"Rick Cantellya" wrote in message
news:EdKBc.155973$Ly.76035@attbi_s01
I have a '98 Pontiac Grand Prix (better known as our Grand Pile). The
last few days it has been hard to start and runs rough when it does.
At some point, it smoothes out and runs fine. I've scanned it and
received the following codes:

P0403 - Multiple Random Cylinder Misfires
P0303 - Misfires on Cylinder 3

Any clues as to the most common cause of these errors? Faulty
injector or coil pack? If so, any clues as to how to zero in on the
problem?

The basics are compression, fuel and ignition. Check the plugs, wires, and
cylinder compression. Compression testers are reasonably inexpensive, as are
new plugs and wires. You probably have a distributorless ignition, but there
would then be 3 independent spark coils with driver circutiry for each. Any
of the above could be failing. Low compression usually comes from bad
valves.