I am running a 2.3L stroker with all the boltons including a FP Red. My car was running great except for a very rough idle, even after a tune. I just changed to a 1 step colder racing NGK sparkplugs and the motor is now much more smoother. Could it be the sparkplugs??? The original ones had only 17k miles on them. Also, the new NGKs are about a quarter on an inch longer than factory ones, is this ok?
Thanks

 

What are the numbers of the plugs you started with and the colder ones you switched to?

 

it could be the gaps on the plugs causing the difference. what were the old ones and what are the new ones?

 

Another thing that could help your idle, unless you already have it, would be a good coil on plug pack. The new plugs with the higher discharge spark current should help you out, they did great for me. The plug gap could have effected the rough idle, how did the plugs look when you pulled them? A lot of soot on the end?

 

Sounds like your old plugs were a little fouled out. I change mine with every oil change or two. IMO, they're pretty cheap and almost always make a slight difference.

 

As Turbodoug suggests at 17K miles, your original plugs were probably fouled. This could be related to the type of driving that you do. If you do a lot of stop and go, city driving with a lot of time spent idling the motor in traffic, then your plugs will tend to foul out sooner than if you do relatively, high speed, highway driving. Also, your particular engine build may factor into the equation, as a more radical camshaft grind may not idle as well as the stock cams or the milder grinds. So, this could also tend to loadup the plugs, especially given excessive engine idling periods.

In general, a colder plug will tend to foul easier than a hotter heat range plug given the same driving conditions. I don't do much stop and go driving but I change my plugs every 2,500 miles(4,000 Kms.), or every other oil change, as Turbodoug mentioned.

 

agreed check spoolinup.com in the reviews his coilpack is way more reasonably priced and works awesome ask TTP