even the 99c plug gapper works fine if you get them all even and are carefull. Most plugs will fire within a fairly large range of stock, but it is more an issue if they aren't consistently gapped, esp. on a wastespark system.
But I disagree that it is plug gap.
If he was having a misfire due to plugs then his AF gauge would spike Rich,not lean as there would be unburnt fuel in the exhaust from that event.
Instead he is experiencing a lean misfire from it going lean, and the subsequent surge. This has to be outside the ignition system.
Possible causes are:
- dip in the MAF voltage showing less air coming in and therefore fuel is reduced even though there is no real change in airflow; could be a faulty MAF (I had one do this to me
)
- same thing as above, pcm sees less air than is really present but instead it is introduced by a momentary vacuum leak. Such leaks can be caused by a cracked hose/line/gasket that vibration or temp changes could open up temporarily and allow unmetered air to enter.
- faulty O2 sensor showing a sudden rich condition that the pcm corrects by leaning out fuel
- intermittent connection on a single fuel injector/plug/wire
The next step in this thing is to compare the upstream O2 sensors from both banks while cruising and see if the lean indication is present on both or just on one bank. This could narrow that particular problem down greatly and get you on track to finding the original problem.
