my 2001 gt needed new spark plugs, and a new iac vavle. was careful putting new plugs in. {**** poor design} making sure nothing dropped down in cylinders, but when i started her up, there is a loud banging coming from engine. thought plugs might be to long, pulled same size, longer threads tho, does any one have any ideas what the hell happened?

 

did you properly torque the plugs? it could carbon knock from a piece of carbon falling off one of the valves due to the new plugs firing better. Could have also blown a plug out of the head from not having them torqued right.

 

I have never found any thing "**** poor" related to changing the plugs on our cars; in fact it is considerably more convenient than most other V8's I have owned.

That aside, and as Teej said, did you properly torque the plugs?

 

Changing plugs on these cars are very simple and are easy to get to. Sounds like you're doing it wrong.

 

I'm with TJ - Did a plug blow out of the head?

 

I would recommend putting the old ones back in, just to see if the new ones are a problem.

 

Almost sound to me the way you discribe it.
Like a piston is hitting spark plug..That wouldnt be to good.

Id recheck those plugs out for any signs of piston hitting them.

BTW.. these plugs are real easy to do, try doing plugs on a 93 LT1 Corvette.
now thats not fun, in the books its a 4 hour job and some serious arm scarring

Just my 2

 

one of the easist spark plug change cars there are...minus the whole shooting plugs outta the head prob

 

Is it a banging or like an old steam steam engine sound? I agree either a plug blew out or is getting hit.

And yeah %100 agree on LT1 plugs.

 

04-06 5.4 3V plug change is even more fun.