: LT1 Spark Knock

03-11-07, 07:55 PM
When starting my 96 FWB after it has warmed up, I hear a knock noise when it starts up. Someone told me it was spark knock or something. What causes it and how do I fix it? Thanks!!

03-12-07, 01:09 PM
To verify if it is spark knoock you would have to either take it to a mechanic who has engine diagnosis systems (computer) or get yourself a cable and software and hook up your own computer to see what the BLMs and spark knock counts are reading. Typically spark knock will occur when the ignition system has a problem or even if the fuel system (i.e., pump) is not providing fuel properly. I suppose knock sensors could be going bad, but typically those are good for a long time and hold up well.

Do you get the knock only when the car is warm (or hot)??
If knocking only when cold I would guess exhaust manifolds have a leak, which is common.
But if you get a knock when warm then that is a little odd. Scanning the car realtime would be the next best move to se what is going on in there...

03-12-07, 06:28 PM
Thanks. I guess i will get it on a machine this week. It only does it when the engine is warm. I think it might be something in the ignition because i get some rough idle at stop lights every now and then. Is it normal for the furel pumps on these cars to be a little noisy. It sounds a little whiny when i stand at the back of the car?

03-14-07, 01:03 PM
If the pump is louder than usual then it could have a restriction in it or just be failing...

But a new "non-GM" pump I installed once was noisy from day one. It was just built that way.