98 GTX LTD missing at around 5K rpms

[Grim]

I had a new issue come up today while on the river. While riding about 4K rpms all was good, then I went to 5K and above and it started missing, missing enough to cause slight power loss. Last time I was on the water I didn't have this issue. I did have a slight miss but it was barley noticeable and random. Now it is bad. The spark plugs are about 6 months old. I am going to remove them and check to see if they are fouled up. Last time I removed them they were wet with oil. Could this be the issue, if so what is the solution. As a side note. I am running a little premix in the gas plus the normal oil system. I did this because it hasn't been ran in 9 years. I originally started with 3 or 4 gallons premixed and last week I add about 5 gallons gas with no added oil to dilute it more. I am using ethanol free gas at 89 octane.

 

[etemplet]

Just replace the spark plugs and see what happens. Running extra oil definitely causes fouling and can diminish performance a tad. I know people that run both Premix and the Oil injection system. Peace of mind I guess. I'm not arguing. I like the higher octain fuel you're running.

 

[Grim]

Here is a pic of the spark plugs, definitely oily, how does color look to you guys?

 

[Jeff Berner]

I had a new issue come up today while on the river. While riding about 4K rpms all was good, then I went to 5K and above and it started missing, missing enough to cause slight power loss. Last time I was on the water I didn't have this issue. I did have a slight miss but it was barley noticeable and random. Now it is bad. The spark plugs are about 6 months old. I am going to remove them and check to see if they are fouled up. Last time I removed them they were wet with oil. Could this be the issue, if so what is the solution. As a side note. I am running a little premix in the gas plus the normal oil system. I did this because it hasn't been ran in 9 years. I originally started with 3 or 4 gallons premixed and last week I add about 5 gallons gas with no added oil to dilute it more. I am using ethanol free gas at 89 octane.

I had same issues and changed out plugs and gap at .035 my engine tag says.043 but will foul plugs on start up, ran great for a couple hours until new gremlins came out and quit charging