I would definitely be leaning towards a mistimed engine. When something like that happens the engine will seem to run ok off idle but while idling the misfire will be more prevelant and noticeable.
#PIP3433D: SES Light and Sever Engine Misfire On Cylinder 1 And 4 or Cylinders 2 And 3 - keywords ICM ignition miss module no P0300 P0301 P0302 P0303 P0304 plug repeat replacement spark - (Jul 24, 2007)
This PI Supercedes To Remove 2007 Model Year. Please Discard PIP3433C
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Some customers may comment on a severe engine misfire and a SES Light. Upon inspection, DTCs P0300 - P0304 may be found due to misfires on cylinders 1 and 4 or cylinders 2 and 3.
If this concern is encountered, inspect circuits 406 (IC Control for 2/3 Coil) and 423 (IC Control for 1/4 Coil) for an intermittent short to ground or poor connection on either end. Depending on the model, these circuits may short on the AC lines near the AC compressor, on the transmission mount, or on the transmission lines where they enter the transmission. If there is no problem found with these circuits, inspect the ignition control module ground to ensure that it is clean and tight.
If there is no problem found after performing the suggestions above and the SI diagnostics lead to ignition module replacement, replace the ignition module as directed but also replace all of the spark plugs and clean the ignition module ground to possibly prevent future ignition module damage.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
#PI00434A: 2.2 L61 Engine Crank , No Start - kw break broken chain cylinder head knock lubrication no noise nostart nozzle oil timing - (Mar 22, 2004)
When servicing the vehicle with the VIN you entered, the following diagnosis might be helpful if the vehicle exhibits the described symptoms.
Engine will crank but not start, also makes noise while cranking. Condition may be caused by a broken timing chain.
A. A new S-Pin Chain p/n 24461834
B. A constant (no check valve) lubrication nozzle p/n 12577163
C. And drive parts.
Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance. This diagnostic approach was developed for the vehicle with the VIN you entered and should not be automatically be used for other vehicles with similar symptoms.
2002-2003 Chevrolet Cavalier) and (2002-2003 Pontiac Sunfire) and (2002-2003 Oldsmobile Alero) and (2002-2003 Pontiac Grand Am)