engine knocking while accelerating

flavaflave2 · January 11, 2016

Truck has 200,000 miles fresh old and filters. Need to replace fuel filter, plugs and wires. Feels sluggish like not much power. When I drive you can hear a knock and it's constant and steady only when in drive or reverse. Never happens on park or neutral. Previous owner said a valve is knocking but I'd like to get some more opinions on this. Need this truck to last awhile really hope it's not a valve. The exhaust is weird it only has 1 cat pipes connect to one muffler. Please reply if you have any information and I will do my best to go into more detail

Formulabruce · January 11, 2016

Problem is the wrist pins, ( Piston slap) a defect due to short, light piston weight and non correct pin placement and silicon coatings. GM wrote extended warranties on this so they didnt have to rebuild engines. It not usually an issue that causes anymore than noise. Sluggish could be the cat. A compression check could tell more. If you take the plugs out, I would put some COPPER never seize on the threads and re gap before install.

The noise under load is more typical of piston slap. Exhaust sounds correct to me

flavaflave2 · January 11, 2016

Problem is the wrist pins, ( Piston slap) a defect due to short, light piston weight and non correct pin placement and silicon coatings. GM wrote extended warranties on this so they didnt have to rebuild engines. It not usually an issue that causes anymore than noise. Sluggish could be the cat. A compression check could tell more. If you take the plugs out, I would put some COPPER never seize on the threads and re gap before install.

The noise under load is more typical of piston slap. Exhaust sounds correct to me

wouldnt the piston slap occur all the time? (in park or neutral)

flavaflave2 · January 11, 2016

Truck has 200,000 miles fresh old and filters. Need to replace fuel filter, plugs and wires. Feels sluggish like not much power. When I drive you can hear a knock and it's constant and steady only when in drive or reverse. Never happens on park or neutral. Previous owner said a valve is knocking but I'd like to get some more opinions on this. Need this truck to last awhile really hope it's not a valve. The exhaust is weird it only has 1 cat pipes connect to one muffler. Please reply if you have any information and I will do my best to go into more detail

There is also possibility that my piston rings are shot it loses oil somewhere and sometimes blows blue smoke on startup

Formulabruce · January 11, 2016

The noise occurs only under a load, which makes it a piston, wrist pin, Ring issue. A morning at 10 degrees will have it doing all the time till warm up. Motor needs a rebuild, but its worth it if the body is good

flavaflave2 · January 11, 2016

Problem is the wrist pins, ( Piston slap) a defect due to short, light piston weight and non correct pin placement and silicon coatings. GM wrote extended warranties on this so they didnt have to rebuild engines. It not usually an issue that causes anymore than noise. Sluggish could be the cat. A compression check could tell more. If you take the plugs out, I would put some COPPER never seize on the threads and re gap before install.

The noise under load is more typical of piston slap. Exhaust sounds correct to me

There is also possibility that my piston rings are shot it loses oil somewhere and sometimes blows blue smoke on startup

00Silverado4x4 · January 11, 2016

Is it possibly spark knock. That would be an indication that you may have carbon build up in the engine or you also could be getting bad gas (low octane).

flavaflave2 · January 12, 2016

Is it possibly spark knock. That would be an indication that you may have carbon build up in the engine or you also could be getting bad gas (low octane).

no the noise occurs every time I start up and go to drive the more I put my foot on the gas the quicker and more tappier it sounds. I don't know how to diagnose that

flavaflave2 · January 12, 2016

Is it possibly spark knock. That would be an indication that you may have carbon build up in the engine or you also could be getting bad gas (low octane).

if it were spark knock wouldn't it do it in park or neutral as well? I can rev it as much as I want in park or n but it doesn't make the noise till I'm in gear

00Silverado4x4 · January 15, 2016

Not necessarily, spark knock typically presents itself when the engine is under load, as in driving. My truck does it as well. I've used the fuel treatments and have greatly reduced the spark knock. My only other options now are either an engine flush or starting tearing the engine down and manually removing the carbon build up that I know I have.

Formulabruce · January 16, 2016

1. LS engines do not build up much carbon, unless the rings are gone and its a oil deposit. Tghese are fuel injected and fuel is well separated at injection, and timing and temp are controlled for proper burn.

2. Older LS engines are Not made for the week E85, and will drink a lot more fuel to do same work.

3. More work, = more heat from using E85.. any octane boost will improve things

flavaflave2 · January 18, 2016

1. LS engines do not build up much carbon, unless the rings are gone and its a oil deposit. Tghese are fuel injected and fuel is well separated at injection, and timing and temp are controlled for proper burn.

2. Older LS engines are Not made for the week E85, and will drink a lot more fuel to do same work.

3. More work, = more heat from using E85.. any octane boost will improve things

so you think using an octane booster will make the noise go away?