Last night, I replaced the plugs on the Grand Marquis. With 80000 miles now it seemed time. It had been misfiring on cylinder 5 (front passenger side on a Ford), so I replaced that coil. As it turns out the gap on that plug had eroded to over 70 thousandths (should be 54), which was probably the source of the misfire – not the coil. But since I had the coil, it went on too. I cleaned the MAF as well. The responsiveness, smoothness of idle, and fuel economy have all noticeably improved. I’m gonna have to put the G-Tech meter in the car and see if there’s a quantitative improvement in performance as well.
It’ll be good to have a baseline against which I can compare the post-exhaust performance, too. I expect a minor but measurable increase from the upcoming 3″ single exhaust update. I ordered a handful of 3″ mandrel bends this evening (from Columbia River Mandrel Bending – great prices, great service), a stainless 2×2.25″ to 3″ merge collector, and a 3″ polished stainless tip (Magnaflow – from Summit). It should be here in time for the weekend. I’m excited. :)
BTW, the stock exhaust is 2.25″ from the manifolds through the cats and into the resonator, then it necks down to two inch after the resonators, finally coming together to a single 2 inch pipe – which is even less than 2″ in the compression bends. I’m sure a single 2.5 or even 2.25 would be adequate, but the cross-sectional area of two 2.25 inch pipes is about that of a 3.4 ich pipe, so I figured 3 would be better. Nevermind that I couldn’t find any smaller tips that I like, and I think it looks silly to have a small pipe feed into a larger tip. So, 3 inch pipe to a 3 inch tip it is. :)
