When I turn my key to "on" my tach does a strange "bounce" about once every second, ticking up nearly to 300rpm. Bounce, bounce, bounce. This is not present in any way when the car is running, but 8 out of 10 times I get a bouncy tach at "on". Could be CPS? Been this way for months. No other indication that the CPS is fubar. No stalls, just low idle.
On a cold start the engine starts beautifully, roars to life smoothly, RPMs slowly even-out over the first 30 seconds around 1000, temps always reach 195F and fluctuate normally, no overheat EVER. Drives great. After about 5 mins running after cold start RPM moves from 1000 down to about 600, low but stable. But, at warm start the RPMs literally snap right to about 800 then level off back to 600 after about 5 seconds of chug, chug, chug. This "snap" is bugging me because its always followed by 5 seconds of "chugging". This is mild, but noticeable every warm start. She idles pretty low at about 600RPM, seems a bit low to me, and its not the smoothest idle. At this point LIM gasket should have been changed... fearing compression leak or misfire.
I know it has a small exhaust leak, needs the MAF cleaned too, and I owe it a lot of general maintenance I cant afford at the moment. Would absolutely love to rebuild the heads and install new LIM gasket and valve cover gaskets. No fluid leaks in cooling, oil, trans, or brake systems. Any idea what could cause such a mild, yet consistent 5-second chug on warm start, or why my idle is slow, or why my tach likes to hop? Thanks.