I have a 98 Grand Prix GTP with a service engine light that every 3-4 days comes on after clearing it. I have replace the spark plugs, ignition wire and the 1-4 coil. The car runs great, I do not feel any misfire and no drivability issues. So what is next?

Art

Swap injectors.

When was the last time intake manifold gaskets were done?

Check your coolant level too. A coolant leak in the intake gasket can cause misfires.

Thanks. But I don't feel any misfire. There is no rough idle or drivability.

Art

When engine light comes on, scan for codes. What is the problem code number?

The code is p0301. I have replace the spark plugs, ignition wire and the 1-4 coil. The car runs great, I do not feel any misfire and no drivability issues. After clearing the code and the light, 3-4 days later it is right back on with the p0301 code

Art

May be worthwhile to do a compression test on cyl 1.

But the PCM is seeing the misfire, thus the P0301, You've already swapped wire, coil and plug around, now, just like everyone else will suggest for the diag process, swap injectors around and see if the code stays, or moves to the cylinder you swapped with.

OK, so I should switch the #1 injector with #3 or #5 and see what happens. Correct?

Art

Definitely swap injectors and see if the code follows the same cylinder #1. Have you checked if the (ICM) ignition control module is getting voltage to all coils. Another scenario I have seen is the crankshaft position sensor (CPS) acting up and not sending a signal to the ICM to spark a coil

I've also seen ICM'* go batshit wonky after they get hot. But, that usually affects a whole coil which causes 2 codes. But don't rule that out either.