ok, when im cruisin on highway or around town, and i thro in Neutral,or idle to let the car warm up, i get this idle sweep, it goes from like 700 to 1200 RPM, i can see the sweep on my RPM, as well as my wideband AFR (lean to rich, the whole dam range), and vac gauge, it sweeps from -16in HG to like -21 or -22in hg, some times it happens all the way till i stop, some times only a few sweeps.. sometimes, not at all.. it dosnt matter if the engines warm or cold, its done it in both situations.

every thing is clean, IE, the engine is a fresh build with only a a few K on it (if that), I cleaned the TB, and the IAC...
CAS has NO burnt wires (no EGR), and i dont get a cel. I also hear a high pitiched tone coming from the engine bay, idk WTF it is? im 100% sure its coming from the ECU, and it does it randomly, sometimes during the idle flux, some times while the engines idling fine..

Ive swapped the following with my other venge, and it still runs fine:
Map
IAC
TPS
CAS
new Gasket for TB (incase it was leaking)
new PCV valve.

*Fuel pump is new (walbro 255, as well as the fuel filter)
injectors are clean, the car drives fine otherwise, just the dam idle while coasing or sitting..

also the map sensor has a missing link and FCD (its bypased until i get this issue resolved. so no boosting)

wtf could it be, and what is the high pitched tone, is that an indicator my ECU is crapping out? i dont know of ne sensor that if bad would make my car idle the way it does...

Check for leaks at the IM gasket and injectors. It may also be the upstream o2 sensor.

It is normal that some ECU's make a loud whining or whistling noise during the o2 sensor heater diagnostic.

hmm, the ill check th einjectors, but i know the IM is gtg, when i idle, and its idling normal, i dont see any vac loss, ist ~-18hg, but ill check for sure. ne thing else?


also, i dont think its the IM, i have my vac line running from there to my Aeromotive AFR, and i have a guage in the cabin, and during those sweeps, the FP dosnet change or bounce, one would think if the vac is changing at the IM, it would effect the FP too since its Vac dependant.
my Boost gauge, which i see bounce from -16 to -22inHG, is located on a seperate vac manifold, and it sees the flux..does that sound reasonable?

so, i was lookin in the engine bay, and found that my front O2 sensor was loose! it was rattling around and (when cool) i could hand tighten , loosen it. now since ive tighted it, the problem isnt as persisant or as big, but i havent driven it that much yet, so u think this could have caused the prob? should i reset my ECU and let it re-learn now that the 02 sensor isnt intermittant>?

How the hell could that have possibly happened? Well, you found it. Resetting the ECU (and subsequent cruising) would be the quickest way of getting things in order, if the loose oxygen sensor was the only issue.