Engine ticking, strange symptoms

[Jonny]

Can anyone explain what might be going on here on my 5 speed manual previa?...

My engine was making a ticking sound related to rpm, just like I would expect from a loose valve on one cylinder. I did valve clearances and all valves were mid range to too tight. None at all loose. After adjustment they are all at a mid-ish value... .007-.008 intake and .011-.012 exhaust. The ticking is still there, unchanged.

However I pay more attention to it now and it goes away totally when I take my foot completely off the accelerator so that the car is decelerating in gear. If I then depress the clutch so that the engine drops down to idle speed it comes right back and it is there under all other conditions as far as I can tell. I'm assuming that the injectors are closed in the foot-off-the-gas decelerating condition when the noise is not there. If so, is it related to the cylinders actually burning mixture? Why? Or is it something else entirely?
jw

[Jonny]

Can the injectors themselves get noisy? The ticking is definitely happening at exactly engine rpm. At idle I can count the ticks.

[timsrv]

Injectors can be noisy, but typically not loud enough to hear them inside the van with the engine access closed. There are many other things that can develop clicking/ticking, but without hearing 1st hand, it's hard to get a gut feeling. When I'm troubleshooting noises, there are several ways to get to the bottom of things, but the process of elimination is one of the better tools at your disposal. To determine if it's an injector, disconnect one then start the engine & listen. The engine will run a bit rough, but it will run on 3 cylinders. Do this with each injector and compare. If you determine that one particular injector being disconnected decreases the noise, then hook it back up and pull the spark plug wire for that cylinder and try it again. If the noise goes away or changes the same as it did for the injector, then it's likely a noise associated with combustion (not the injector). Noises that go away when combustion isn't present are usually associated with exhaust. Rod knocks can also go away, but those usually aren't described as "ticking" sounds.........more like "hammering" or "banging".

I've also seen engine accessories make noises, but considering the distance the accessories are from the engine, checking for this might not be productive. Still, since sounds can carry, it might not be a bad idea to consider this. When checking for engine noises, I remove the accessory belts and start the engine. running it for a minute without belts won't hurt anything & can help you rule things out. I've been certain before that a noise I was chasing wasn't coming from the accessories, but did this test anyway only to find it WAS. I've heard alternators make knocking and ticking sounds that I was sure were internal engine noises, so it's worth a shot. Sometimes noises like this can emanate from the transmission and/or bell housing area, so that too might be worth investigating.

If you don't have special tools for chasing noises, it might be worth renting one. They make stethoscope type devices for pinpointing noise locations. I've had varied success with these. If it's an injector, you can put the probe right on each injector and compare. Another tool that's helpful is an amplified electronic headset with a directional microphone. I have a set called "Engine Ears" and it's helped me locate these type noises before (particularly helpful finding exhaust & intake leaks).

The above are the methods I usually use and out of these I'm almost always successful using one or another. Good luck & please let us know what you find. Tim

[Jonny]

I'm pretty sure now that my post is the result of the collision of shim adjustment noob and efi noob (my only other four wheeled vehicle ever, my trusty old Toyota truck of 30 years, is screw and locknut and carburetor).
My paranoia about leaving the valves unchecked for so long and my unfamiliarity with fuel injectors left me worrying that what seems now to be normal fuel injector operation was something more sinister.
Disconnecting the fuel injectors one at a time seemed to lessen the ticking slightly regardless of which one I disconnected, and since the ticking seems to be consistent with fuel flow I suspect I'm simply hearing cumulative injector noise.
Tim, thank you for all the great information you (and many others) provide and for your dedication to establishing a resource for us all. This site and its enthusiastic and knowledgable members has renewed my pride in my Previa. My truck of 400k miles is so easy to work on while the Previa is rather less so and I had come to view it as something of a quaint old albatross. Now I plan to fix it up good and take the tross to 400k too, flying high wherever it goes.
jw

[pdgizwiz]

I've had a similar sound in my '94. I only hear it at idle, but it bugs me because the engine is freshly rebuilt.
Just the other day I pulled the injectors out and replace the rubber bits that they're mounted in. I'd have done this before but I didn't have the parts on hand. The picture below shows these bits from another engine that I disassembled earlier. The two o-rings in the middle seal the fuel cavity in the rail to the injector, but the outer (identical) ones are described as "INSULATOR, INJECTOR". You can see the broken one at the bottom. In my "clicking" engine all of the insulators at the lower position have disintegrated into crumbs. For some reason this one seems to go before the others.
I hope to get it reassembled tonight and see if the clicking noise has disappeared. I'll report here either way.
3500

[pdgizwiz]

Sure enough - swapping all those rubber bits exorcised my noise! My theory is that the lower bit isolates the body of the injector from the fuel rail, and without it the action of the injector causes it to make contact with the fuel rail and make a noise.
Oddly, the O-rings that seal the fuel are still supple and rubbery, while the two identical "insulators" are either hard and brittle or obliterated. Different kind of rubber, it would seem.
Your results may vary of course. I hope your noise is as easy to fix as mine was.

[timsrv]

Thanks PD! That's good to know. I knew they were called insulators, but never would have thought they were there to insulate noise. I'll keep that little tidbit in mind next time I'm looking for ticking noises. Tim