Mystery Ping pre-Detonation Sound on Acceleration
 

Ok, I've been searching threads here for days and looking at similar issues people have had. I've tried basically everything I can think of and all the suggestions in similar threads. So far I'm still at a loss as to what's causing this issue and how to fix it.

I have a 1989 4WD 22RE Pickup. I've been replacing parts and fixing things as I find they are ready, the truck has 286k miles.
Recently I replaced the timing chain with LCE's dual row conversion kit, metal guides etc.
After I did the timing job I took it out for a spin, everything seemed great (at least much better than before on this old truck).
But then I started to notice THE SOUND...

THE SOUND is definitely some sort of ping, pre-detonation or something of the sort.
It happens under the following conditions:
About 10-15 seconds after the engine first starts and warms up...
Only on Acceleration or Gass Peddle Release De-Accel.
Most noticeable past 2.2k RPM.
When Downshifting down a hill and slightly tapping the gas peddle (its Loud), you don't here it until you tap the gas.
I can accelerate and hold certain RPMs and it's hard to hear, but comes back as soon as I let off slightly or accelerate more.

In pursuit of finding a cure I have:
replaced a bad TPS with a new one, which helped a little
cleaned my Mass Airflow Meter (one spec was testing out of range, after cleaning was back to spec)
Filled up with Premium Gas
Adjusted timing (with jumper) 5, 8, and others
Double checked distributor gear was set on the right tooth.
A while ago replaced the Oxygen Sensor (ebay sent me one labeled MR2 - Land Cruiser but the electrical connector was the same so I'm assuming it's the correct one)
Listened to Injectors with stethoscope, they all sound about the same, like the're working.
Added almost all new vacuum lines (I think the one going to the charcoal canister is still original and there are two going to something just above the cold start injector timing switch which are also old)
New Plug Wires
Done my best to test EGR system (without real vacuum gauge) but seems to be good.
Also I just tested my coil, primary coil resistance is 0.9-1ohm (spec 0.5 -0.7 I think?) Do you think this could be the culprit?
Also I've pulled the EFI Relay a couple times to clear codes, and it seems like this gets rid of the problem at first, at least until the engine warms up, but after reaching past 2k rpm it's back.
One suggestion I haven't tried but will soon, is to plug the air injection tube, in case the fuel injectors are not atomizing all the way and some liquid gas is detonating after the cylinder when oxygen is reintroduced.

I will upload some sound files for reference here:

I would appreciate your thoughts.

Most of the way thru the description I was thinking that's rod knock and not predetonation.

The audio is clearly to me an air leak type vibration and not a gnome under the hood with a hammer. I expect you'll find an issue with the pair/as/EGR related plumbing either the hoses, vsv's or vacuum modulators.

Thanks
 

That is certainly mechanical.

Sounds like a mystery! First thoughts are rod knock or valvetrain noise? I have this theory about the 22-RE valvetrain. (And I don't mean talking nicely to it so it won't tick)
I think the adjusters on each rocker wear from "flat" to somethin sloped over time: the wear pattern makes it so that when you adjust the valves over the life of the engine you reach a point where the wear mark looks like a small "slide" aka mountain or driveway.

At certain RPMs the tapping sound we hear (at times, not the normal tolerance clicking) is the valve kicking the rocker arm, we, off it's rocker! Here I mean it moves it (compressing the spring) away from it's intended location for a very short duration. Could this be happening?

I listened again. The sound is of a constant frequency? It does not move with the RPM, right? If yes, you can rule out my "theory" above and start looking for what the other dude said: loose screw somewhere. Heat shield could very well be.

Hmm
 

Well I'm going to run down to Autozone and rent a vacuum pump/guage later today so I can sus out the rest of my vacuum system, EGR, VSV's etc.
I will check the heat shielding but to be honest when your're right there with the hood open it does not sound like a flat piece of metal on the exterior of the engine.
As for the frequency of sound, it does match the rpm speed.
I will take another sound clip from infront of the engine instead of the cab, it's quite loud when the hood is open.

I've adjusted my valves a number of times fairly recently in the hopes that it would help, but I don't think it's the same sound at all as regular valve ticking. This is much worse.
But I was wondering about something similar with the rocker arm and springs before. I don't know if that's possible or not.
What makes me think it's something else is that I've been able to start the truck and rev it for a short time with no unusual sound for a short period of time (before it heats up or before oil pressurized?) This is what I what I'll try to get a clip of.
It's strange that it seems to have something to do with the ECU in that i've noticed some initial difference after resetting the EFI Relay. However this could be pointing again towards vacuum leaks messing with injection timing, no?

Man my age is getting to me, my hearing is flakey!
:nopity:

Today it sounds like a gnome with a hammer.

Are you due for an oil change soonish, maybe even if you aren't, drop the pan and check those rod bearings. Does its ever make this noise free reving in the drive way while parked?

Anyways what I came in to say was there is a logic chart in the FSM for the air valve. You would be able to correlate the sound with any of these change points if it's that system.

Another source of odd acoustics is running a non OEM air filter.

...
If it was the valve train contacting the cover it would do the tap constantly and get louder and faster with the RPM.

...
Regarding tappet wear and slipping the rocker over off the valve. It would take a broken spring. The wear is linear left to right in the rotation axis.

Thanks for the feedback!
 

Thanks for all your thoughts. Today I got a vacuum gauge and went through my vacuum lines more thoroughly. I pulled off my EGR and shot some carb cleaner in while moving the valve. There was definitely some carbon build up in the tube but it seemed ok, better after some cleaning but I don't think it was stuck open or shut. The funny thing was after I put it back together and went for a drive. I had started the truck and idling sounded fine, rev'd it up a few times and it sounded good! I was nearly sure I had solved it cause the noise was gone.... until I started up a hill outside of town, then it came back. I drove up the hill a little and then in neutral the engine died. Started back up, let it idle and it died again. I had to give it gas to keep it running until I got home. I thought maybe I missed a vacuum hose or something, but they were all plugged in. Back at home I decided to test all the VSV's. After they all seemed to function fine, I started the truck and it idled fine without a problem. This type of subtle inconsistency is strange to me. Gnomes are starting to seem more plausible at this point...

I will look into the sound chart. I have a Hanes and a Chilton. Your saying it's somewhere in one of those?

I did do the timing chain myself. I was actually fairly convinced that I might have done something wrong and the timing chain was loose, like maybe the tensioner failed or a guide came completely loose. The old plastic guides were pulverized so I dropped the oil pan and cleaned it good. But after talking with a tech at LCE Engineering who thought that the tensioner failing was fairly unlikely, I began exploring other options. I'm not ruling it out, but since it's a bigger job than other potentials I decided to evaluate other options first. I have yet to pop the valve cover again and see if I can see some slack in the chain.
As for the valve cover, I did tighten it a little more this time than I have previously (I used to just go by the visible squish of the rubber under the nuts) but this last time I decided to go by a torq spec from the book. I kept tightening it, past what seemed necessary even though I had not yet reached the specified torq in the book. I will try loosening, but my thought was similar that If the valve cover was interfering I would hear the sound all the time and not just under certain circumstances like I do.
And yes it does make the sound in all gears.

Here's a sound clip from under the hood. This is after checking and cleaning the EGR etc. Notice how the first couple revs sound ok (considering it's fairly worn out as is, valves are loud etc.), but then the sound just pops up after a little bit like the Gnome had to finish his sandwich before pulling out his hammer.
I hear it first at about 9 seconds into this recording.

I know that sooner or later I just got to rebuild this thing. But non the less, I would love to be able to figure this out.

I think this guy is living under your hood:

https://cimg3.ibsrv.net/gimg/www.yot...9a1e7d653e.jpg


In all seriousness:

I am no noise expert, but that sound really sounds like a mechanical sound from inside the engine.

My ears say that sounds like a valve train noise, but my limited experience with these types of noises means I am not that sure.

Even though I agree that a valve cover that is too tight should cause a noise all the time, that is where I would check first.

You could take the valve cover off and see if you see any marks on the underside of the valve cover where the rocker arm made contact.

The valve cover nuts do not get tightened down much at all. The factory specification is only 52 inch-pounds which is about 4.3 foot-Pounds.

Unless you have an accurate inch-pound torque wrench, I think just tightening the nuts until you see the "squish" of the rubber grommets is a good indicator of how tight the nuts should be.

Other than that, nothing comes to mind that sounds like your noise and would happen under the circumstances you are hearing it.

Thanks for playing Stump the Chumps! :D

https://cimg3.ibsrv.net/gimg/www.yot...5c3c0aec6b.jpg


:safari:

Could be the the chain tensioner? It is very possible op torqued it doen way to much, hindering it's operation.