2003 Corvette 5.7L 350HP spark knock (detonation)

[Jerome P.]

Under a hard pull in first and second gear the engine develops spark knock. I have been told this is common with the 5.7L-350HP engine.


Is this correct? If so, what can be done to correct it?


Other then this problem the car runs great. I have routinely changed the plugs every 15K miles. The car has 35K miles on the clock. I always purchase name brand gas, but in AZ the highest unleaded octane gas available is 91. Are there an additives available that are recommended?

[Richard M.]

Re: 2003 Corvette 5.7L 350HP spark knock (detonation)

Consider a bottle of GM Fuel System treatment PLUS, P/N# 88861011 (in Canada, #88861012), at oil change time which will remove intake system and injector deposits. GM does not recommend any other fuel system cleaner.
Also GM had a TSB on 2001 and 2002's concerning replacement of the rear Knock sensor located under the intake manifold, but check to see if you have any
trouble codes first, you can go to Autozone and have it scaned for no charge.
You should not have to change plugs every 15,000 miles.

Best regards,
Richard

[Edward J.]

Re: 2003 Corvette 5.7L 350HP spark knock (detonation)

Jerome spark knock at high RPMS or under accel is a rare problem, I generally see spark knock problems at lower RPMS or when climbing a hill. Just for your info the original AC Delco spark plugs are good for 100k which sounds like a lot of miles but they will go there and farther. GM's T.E.C. will help if there is a carbon problem or a lean fuel injector but you may not see results for a few tank fulls of fuel. and if you have some time to take a trip to run it hard alittle bit to help with clearing out the carbon.

The LS motors are one of GMs best running and fuel sipper V8's made and have few problems but make sure that there isn't something else the matter. commons issues are broken valve springs and roller rockers that have come apart and lost there rollers. these problems do have noises when runing at idle. and a broken spring is something you surely don't want to let go.

[Tom H.]

Re: 2003 Corvette 5.7L 350HP spark knock (detonation)

Do a google search on LS1 piston slap. I've heard lots of that in these cars, but cannot recall hearing spark knock. I have driven hundreds of C5's, not just a few !

[Edward J.]

Re: 2003 Corvette 5.7L 350HP spark knock (detonation)

Do a google search on LS1 piston slap. I've heard lots of that in these cars, but cannot recall hearing spark knock. I have driven hundreds of C5's, not just a few !

Tom, the piston noise is more of a cold start issue and really will not have any outcome ,The car can live for its entire life that way. It is one of the more common issues.

[Tom H.]

Re: 2003 Corvette 5.7L 350HP spark knock (detonation)

Tom, the piston noise is more of a cold start issue and really will not have any outcome ,The car can live for its entire life that way. It is one of the more common issues.

Yep. Very familiar with the issue. Was just making sure that's what the OP wasn't hearing.

[Clem Z.]

Re: 2003 Corvette 5.7L 350HP spark knock (detonation)

make sure they did install the correct spark plugs as this could be a problem if the wrong plugs heat range were installed. also make sure you do not have a exhaust leak from the air pump.