99 Lumina Injector or Coil?

Hello this is my first post.

I got a call from my friends' mother a while ago. She has a 99 Lumina with a 3.1 and 61,000 miles on it. A few days ago, all of a sudden it started to miss with the engine in drive and at idle. It runs smooth in park. She also noticed a slight drop in acceleration at times. At that same time the 'Engine" light came on and stayed on. The 'Service Engine Soon' light did not come on at all.

When this first happened I said she should remove the fuel filter and blow through it to see if it was plugged because of the mileage and a low fuel flow at the rail valve where i checked the pressure. I didn't have the special tool used to remove the filter and having lost my Snap-On MT2500 scanner to theft several years ago, I told her to go to a shop and have the filter replaced first because it was time and I didn't want the fuel pump to get damaged from restricted flow.

She replaced the fuel filter and sure enough it was plugged bad. The fuel pressure and flow are now fine. She also had them test it on their scanner. It showed zero missfires on the 2,3,5, and 6 cylinders, several hundred missfires on the number 1 cylinder, and many thousand missfires on the number 4 cylinder. The man pulled the number 4 plug and said the plug was firing and the compression was good. I'm not certain but I think the center coil fires the 1 and 4 cylinder.

Would I be right in assuming the center coil is the problem or could it be an injector? I felt the injector and it was ticking so it seems to be working without me knowing if its plugged. The oil didn't smell like gas.

Could the number 1 secondary post on the coil still fire alot better than the number 4 post on the coil? What's the best way to test the coil? Could it be a plug not working under load? The reason I'm thinking 'coil' is because it happened all of a sudden and the two cylinders in question go to the same coil.

I haven't worked on cars since I started locksmithing and the OBD2 system is Greek to me. Any help would be appreciated.

Ed.

It could be the ICM or the coil, I think Autozone will test them for you. Since 1 and 4 are the same coil, this does sound ignition-related, however you can check the injector resistance to see what condition they are in.

It could be the ICM or the coil, I think Autozone will test them for you. Since 1 and 4 are the same coil, this does sound ignition-related, however you can check the injector resistance to see what condition they are in.

The last DIS I worked on was an 88 3800. I remember there being one driver in the ICM for each coil and a common ground for all three. I was thinking if this was still the case on this car then the ICM would cause both cylinders to miss the same way because they fire 180 degrees apart so I never thought about the ICM being bad.

I guess my best bet would be to remove both and have them tested like you say.

Thanks
Ed

Well the electrical tested fine. After a good injector cleaning the problem was fixed.

I dont understand how injectors with 61,000 miles on them can plug up so badly even though the fuel filter was pluged but that is what happened. Rhe car always ran Exxon gas. I now know they dont make them like they used too.

I hope this helps others.
Ed.