1. Check the NGK spark plugs you got to make sure they are the correct ones for the application. If you got the standard (non-platinum) plugs, they should be BKR5ES11 or BK…R5EYA11 ..
2. Double check to make sure the plugs are gapped at .042 ". If you got the correct plugs, they are normally pre-gapped at .044". It's pretty close to the actual recommendation of .042", but just to be sure I'd take them out to check, because if they are set at .044" rather than .042", the gap would be a bit too wide and could be a possible cause of stalling..
3. Make sure the plugs are all seated correctly, to the proper torque..
4. Make sure the spark plug wires are good and all firmly connected to the plugs and distributor cap. Be sure that no wires are accidentally "crossed"..
5. Make sure no vacuum hoses accidentally came loose while you were doing the spark plug change job..
6. Are the distributor cap and rotor brand new? For the optimum tune-up, it's recommended that those (and the ignition wires) be replaced along with the spark plugs. (MORE)