allright i know this isnt going to be very specific but i just got a 93 suburban 2500 with a 454 the engine is making a clankin noise when it is running... also very hard to start have to hold the gas pedal down to get it to fire up and when it is running it is dumping fuel into the tbi.. i was wondering whter you guys would hav and idea of where to start. also it doesnt wnat to move.. i was thinking maybe start by pulling the valve covers off to see if a rocker arm is broke or a pushrod.. let me know what you guys think any help is appreciated..was my brothers and then something happened while driving to caus this noise to happen and it overheated and melted some plug wires.. so put new wires and plug when my dad put them in he put 6 on and the noise wasnt there but then he put the other two in and the noise was very obvious i hope he didnt blow a hole ina piston...

 

I think you need to begin by checking for codes...then checking the compression

 

This kinda sounds like what happen to my wifes grand am it started clunking really loud and what not. It ended up being a valve spring broke and bent a rod. Like argon said check for compression.

 

id do a compression test immediately. i bought one and had a really hard time starting it. it clicked and knocked and eventually spewed oil everywhere turned out to be holes in the pistons.

 

I understand how springs and and rods get broken, but how do pistons get holes burned in them?

 

There are a couple ways. If the cylinder is running lean it can get hot enough to melt a hole. If you break a valve spring you can beat a hole when the piston contacts the hanging valve. Nitros can burna hole as well using the same principles as running lean.

 

I figured on the nitrous and spring thing. I never thought about the leaning out thing.

 

thats exactly wat happened tbi was goin out and ran it long