Gshock

My 94 4runner has 128,000 miles. The engine seemed good when I bought it, no knock and all the belts including the timing were changed at least 42k ago. However, I noticed a slight knock coming from the plenum area or the top block.It's noticeable around 1,500-2,000 and above that seems to go away and disappear. You have to strain to hear over the normal ticking of the lifters and loud injectors.

My oil was changed friday it seemed to go away for a bit and then comes back. I have to ' blip' the throttle to create that sound to notice.

I took it to the toyota dealership yesterday and the mechanic wrote this

" Customer states he is hearing a knock type noise at the top of the engine area at 1500-2000 rpm then goes away. Check and advise. Checked and heard normal valve ticking noise. No abnormal noise heard when checking".

However he did state the valve cover was leaking heavily. I checked my oil and and rechecked it and I had a hard time finding a reading.


If you watch the video and carefully listen, it makes a sound like someone running their fingers across a fan blade lightly...

heres the video below




[YOUTUBE]http://youtu.be/DfSYPkCnMic[/YOUTUBE]

it seems like I have a bad valve cover leak and possibly out of spec valve?

FML....

TylerH

I would have the valves adjusted before you make any major decisions.

Gshock

Yeah. I don't know how the mechanic could have stated it was ' fine'. It's intermittent so when you first start the vehicle when its running cold, its almost non existent. When I took that video it was warmed up for 5 mins for me to recreate the issue.

I have a warranty from the dealership I bought the truck from ( non toyota) so I decided to have everything checked out to use it as leverage,by having toyota inspect it.

I'm just not sure where to start leaking valve cover or adjusting valves. Might aswell do both....

I've owned the vehicle since this Christmas everything was fine till before the new year. I'm convinced I have a gremlin trying to destroy it...haha

abecedarian

if you're talking about the fluttering "budawhump" like noise after you let off the throttle, I'd say it's just resonance in the intake, particularly since it "appears" to be around the top end of the engine. If it's not much different whether cold or hot - 5 minutes running isn't enough to get all the engine parts like crank, rods, bearings, etc... warm enough to make a big difference - then you won't have much of an argument unless you invest some into figuring out where the noise is really coming from. And valves don't make a lower freq sound like what I think you're talking about and nothing up top will either.

One thing you may attempt is changing your oil but you didn't specify what weight oil you had put in so that could be a crap shoot. If you had 5w30 put in, which is typical, you may try going to a 10w40, 15w40 or even 20w50- you're in San Diego so a 10w or 15w oil could help and 20w is rated for use down to 0C/32F according to API specifications. If the noise goes away with thicker oil, you may have cause to believe there is something worn but has not yet become serious enough to be an issue overall. Rod bearings come to mind but they don't typically fail multiple cylinders at once so that sort of rules that out unless a previous owner didn't do oil changes regularly, if at all.

Another issue is you have a warranty, which means things will get fixed "IF" they fail during the warranty period. Unfortunately, "getting ready to fail" is not the same as "failed" so the dealer's under no obligation to troubleshoot or repair anything they feel hasn't failed. So what can I say? Drain some oil then drive it til it breaks then pour the old oil back in? That's not necessarily fair to them to treat them that way and who's to say that the engine won't last another 100,000 miles the way it is?

You can try using a different weight oil and see if the problem subsides. If it does, then maybe you can tell the dealer that and see what their response is... and likely it will be to advise you to keep using that weight oil since that shouldn't invalidate the warranty and will at least keep the engine running well longer than thinner oil would. Alternately, you could pull the oil pan and physically check bearings and such to determine if they are in tolerance, then present that to the dealer however I suggest using an ASE certified mechanic instead of doing it yourself for the sake of argument: you'll be out of pocket for that expense, by the way.

92dlxman

pair system? does it only do it when you let off the throttle?

93toyrunner2

Definitely the PAIR noise, which opens more when the engine is warm. Pull off your air hoses from the front drivers side of the intake plenum body to the air box on the side of the air filter box. You will hear the burping strange noise coming from the hoses at the same time you hear the noise near the top of the plenum.
Nothing to worry about.

abecedarian

5 minutes after a cold start- PAIR shouldn't operate. That let's air into the exhaust for the converter to work with but the converter isn't hot enough after 5 minutes to use it. on the other hand, that doesn't necessarily mean PAIR isn't being activated on a cold engine.

good catch!

but where is the PAIR valve and where does it connect to the intake on a 3VZ engine?

93toyrunner2

Gshock

It does it as i'm pulling on the throttle cable opening the intake up, or both. When I was driving around on New years, after an hour of driving or more I noticed it was progressively getting louder. It got loud enough to hear it easily from the inside the vehicle which I shut off out of concern. Then after hours of resting restarted it and the sound was gone and progressed again.


I wouldn't also be fixated on the 5 mins as I've mentioned. It becomes louder as it reaches normal operating temp.

From a cold start I can rev it and the sound is non existent. Around 10-15 mins is when its noticeable easily,

I will let the mechanic know about the intake pairing system, thats another possibility.

Thanks Guys

92dlxman

if the sound can be described as a gurgling noise, its the pair system. nothing to worry about unless it is acting when it shouldn't, which i would imagine make your o2 sensors send some wacky feedback to the ecu.

i have no idea of the exact functioning of the pair system so i cant tell you when it should/shouldn't be active

Gshock

Gurgling, or a go kart at the family fun center type noise. You can hear it in the video low frequency. Its hard to capture on a cell phone, but in person its noticeable.

So basically its some useless emissions bs that recycles exhaust gas like a EGR?

Or I guess it injects air into manifolds for a cleaner burn. But the downside to emissions crap is that makes everything malfunction, just like a leaking charcoal canister on a motorcycle.

When I had my Mitsubishi 3000GT VR4 turbo I just installed block on plates on the plenum, save me so many headaches....

opps sorry CA DMV!

Gshock

Ok guys, I took it to my uncles friend who is a mechanic. He looked confused when he heard the noise and claims its a piston pin thats loose or cam or valves.. But he didn't have time to open up the valve cover or look at the valves. He's just guessing..They'd actually told me the same thing which was they couldn't hear anything.. And intermittently goes away... I told him about the intake he just looked at me funny. HA! He doesn't seem to think that its possible for it to make a sound like that.

So when I left I opened the hood and notice a strange hissing from what looked like the PAIR valve(located near the firewall on the left side ), so how would I function test it? If the Pair is replaced anyone have an idea how much it would cost? I have another appointment with Toyota tomorrow to see what their master mechanic says.

But anyways I made another better sounding video.

[YOUTUBE]http://youtu.be/LdmhoDKFzi8[/YOUTUBE]

93toyrunner2

I can definitely hear the PAIR valve on the deceleration. Have you checked the PAIR valve hose that connects to the tubing at the bottom rear pass side of the upper plenum? See the picture in post #8 above.

Gshock

I tried checking with a flash light, nothing broken or leaking that I can see. Tomorrow ill look when there's more light, I could be checking in the wrong area. Who knows.

Gshock

Update!


I went to the Toyota mechanic and he came up and heard the noise this time. And claims'" it's a piston ring in the rear cylinder slapping". I mentioned the PAIR valve theory and he says " No, I've heard that sound before on similar trucks and 4 runners of the same year and it sounds differen't. This sounds like a internal engine sound"

But they quoted me at 4k to tear it apart and look at it haha! So far nobody has taken it apart to determine if its a simple fix like a out of spec valve.

I called the dealer to see what his response is. So far he hasn't called me back of course. What a Nighmare! Arghhhhhhhhh.

When I bought it I test drove it, started it up. No noise and after the test drive came back and opened everything up checked for leaks. It all seemed good. Pop'ed the hood and ran the engine hard that noise was never there. I engaged all the drivetrains including 4WD, Lo and HI etc. Everything was in good condition.


Man...... this sucks...

I got a ticking time bomb..

93toyrunner2

Well, you can keep driving it till it grenades, or you can run a compression test on it, and see what your results tell you. If you want to sell it, let us know. Someone here will jump on it for the right price.
By the way, did you ever check the oil level?

Gshock

I found a used engine for sale with a 90 day warranty for 1k... If all else fails I might go that route, Might even do a 3.4 swap.. When I had my 2001 Sport 3.4 was much more solid motor. My girlfriends mom had a 93 Toyota 4 runner and the headgasket blew+ other stuff and her car became a paperweight. Same thing happend to my friend who was in the Marines his wife had a toyota 4 runner too, head gasket blew.

Maybe other people dont have the same luck I did.. I wish it was a head gasket...

w1ndexxSR5

hey man i had a similar knocking and had no idea where it was coming from. Did you figure it out?

92dlxman

i did not notice it in the 1st video. not the pair valve in my opinion. that sounds bad. but dont lose hope. diagnostics through recorded media on crappy laptop speakers is not accurate. but to me it sounds internal, and you need to fork out some bucks and have it torn down, or do it yourself. its a good experience. just nuts and bolts man do not fear.

93toyrunner2

Have you ever been able to check your oil level since this first post where you could not get a reading? Just because you took it in for an oil change, doesn't mean that they put the correct amount of oil in the engine. You should see oil level within the spec markings on the dipstick with the engine turned off. If not add and recheck.