When I start it in the morning it knocks or after it has been setting all day at work. It is really noticeable when I take off and get on the gas. It only does it for a few minutes them stops and doesn't do it until it sets for awhile.

Oh, it's a 2001 Tacoma with the 2.7L. The only mod I have done is a K-N filter and Amsoil synthetic and that was last year. I changed the oil and filter a month ago.

Any ideas? I will be taking it to Toyota tomorrow.

 

So its a tick, or a defined knock at start-up?

I am trying to figure out if this would be valvetrain related vs. block related (rods, pistons, etc)

 

It is a defined knock.

 

Sorry for the hijack, I'll get this out of the way fast-
96- love the look of your black steel rims, probably because its loolking alot like my rig (same color, and I've got Tech1 rockcrawlers.

Okay, back to your normally scheduled thread...

Possibly just a bad tank of gas? Have you added some dry gas or fuel injector cleaner to see if that helps?

Sounds like you're running a little lean until the engine warms up.

 

Excessive piston slap maybe.

 

Why would this happen?

It doesn't sound like the ping you get from bad gas. I filled it up the other day while this problem started at the end of the last tank. I always use 76's 89 octane.

 

Thanks! You and Brian and some others were my inspiration. I just love the look!

 

I think it is piston slap. my 2.7L did it, and from what I've read, MANY 2.7's do it. I think that the consensus is that it is OK, it is just an annoying tapping during first start up when the engine is completely cool. Nothing bad is happening. Here's an article that describes it. I posted on this board about it back when it first started happening to me.

http://www.canadiandriver.com/articles/jk/020320.htm

a quote from the article. "In the past, the sound of piston slap meant trouble. Worn cylinders, damaged piston skirts, or cracked pistons were common causes, and all meant expensive repairs. Now things have changed.

Engine designs have changed to make them more compact, lighter, with less internal friction, and higher revving. To do all this, piston design had to change, and some of the major changes are shorter piston skirts and straight piston skirts. The short, straight skirts allow the piston to rock more in the cylinder, and we hear it as piston slap.

Closer manufacturing tolerances have helped reduce piston clearances and slap, but some engines need more piston clearance to allow for piston expansion. During the first few minutes of operation, the piston can expand several thousandths of an inch, yet clearances are typically in the one to two thousandths of an inch. Fortunately, the cylinder also expands, or we would find pistons seized.

On vehicles built in the last decade, piston slap that occurs for a few seconds on cold start is quite normal. My own vehicle, with only 30,000 km on it has piston slap for about 5 seconds when first started on a below freezing winter morning. Service information from General Motors states "A cold Piston knock which disappears in 1.5 minutes should be considered acceptable". From experience, I have found that piston slap that occurs only during cold starts and lasts only for a minute or less causes no problems. Just don't place a load on the engine until the pistons have expanded and the clearance has been reduced. "

 

I was thinking the same thing!

 

ewarnerusa,
Thanks for the info. Maybe I will dump the Amsoil and run the regular stuff and see how that does.

 

I think it will do nothing. I say keep the amsoil, and let the truck warm up for at least 10 seconds before driving. I used K&N, Amsoil, and stock filters in mine and I didn't notice any differences. I never tried any experiments, though. I don't think that piston knock is in any way related to air flow, maybe with octane. but the article sounds like it is just a matter of expanding metals as the engine warms. good luck. nice truck!

 

I think he meant the amsoil oil...

 

OH, I see now after rereading the first post. it seems like the amsoil oil would be great! I'd keep that, too.

96 -- those black rims look sweet. I want black rims on my green truck, too. someday....

 

Yep, my 2.7L 2001 does that as well. My 96 Tacoma with the 2.7L did it also with no other problems. Would seem to be the nature of the beast.

Let the truck warm up some before moving if this bothers you.

 

Ben, there's been some lively discussions of this phenomenon on the TTORA national board over the past year and everyone who has followed up, researched and seen this through has come to the same conclusion. It's "normal". One guy posted an official comment from Toyota, where they stated basically the same thing that has been said in this thread; if it only occurs during cold starts, it's just the parts coming into tolerance.

I am curious why you would want to dump the Amsoil. It seems to me that this is all the more reason to have a good, clingy, synthetic oil in place during cold starts.

 

Rob, I was reaching on that comment. I am not going to dump it for the reason you stated.

I have been searching every board and have come to the same conclusion, "it's normal" I still have the factory warranty so I am going to take it to Doxon anyways. I want to hear them say it. Plus if something should happen down the road they will have record of it.

 

My LS-1 had that nice little chitty chitty "bang-bang" on a cold start. (nerve racking even though they tell you its "normal") Check and make sure your running the correct weight oil. We put 10-30 in my dads z-71 and it called for 5-30. It knocked like a son of a gun on start up.

 

My '95 4R knocks around 3k on the tach...never hear it any other time though. Weird stuff.

Christian - Definately diggin the steelies man! I love mine!

Fink

 

My 2.7 does it too...just give it a chance to warm up.

In the summer, however, it never does it. Wait 'til the weather warms and keep an ear out.
(BTW, I am running Amsoil too, nothing but goodness from that stuff)

There is one other thing that makes a little noise on cold mornings...but I am trying to remember the name of it. "Resonator canister"...? I really don't remember. Anywho, I'll take a listen on the next run if it happens and give you my opinion.

Jim

 

Well, I am going to take it to Toyota and let them tell me what they think.

I have a 2003 Dodge with the Cummins turbo diesel (company truck) and when I start it in the morning it has serious piston slap.

I guess I will let it warm up or crank the stereo before I drive in the winter.

Thanks for all the $.02.