starts to tap or knock on idle - but only once warmed up. The noise disappears with revs and comes back, usually within 10 seconds of idle.

I know videos are not the best thing for diagnosing knocks etc, but this is really quite prominent in the video especially with headphones. Here it is idling, roughly half way through the noise develops:

https://youtu.be/fENJO8Zg22s

Second video, after a rev of the engine, the noise is still there and then half way through this video, the frequency of the noise doubles with no change to the engine speed:

https://youtu.be/ljkyOJg0D8g

I have done a lot of research trying to find ANYTHING that closely resembles this noise for a couple of weeks, and I can find nothing.

I will repeat that this ONLY happens once the engine is up to temperature. Oil is new, clean and stable at the right level. Coolant is not leaking out anywhere either.

I can go back to the dealer but it's a 50 minute drive and I'm not sure if I should be driving it or not and they are not being helpful about collecting it or allowing me to take to a more local garage.

Have run the OBD reader multiple times, no codes ever appear.

I've been thinking valve clearances, rods, gaskets, injectors, timing chain, something in the fuel/air mix system - but nothing seems to exactly match what I have going on either by noise, symptom or location of noise.

If anyone can shed any light on this I would really appreciate it. I fully appreciate this is likely to need a proper examination but if I could at least localise it down to something. I'm hoping someone has experienced this exact thing before and got to the bottom of it!

Thanks everyone! 

[Carolyn]

Hi and welcome to the club.  New faces are always good.

Tracking down noises in the engine is not easy.

I would suggest getting a stethoscope (very inexpensive on you favourite auction site).

At the most, the stethoscope might pin down whether the noise coming from the top, the middle, or the bottom.

After that, it's a matter of inspecting stuff. 

The only thing that would get noisy at the top is a valve clearance.

Good luck.

[ThisWill1992]

Thanks for the reply and the welcome!

The noise is definitely top-end, from left-most cylinder area.

My intrigue more stems from the fact there's no noise at cold at all, and it only occurs when engine is up to temp (dial is in the middle). Is there any good reason why this would be? And that there are 0 other symptoms whatsoever.

But let's say for arguments sake it is valve clearance - what is the urgency in which I need to resolve this? That is to say, can I use it if I need to without much worry, or should I leave it in the driveway until further notice?

Any insight much appreciated. Thank you!

[Carolyn]

I can only summise that the oil is more viscous when cold and is absorbing the shock.  When it gets up to temp the oil is much thinner.

Valve noise is endemic on these engines and they will run quite happily with silly amounts of valve clatter. 

I keep the club 'bucket bank' which has a wide variety of thickness of valve buckets, if you want to re-set the valve gaps to OEM spec.

I say buckets rather than shims.  The cams have to come out do do the job.  Sounds daunting, but it's very do-able.  There's a thread in the 'How to' section of the forum.

[Dev]

This is a very odd one. If it was on the timing chain side there are plenty of things it could be but its on the opposite side.

It is also odd that its doing double time like that when the engine is at idle. 

The only thing I can think of is a vacuum valve leak of some sort. This could be coming from the PCV valve, VSV valve or something in the emissions canister being transmitted.   
I would first disconnect and plug the PCV valve hose. Start the car and see what happens. Next I would disconnect the 3 main vacuum lines that are located between the battery and throttle body. You will see three hard lines connected to the rubber lines. Plug them up so you don't lose vacuum and start the car. See if the sound goes away.
 This is just a easy diagnostic step to rule out.

 I would then take it to a qualified mechanic for diagnosis.  Good luck.

[Ozzy]

I think it might be a failing coilpack as it's intermittent but could also possibly be a fouled or loose sparkplug that hasn't been tighted properly. They would make the same noise and would make sense if the dealer gave it a quick service before selling.



I say that as I recently had the same happen with three of my cars (What are the chances lol). Two of them were a MR2 and a 2zz Celica which made the same noise, and in all cases it was sparkplug and a coilpack related. Was either fouled or loose sparkplugs or a failing coilpack. The third car did it once warm as described and was a failing coilpack also and had loads of carbon deposit when checked and ended up ruining the sparkplug.

[ThisWill1992]

Thanks for the answers guys!

I guess I'm hoping that anything valve related would be worst case scenario, although obviously can't rule it out.

In person it definitely sounds "airy" if that makes sense - almost like bubbles, or two softer materials (like rubber?) knocking against each other. I did locate one of the vacuum hoses - didn't realise there were 3 - and plugged it to see if it changed. It didn't - but it could still be coming from elsewhere on the line or a different line.

Definitely interesting on the coil pack / spark plug as I would have thought there would be more out there (videos, guides etc.) that such a thing would cause that kind of noise. However, if you're saying it's happened on 3 different ZZ engines then it had to be worth a go! Exactly what I was hoping for - that someone else had experienced the same thing!

When I get a chance to get in there I'll send in an update. Really appreciate the help so far, thank you!

[Ardent]

Hello and welcome.

Help is our specialty.
Have a look in the events section.
Pop down to  late summer meet and get a hands/ears on full fat diagnosis.

[Frank Rabbets]

Sounds like a plastic plumbing noise.

[ThisWill1992]

Hi everyone, thanks again for your help. I was going to post an update earlier but I was pinged and couldn't get out and about.

First of all, I cleaned the MAF, reset the ECU and went for a drive and WOW! What a change! Didn't realise how sluggish the engine was being before, must have been running pretty lean! Can't believe the 10 minute job could make such a difference.

I was hopeful that potentially it was a lean mixture noise emanating from the injectors, but it was not that, still there after the drive.

On the suggestion of a stethoscope I procured one off everyone's favourite auction site, and this helped me to realise the sound was in fact NOT coming from the top of the engine block - somewhat relieved, still confused.

Baffled, but sure it wasn't in the engine itself, I then thought I'd check the visible pipes AGAIN for any holes or splits, and I then realised that a pipe that was loose - that I assumed should have been loose - perhaps wasn't meant to be and seemed to have a tap connection that it was disconnected from...see below video!

https://www.youtube.com/watch?v=gzuvrNBTgYc

So good news is, found the source of the ticking. I am assuming that the pipe you can see in the video is meant to be connected to this tap, but I've not been able to confirm this? I have left it at this point.

I don't know enough about the engine to know exactly what this pipe is or what it's connecting to, or what to do about the noise if anything - can anyone enlighten me and advise if I need to have any further concerns as a consequence of this?

Thanks to you all once again!

[Carolyn]

AH - just pop the little hose back on.  Job's a good 'un!

It's part of a system to catch petrol vapour from the fuel tank breather. All about being kinder to the planet. (Which is a good thing and to be encouraged)

[ThisWill1992]

Great thank you - I did scout for some pictures of the engine bay online but the only ones I could clearly see the pipe, it was disconnected! Any reason for that at all?

I am assuming that the reason the noise rears it's head when warm is something to do with the fuel/air mix when the engine is up to temperature? It starts within moments of the idle revs dropping.

As I haven't been able to work it out - what is the pipe running to on the right side of the engine bay? No markings on it to suggest what is is.

Thanks!

[Carolyn]

Great thank you - I did scout for some pictures of the engine bay online but the only ones I could clearly see the pipe, it was disconnected! Any reason for that at all?

As I haven't been able to work it out - what is the pipe running to on the right side of the engine bay? No markings on it to suggest what is is.

Thanks!

It's a kind of holding tank for petrol vapour.  The vapour gets sucked back into the engine under certain conditions.  The little blue valve opens and shuts to allow this to happen.. It's often referred to as the 'charcoal cannister', which is a mis-noma.  American models do have charcoal cannisters, I believe, we just have a system that recycles vapour.

[ThisWill1992]

It's a kind of holding tank for petrol vapour.  The vapour gets sucked back into the engine under certain conditions.  The little blue valve opens and shuts to allow this to happen.. It's often referred to as the 'charcoal cannister', which is a mis-noma.  American models do have charcoal cannisters, I believe, we just have a system that recycles vapour.

Good to know, thanks! I guess I just wasn't recycling any vapours in that case! That may have been what was contributing to a slight smell after I'd been driving in that case.

You have all been very helpful, thank you for your help and support! An easy fix for an initially worrying problem 😁

[Ardent]

That's what we are here for.

Please don't disappear now issue identified. Join in.

Start an hello thread.

[ThisWill1992]

That's what we are here for.

Please don't disappear not issue identified. Join in.

Start an hello thread.

That is my plan!