Never assume anything when working with a TPI was a recent lesson.
I've really enjoyed the last two years of owning my first Corvette. I did the usual replacements like injectors, IAC, fuel pump, regulator and filter, temp sensors and a few relays. All good? Well mostly. After all that it was a great runner but there was a couple niggles left. One was that the throttle was sticky coming off idle and second the idle speed would at times be high at 900 or so. Usually the RPM's would eventually settle at 650-700 but after running at highway speed and then onto slow road speeds the idle would be slow to drop to 650. I chalked it up to a bogus IAC so I planned to order a premium replacement along with a throttle cable. Then I had some thinking time while taking a summer evening drive in my favorite car.
I knew a vacuum leak or another uncontrolled air would throw off an idle setting but I've been through the whole system and all was solid. Then for some reason I thought of the sticky throttle issue and why it only felt that way when the engine was running. Bingo! The throttle plates were corking shut. With no air getting by them the only other source was through the IAC passage. The puzzle was coming together. The IAC was trying to open so far to let enough air in for idle it was messing with the ECM. The bad assumption? That the base idle was correct. Wrong! I immediately drove home and got to work. The anti tamper cap on the throttle screw was gone so the clue was right there all the time. After a couple hours work and finishing at 1 in the morning I took her for a shake down roll. I didn't get home until 3. I felt so much better I was having fun expanding my carbon footprint. Remember, Base idle....base timing.....base everything before anything else.
Now I'm off for another drive....Not much more fun than a well running, well driving Vette.
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TVaitonis
Adams' Apple
