neocon

my car is getting detonation when i start it up. it only happens like 1 out of 3 times i start it but i was wondering what is causing this and how can i fix it. i have a 01 Gt with a vortech s/c and dyno tune. thanks

97targa

Sounds like your tune. The timing is prob retarded a little too much for cold starts! The timing curve changes once it warms up, which is probably when it was tuned.

Dan04COBRA

Are you sure its detonation and not piston slap?

neocon

wut is piston slap and what does it sound like

Dan04COBRA

Piston slap will sometimes be a consistant sound and othertimes be more irratic like detonation. The fact that it's not happening with every start, wouldmake me think it's not your tune really.

It has no 'thud' to it, it's a fuller sounding 'tick' almost.

Maybe you can pick up a couple gallons of 100+ and mix it in & see if it helps with the sound. If it doesn't, I'd really look at it like piston slap.

neocon

is piston slap gonna damage my engine or no?

Dan04COBRA

That is debatable.

Many people with 99-04 Mustangs or 4.6's have piston slap, majority never have an engine failure or premature wear. Some have failures.

My 02 GT was a victim of piston slap. Once it started I got about 10k miles out of her before Ford replaced the shortblock.

97targa

My 2000 Silverado with the 4.8L has Piston Slap. Sounds just like lifters! It's one of those common GM ****ty annoying problems! If I give it gas for a lil bit and get some oil pumpin the sound goes away! "They" (GM)say the pistons expand when they heat up, thus the sound dissapates...My truck sounds just like marbles being shook up in a coffe can for 2 or 3 seconds NO LIE. Then it dwindles down but stays there all the time. It did it since the day I bought it with 46kmi on it. Now it has 69kmi.

lizzyfan

Yea, GM are notorious for piston slap. I actually have it on my Ranger with 243000k (yea you read it right) with no, knock on wood, problemo's
Annoying sound for the most part. I'd have to hear a clip of it!