5.3 L engine noises

rocknrobby · December 28, 2005

I have a 2000 GMC 1500 series serria 4X4 with the 5.3 L V-8 engine. The truck currently has 102,000 miles. Last spring at around 97,000 miles, I did replace the spark plugs, fuel filter, and PVC valve.

For the last couple of months, the truck has really been spark knocking with very little acceleration.

Now that it is cold, I live in Michigan and it is in the low teens lately, when I first start the truck up and take off, there is a very loud kocking sound that is even noticed by the little woman. After the engine warms up, this extremely loud start up knock goes away but then the typical spark knocking begins.

Is the start up knock that goes away a bad bearing? Are these (2) problems related to each other? Is there a fix for these problems?

Any help would be appreciated.

Thanks.

GM-Tech · December 29, 2005

There's a known issue with cold piston slap, but I would think you should have been experiencing that long before now. It typically starts around 15,000 miles or so. It's not harmful, but an annoyance.

Without hearing what you have, I couldn't say what it is. As for the spark knock, that'd require a bit of diagnosis too. Knock sensors on those have been somewhat of an issue, especially if you wash the engine. I wonder if the spark knock could have anything to do with a change in formulation of the fuel in your area for winter.

rocknrobby · December 31, 2005

There's a known issue with cold piston slap, but I would think you should have been experiencing that long before now. It typically starts around 15,000 miles or so. It's not harmful, but an annoyance.

Without hearing what you have, I couldn't say what it is. As for the spark knock, that'd require a bit of diagnosis too. Knock sensors on those have been somewhat of an issue, especially if you wash the engine. I wonder if the spark knock could have anything to do with a change in formulation of the fuel in your area for winter.

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