Ticking/Rattling sound at low RPM under acceleration

Just want to point out you said yourself sound went away with higher octane. Off track maybe not derailed.

 

Well I have the new plugs in, but I won't have a chance to put 85 octane back in and drive it until tomorrow. We'll see if the problem persists.

On a side note, the strangest thing happened when I was trying to do some compression testing. I was set up to measure with a harbor freight system, and was getting really low pressures. I chalked it up to cheap HF crap, and went and bought another from AutoZone. When I got back and setup with the new system, I found that my engine wouldn't turn over. The starter motor seemed to turn, but it wouldn't engage the flywheel. My battery was pretty old, so I went and got a new one, but still had the same problem. At this point I'm completely confused, so I decide to just put everything back together and see if that would help. And lo and behold, the engine starts right up after I put everything back. Obviously that was a huge relief - the last thing I want to do is troubleshoot a starter - but I have no idea why it worked when I put everything back. The only thing I disconnected besides miscellaneous engine bay stuff and my spark plugs was the efi fuse, that way my fuel pump wouldn't be running when I turned the engine over.

Edit: And it's worth noting that the engine turned over just fine when I was using the HF system, it was only when I came back frome the store after a ~20 minute delay that suddenly the engine wouldn't turn over anymore. It might also be worth noting that I didn't pull the fuse for my ignition system, but I did disconnect all 3 coils.

 

Does the sound go away with higher octane? Do you have a 5vzfe? If yes to both, it may be the Tacoma tick. I get a ticking sometimes with 87 octane. It goes away with higher octane. I haven’t noticed it too much lately at all, and before I usually noticed it in 4th gear around 3k rpm or so. I’d get that in the mountains more often for some reason.

When you compression test I believe you’re supposed to go for a drive and then do the test while the engine is still warm. The factory service manual specified how to do the drive and how soon to do the test.

Some maintenance I did that was probably overkill that you could consider:

Plugs, injectors, coils, wires, valve clearance (omg major pita, seriously), clean throttle body, clean IAC (careful on this one as you can make things worse, but it can be needed to fix a high idle), air intake filter, probably more I’m forgetting

 

Most of the time if your starter teeth or flywheel teeth break sounds are a god awful screech of from what I’ve seen anyway. How do you kno your starting is working but not spinning the flywheel? I’m assuming you have checked fuses? Also did you depress that gas pedal all the way while checking compression?

 

grease u joints or exhaust manifold, use 01-04 exhaust manifold, cast iron cracks

 

That’s not his video. I thought the same.

 

I started out with the engine warm, but being my first time doing a compression test, it took me a while to get everything ready to go. But I should definitely get a copy of the factory service manual. I disconnected my ignition coils just because it seemed like something I should do, only to find out later that if I hadn't I probably would've fried them; that was a close call I'd like not to repeat.

I guess I don't *know* that the starter was turning, but it sounded like a spinning motor. It definitely didn't sound like I broke any gear teeth. I didn't check any fuses, but like I said, when I put everything back together the truck started right up... which is the really confusing part to me. And yes, I depressed the gas pedal all the way.

 

So I was really low on fuel when I started all this, which turned out to be really convenient because when I filled up with 85 today I knew that I was running 85 and not some mixture of 85 and 91. I drove about 100 miles through the mountains, and I couldn't hear any ticking sound. I also noticed a very slight improvement in power. There is a hill that I usually cruz up in 4th gear at 50, and today I was able to cruz up it at 55. Maybe that's not significant enough to really draw any conclusions, but it seemed like an improvement to me. In any case, it would appear that this issue was rooted in the spark plugs (the only thing I replaced/serviced since last driving on 85). The plugs that I pulled out didn't look too bad - in my not expert opinion - but they came out a little easier than they should have, and the crush-style washers used to create the seal don't look very crushed to me. So either it was a bad spark, or the spark plugs weren't making a good seal and were leaking air. Kind of a boring ending to this problem, but I'm just happy it was an easy fix. I still want to do some compression testing, but I'll have to try again another day.

And just a shoutout to vern650, your comment convinced me to try replacing my spark plugs before trying anything else, so thanks for that!

 

Hopefully the success continues. I was surprised when it helped on mine as well.