Originally Posted by Paul Workman
In my experience, I recall what a difference injectors (Accels) made, far as idle goes. At the same time my plugs were new and my coils were only a couple years old, as were the plug wires.
Back to the injectors: They were NOS at the time I bought the car, and only a couple years old. I didn't realize they were NOS at that time, and the tell-tale resistance readings didn't show up until the eve that Marc was about to dyno tune the thing.
Marc was adding fuel at WOT and the AF mix remained leaner than he wanted. He asked me about the injectors, and I told him they were only a couple years old. He told me they were stock (really news to me at the time!) and recommended 16 Accel replacements.
Once the new injectors were in place, the AF numbers responded immediately to fueling table change inputs, the car ended up with 432 RWHP (stock cams), and the idle was as smooth as a sewing machine (and remains so to this day, two years later!).
All that said, I stand by my position that my scanner was the best $$ I ever spent, far as sorting out over 41 different "goings on" in this, my second C4. And, most importantly, the O2 sensors (which I can tell ya from experience) can also roughen up the idle a little, and the scanner will put a finger on those rascals PDQ. (If you don't have a scanner, take it to AutoZone - or the like - and get a print-out of how everything is working. Being able to see what all is going on is soooooo much better than checking this and checking that, tho I too suspect that plugs, wires, or injectors to be the propblem)
One last thought tho... If you are running sans secondaries, at idle the primary injectors only are running, and the dwell time is "stock". Only after you go to above 1% throttle tip in does the secondary injectors come on, and the dwell time is adjusted to provide proper AFR for two injectors.
P.
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