Why does my chevy 2.9 liter 4 cyl. truck knock when i start it?

Asked by Jun 13, 2013 at 09:57 AM about the 2007 Chevrolet Colorado LS Extended Cab 4WD

Question type: Maintenance & Repair

When my truck is cold and i start it i hear a engine knock. Knocks for a couple seconds then goes away?

6 Answers

435

This is because it takes a few seconds for cold oil to get all the way from your oil pan, in the bottom of your engine to the very top of the cylinder head to the rocker arms. Try changing your oil and using marvel mystery oil with a good synthetic oil like penzoil ultra. I had the same problem in a few of my vehicles and that did the trick. Marvel mystery oil has been around for a long time, and honestly there is no other product that actually works. knock off brands dont work. only marvel.

Best Answer
435

i forgot to say, the oil takes a while to get to the rockers because of deposits left in your engine by old oil and the wear of your engine, over its entire life.

Well, that's true skinnyginnie but it's a 2007, shouldn't have sludge unless it's been neglected about oil changes.

435

six years is plenty of time to accumulate deposits, neglected oil changes or not. especially with regular, non synthetic, low detergent oil.

1 out of 1 people think this is helpful.

Thanks!!! We will try changing oil and using that marvel mystery oil!!

435

When you do change the oil and use marvel, give it about a week of driving before the knock will go away. Its like soaking really dirty dishes in soapy water. the soap needs time to dissolve the dirt.

1 out of 1 people think this is helpful.

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