Knocking Sound
Thread Starter
Cruising
Joined: Jun 2010
Posts: 12
Likes: 0
Knocking Sound
OK I have a 1986 Corvette completely stock with 28,000 miles on it. The problem I'm having is a knocking noise coming from the engine. When the engine is in park and I rev the engine it sounds great no problems at all no matter how high I rev it. But when I put it in drive and give it some gas it starts to make a metallic rattling noise especially around 2800 rpm. I also noticed that when the engine is cold it doesn't make the sound. But when its warmed up it will start acting up. The hotter it is outside the more it will rattle or knock. I have changed the plugs and fuel filter recently but it did not help. oil pressure is good and not receiving any codes. Any ideas from anybody. Thanks.
Burning Brakes
Joined: Mar 2008
Posts: 881
Likes: 24
From: Coquitlam BC
There's a good chance that it's your cats and that the honeycomb inside is loose and rattling around inside. Mine did the exact same thing as what you're describing and it really sounded as though it was coming from the engine when it wasn't. Mine also didn't do it until it warmed up, and the hotter the engine got the worse it was. Check your cats.
Thread Starter
Cruising
Joined: Jun 2010
Posts: 12
Likes: 0
Yes I have put premium gas in it which made no difference and as far as the cats go I put in a new front y pipe with pre cats eliminated. Also pulled the old cat off and put in new high flow cat. So i don't think its the cat or fuel grade issue.
