Tapping Noise On Acceleration

[QUIKAG]

I posted a thread a while back (I can't find it) where I mentioned a slight rattling noise, but it's more a tapping noise under more than light throttle at lower rpm. I was told it might be the heat shield on the exhaust manifold on the passenger side. I was also told, it might be the radiator tank rattling around.

 

I fixed both of those potential issues by taking a screwdriver and pulling the heat shield away from the passenger side exhaust manifold. It did seem pretty close in a few places. I also wedged some duct tape between the radiator tank and the fender and another side. It's snug now. The tank did rattle a little bit when I shook it, so I was hopeful.

 

Unfortunately, both of those attempted fixes didn't work. It's a pretty light tapping noise under moderate throttle at 2,000-2,500rpm or so. It doesn't seem like valvetrain as the motor runs great otherwise. Could it possibly be the VVT????

 

Any help would be appreciated. Otherwise, the truck has been great, but this tapping noise is a bit of a distraction from otherwise good engine sounds.

[jro909]

i have the problem too...on my 5.3 it reminds me of the chatter 6.0s make under load...

[Stevens03]

You sure its not spark knock? What grade fuel are you using. You could need to run 91 octane or better.

[SCHSIERRA]

I have the same noise, and I run 93, always have. I sounds like it's coming from the left side of the engine compartment. It doesn't sound consistent with the engine RPMs so I don't think it's lifters. I also don't think it's injector noise because the more gas I give it the louder it gets but it doesnt change how many ticks it does. Also, I think it only does it while in gear.

 

I drive a 2008 GMC Sierra 1500 W/T 4.8 LY2 with 13,600 miles. Has done it since I can remember.

 

My 4.8 doesn't have Variable Valve Timing or Active Fuel Managment so I don't think either are related.

Edited February 20, 2010 by SCHSIERRA

[QUIKAG]

I run 93 octane, primarily Chevron exclusively, so it's not knock. It's at low rpm under load, but not WOT. Maybe anything between 30-50% of throttle between 2,000 and 2,500-2,800rpm or so. Above that, either the sound goes away or the engine noise drowns it out.

 

It's really not a metallic sound per se, it's more of a tapping noise maybe 2-3 times a second through the above rpm and throttle parameters.

 

It's quite odd and I'd like to get a diagnosis because it makes the engine sound a little lame and one of the main reasons I bought this truck is for that sweet 6.2L motor.

[SCHSIERRA]

I can't duplicate the sound while in Neutral, Park, or Drive with my foot on the brake. It's only while driving, although speed doesn't seem to affect it. I think it has a popping, ringing, and tapping sound mixed in one. I think it sounds exhaust related. The ringing noise I can duplicate in neutral going down the road, but once I take the load off the engine, the popping and tapping go away.

 

As you said, QUCKAG, it doesn't sound metallic.

Edited February 20, 2010 by SCHSIERRA

[QUIKAG]

It's good to know quite a few people have a similar issue, but it's a bit concerning no one has a fix?

[Darthmalo]

It's good to know quite a few people have a similar issue, but it's a bit concerning no one has a fix?

 

 

I think I have this noise. But is only at lower speed. When I accelerate it goes away. I have the 4.8 engine.

[98 Z71 SLT]

I posted a thread a while back (I can't find it) where I mentioned a slight rattling noise, but it's more a tapping noise under more than light throttle at lower rpm. I was told it might be the heat shield on the exhaust manifold on the passenger side. I was also told, it might be the radiator tank rattling around.

 

I fixed both of those potential issues by taking a screwdriver and pulling the heat shield away from the passenger side exhaust manifold. It did seem pretty close in a few places. I also wedged some duct tape between the radiator tank and the fender and another side. It's snug now. The tank did rattle a little bit when I shook it, so I was hopeful.

 

Unfortunately, both of those attempted fixes didn't work. It's a pretty light tapping noise under moderate throttle at 2,000-2,500rpm or so. It doesn't seem like valvetrain as the motor runs great otherwise. Could it possibly be the VVT????

 

Any help would be appreciated. Otherwise, the truck has been great, but this tapping noise is a bit of a distraction from otherwise good engine sounds.

 

 

2 more things to check

 

see if your cylinder #7 exhaust bolt broke off. these exhaust manifold bolts are prone to shearing off. take a look at the driver side exhaust manifold-to-cyl head bolts, closest to the firewall

 

if that's ok, then you may have a leaking exhaust downpipe donut seal. we had a few in the shop awhile ago.

[pm26]

I run 93 octane, primarily Chevron exclusively, so it's not knock. It's at low rpm under load, but not WOT. Maybe anything between 30-50% of throttle between 2,000 and 2,500-2,800rpm or so. Above that, either the sound goes away or the engine noise drowns it out.

 

It's really not a metallic sound per se, it's more of a tapping noise maybe 2-3 times a second through the above rpm and throttle parameters.

 

It's quite odd and I'd like to get a diagnosis because it makes the engine sound a little lame and one of the main reasons I bought this truck is for that sweet 6.2L motor.

 

You may have a defective knock sensor. What it may be doing is advancing ignition timing too far and then pulling back when audible knock occurs. Honda Odyssey vans had this problem several years ago. I was reading a number of complaints where the engines would knock regardless of the fuel used. Just a thought.

 

With a good knock sensor, even if you ran regular 87 octane in your engine, there should be no knock as the knock sensor should cause the ignition timing to retard somewhat, thus eliminating the knock. You would experience just slightly lower performance, that's all.

 

I do not know what kind of noise you are experiencing. What I described above would be engine pinging.

 

As Stealth pointed out in the post above, it could be a leaky exhaust gasket. i had those on my Nissan pickup at about 90k miles (their 3.0 liter V6s were famous for that) and there was this rumbling noise on acceleration until the engine got hot, then the noise stopped, because the gaskets expanded and sealed better.

Edited March 28, 2010 by pm26

[03blackz71]

I had a rattle every so often on my truck also. I did the heat sheild and coolant tank but no help. Then I found a tsb about the battery cable being close to the oil dipstick and it would vibrate against each other. What I did is zip tie the cable to the dip stick holder and the vibration noise went away.

[Darthmalo]

I had a rattle every so often on my truck also. I did the heat sheild and coolant tank but no help. Then I found a tsb about the battery cable being close to the oil dipstick and it would vibrate against each other. What I did is zip tie the cable to the dip stick holder and the vibration noise went away.

 

Do you have the tsb number?

[03blackz71]

Sorry no I don't have a number of the tsb. I think they say to reroute the cable but I just ziptied them together and have had no more issues for over a year.

[z06killr]

Did you ever find out what was causing this?

 

No sounds at start up, idle, free rev, or throughout first gear 900-6000RPM that i can hear. If I do a manaul gear select and keep it in first and mash the gas/brake to load the engine/let the RPMS climb I dont hear anything.

 

I dont think its anything internal like a bearing, wrist pin, lifter, etc as it would scream out at me in 1st under load.

 

Here is a video of it. This is from a stop up to 4th at about 40. You can really hear it around the 49-55 second mark.

 

Could it be detonating/pre-ignition from bad knock sensors? I was going to burn up the rest of this 87 and run some 92 and see if it helped.

 

Transmission/converter?

 

 

[dbroman3]

I know this is a while ago but any update on a fix. The youtube vid from Z06killr is exactly what I have in an 2007 6.2 I purchased recently.

Edited July 8, 2014 by dbroman3