97' Park Ave missing under load
 

I have a 97 Park Ave with about 210K miles, It has been running well up until now. Recently while going up an incline (slight load) and in O/D the engine will develop a misfire. This problem occurred a few years back and I had a check engine light came on, after checking the code I found one of the coil packs had failed. I replaced all (3) of them and it had been running well up until now. The problem seems to be the same but I am not getting any check engine lights. I replaced the coil packs with the Dorman Coils. I am wondering if they are the problem. Plugs seem fine, I am using Iridium (NGK) plugs with about 44k miles on them. Plug wires were changed at the same time as the plugs. Any help or further troubleshooting I could do would be greatly appreciated.
Thanks in advance, Steve

Hi Steve,
What you might consider,
Have your vehicle checked for any pending codes. Post them here.
It does sound like another coil may be breaking down under load.
If you get a P0300 , that usually includes all cyls, where as if you get a P030X that should at least let you know which cyl is having a problem. Once you know that you can switch the coils and see if the code switches cyls. If it does , that is the questionable coil.
If it doesn't change ,go after the plug or wire for that cyl.

Hanky,
Thanks for the quick reply. I have checked for codes and didn't find any (so far). I will check it again this week when time permits. I am begining to suspect the coil packs. I can check the resistance on them and see if I get one that is suspect. The symptoms that it is showing were the same as the last time when it failed, but last time it set a code and told me which pack it was. This time not so lucky. Wonder if anyone has used the Dorman brand of coil packs, I have used some of their replacement parts in the past and have had some issues with them. I will keep you posted on my findings.
Thanks again,
Steve

For what it is worth,
Not all aftermarket parts are problematic, but some can be..
When possible , which isn't always so, we try to stick with OEM parts. Avoids a lot of extra work.

Finally got some time to work on the Park Ave again and think I have solved the missing issue. I decided if I am going to pull the plugs and check them out I might as well change them. I removed the #6 cylinder plug and found it to be finger tight, the plug itself didn't look too bad but had some soot buildup around the threads. I can only assume that it was loosing its ground once it heated up and led to the misfire. I installed some NGK platinum plugs and took it for a test ride and tried to get it to miss while under a load, so far so good. I will be interested to see how it impacts my MPG. My mileage seems to have dropped during this issue. Hope this helps someone who may experience a similiar problem. When all else fails go back to the basics.

Park ave plugs
 

Thought I would add some pics of the plugs for reference

https://cimg6.ibsrv.net/gimg/www.bui...fbcdbd0331.jpg

Fuel injected vehicles don't require premium fuel unless specified by the manufacturer.
Every so often , a tank full of premium will help clean out accumulated carbon in the cyls and on the injectors.