Engine knock at start, continues for 15 sec then nothing

Just like the title says, I went to start my truck to leave school and it had a medium loud knocking sound for 15 seconds, then it stopped. It wasn't at all like the truck had time to warm up, it only continued for about 15 sec. The strangest thing was right before it stopped knocking there was a rattling sound like something re-aligned and then it was gone.

Do you guys have any ideas?

Ill check the belts and pulleys when I get home, but didn't really sound like that. I'm hoping this is a distinct problem that someone can recognize.

 

does the engine run rough, like the timing is off and then straightens out to a super smooth idle?

 

not at all actually. it started fine and just did this briefly. I know what some valves can sound like when they are dry and cold right in the morning and it wasn't that. Really strange.

 

What year and what engine?

 

Toyotas, run great... Sound like shit

 

Pretty typical Tacoma knock it sounds like.
Did it sound vaguely "dieselish", but much quieter?

 

You'll get cold engine piston slap on occasion,,especially pronounced when running cheap grade gas.

 

How long has this been going on? When was last oil change? Was the correct oil filter used?

I always say if you ask for help, provide us with detailed information. Year, model, engine, transmission, etc. Hard to offer help with only 10% of the information. But I would look at the oil change situation. If it is not the correct oil filter, then that can cause oil drain-back and knocking noises.

 

was it just once? or does it do it every time? sounds like the head was dry, but it shouldnt take 15 seconds to get oil pumped up there, maybe it just felt like 15 seconds because the sound was so horrible?

 

Thanks for the input guys. Sorry I need to put more info in my sig, but it is a 99 standard cab 2.7l. 123,500 miles on the truck.

It's actually funny you mentioned cheap gas because this is the first time I just filled up with Arco gas since I've owned the vehicle... Coincidence?

As for the sound, it definetely sounded like piston slap, it was that awful deep sound that we all know...

As for the oil filter, I do all my own changes and I recently went with a wix filter for the first time about 600 miles ago. The guys at the auto part store said they had a wix rep come in and compare the insides of it to a k&n and the are almost identical...

And to answer your question about the frequency of this, it just happened once, and I would say it lasted a solid 10-15 seconds. Long enough for me to open my door an listen for a couple seconds...

Good info guys! But I hope it isn't the filter thing, there was definetely no problem installing the filter and it was about the same size as the one I pulled off.

 

Mod--- reply #7 is right I have the same problem in cold weather 20 degrees to -20 degrees I get valve tapping it quiets down after the engine warms up. I have less or no noise with 93% octane.

 

Cold temps (dense air),,and cheap fast burning gas,,maybe with some moisture in it pops in the cylinder pretty hard,,more of a bang then a ping. Higher Oct with the slower burn rate usually will not do that super fast burn,,like cheap gas. Cheap gas,,can break piston skirts due to this high mileage cold ambient temps slap.

Lets hope you didn't hear chunks of skirt aluminum passing thru the gullet of your motor. Because it can kinda sound like chunks in a blender,,then sound gone with no visible side effects.

When my motor piston slaps,,it's not due to cheap gas. It's because I didn't let it warm a few minutes. If I happen to jump out on the road,and I get that slap,,I IMMEDIATELY back out of the throttle. A couple miles of easy throttle management so things can warm,,then all is well.

Don't take it as the fix for your problem ELTacoma, keep a wary ear out. If it does it again,,be afraid then. I might contemplate pulling a valve cover,,just for a look see.

 

Good info man, sounds like some wise words. The weather isn't very cold here, maybe some 30 degree mornings, that's about it. It's really interesting that the gas can cause these side effects. Ill play around with a higher octane.

What would the pulling the valve cover tell me about this? I've been itching to pull the cover on this truck since I bought it to check the valve clearances. I know these 2.7s will burn valves if not checked, especially after the 150k range.

Where in Washington ya from? I lived up there for a while and would love to move back sometime.

 

Timing chain tensioner, I Believe is oil pressure operated that could be your culprit

 

Well, pulling the cover will give you peace of mind more than anything. A easy access to a big mechanical part of the motor to look for anything afoul. Like I posted, I would contemplate opening it up just to make sure everything is as it should be. Not a have-to-do thing.

Never heard the burning of the valves after 150K part. Never had mine checked with 203K on it now. It will sing right up to yellow/redline without missing a beat if I feel like it, runs good, plugs look good, compression is right up there front to back.

I'm about 35 miles north of Portland, Or. A little town called Castle Rock next to I-5.

 

This part could cause a loud knocking sound? I believe the oil pressure is ok.

crazy the truck hasn't made the sound since

Yeah I think theres kind of a myth about not having to check valves on these things. Some will stay in spec for 200k and some will be out at 100k, each engine is different.

I lived up in Blaine for a while and lynnwood, but only driven through castle rock

 

Good one Pakrat.

The rattling and then resetting could have been cause by your tensioner loose on the chain, not holding proper tension. Then the oil pressure came up and reset the tensioner on the chain,,because it is oil pressure dependent to push out against the chain and take away slack.

The loud knocking sound you heard could have been the timing chain slapping the inside of the motor when there was no tension on it.

And that could have very well been the problem. Hard to say if that caused it or why it did. The real only way to check it is to pull the front of the motor apart where the timing chain rides and see if there were any witness marks left from the chain slapping the block and alum case covers. I would venture a unsure guess as to the possibly of chain guide breakage which would be gobbled up thru gearing, chain links, and such. Hence the valve cover pull idea to look for marks or broken trash. Some serious dissassembly that would require some cash and time to put it back together right (gaskets, ect). The obvious is lack of oil but I don't think that's the case.

Run it,,see if it does it again any time soon. Use good judgement. When you make it to your next oil change, bandsaw the oil filter apart and pull the pleats flat to look for metals if your still curious.

Now,,just to scare the shit out of you and on the slightly morbid side,,because I have been watching waay to may zombie shows. Had a alley Feline crawl up into the Accy belting of a older car I had, because the engine was warm and it was cold outside. The poor thing didn't have a chance at startup. Sounded like a immediately seized motor on startup, then no sound but the rumble of the motor. Didn't check it because it was over in a hundreth+ of a second. Headed home. Headlights started dimming. It had swung about and knocked the Alt wires off. I mention this because it is similar in a way of what you heard,,not with the drama involved. I was in college at the time and had no money. I asked around about the cat and no one in that area was missing one.

Castle Rock was on a Japanese hit list if they ever had the rice balls to overfly bomb us. For what reason, I have no idea. Just a lumber town. Everyone whips by here, and that's fine by us.

 

I vote against the chain tensioner pesonally. Yes, the tensioner IS hydraulically operated by oil pressure, but it also has a heavy spring, and a anti-jump ratcheting mechanism specifically to prevent low oil pressure from letting the chain develop slack with the engine off, or low oil pressure.