Engine valve noise

My Tacoma has 239,000 on it. Its a 2007, has a 2.7 (4cyl) engine. When you lug the engine, after it's warmed up, (mostly between 35-50mph), prior to it downshifting, has a lot of preignition/detonation valve noise. I've had the engine analyzed, and there is no check engine light. I am wondering if it the timing chain might be getting worn, or the tensioner is not working properly, which might be causing timing advance or retard issues during acceleration. Any thoughts? The analyzer gave a clean read out, and that everything was within parameters.

 

What grade of fuel are you using? You may want to try a higher octane, especially at your high mileage.

 

What is "preignition/detonation valve noise"?

 

Good question. OP pick one... Those are three different things.

1.) Pre-ignition = The premature combustion of the fuel–air mixture in an internal combustion engine before the spark plug ignites.

2.) Detonation = Occurs when combustion of the air/fuel mixture in the cylinder does not start off correctly in response to ignition by the spark plug, but one or more pockets of air/fuel mixture explode outside the envelope

3. Valve Noise = Noise made by the valve train when running either normal or excessive.

From your description you are getting a spark knock or detonation caused by lugging the engine. It would probably help if you used a higher octane fuel. Also try not to lug down the engine when driving.

 

Have you ever had your valves adjusted? I'm pretty sure they are a shim in bucket style so you would remember paying for it. That being said, valves usually get tight, not loose, but it might be worth while to pull your valve cover and check your valve clearance.

 

There is no shim -in-bucket for the 4.0 liter engine. You replace the entire bucket if adjustment is needed. I posted the PDF for 4.0 liter valve adjustment in another thread a few days ago.

 

Same concept. The method to adjust them is the same.

 

Not quite. For a shim-in-bucket setup, the cams remain in the engine. For the 4.0 liter 6 cyl engine, the cams are removed to get the buckets out.

 

But the OP says he has a 2.7 not 4.0.

 

Yes, but its the same principal. You measure the bucket instead of the shim, but its the same idea.

And the 2.7L is a shim in bucket.

 

That would be correct for the Older 2.7 and 2.4 engines ( 2RZ and 3RZ ). For the modern 2.7 liter engine 2005 and up 2.7 2TR-FE uses hydraulic adjusters and has no shims or buckets .



Below is the 2.7 Liter 2TR-FE setup:

 

Thanks for the clarification on the newer 2.7 - yes - my 2004 2.4L 1st Gen used shims.

 

In answer to "don't lug the engine" and get higher octane fuel, the vehicle calls for normal 87 octane. Lugging the engine is not intentional, it's just when you're in 4th gear and slowly accelerating prior to downshift. That being the case, you should still not have valve noise. What it looks like now is that the timing chain is stretched/worn, tensioner is all the way pushed out; there is slack in the chain. That being the case, it would seem that timing advance or spark advance through acceleration is a problem.

 

Oh, and higher octane fuel didn't help. Tried it. See previous post. Looks like the timing chain is stretched/worn.

 

Well with 239K Miles it may be stretched a little. Get a new timing chain installed...

 

Yep, getting it done here in a week or so. I will update this post after complete. Thanks Jimmy

 

4 tanks with

$25 bg44k BG 44K fuel system cleaner power enhancer 11oz.

bg44k or techron ...back to back...should clean it up some

of all the snake oils out there, either of these two actually do make differences