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Hi, have you checked your thermostat, does it have one on.
In order for it to enter into closed loop the engine coolant Must be at normal operating temperature let me know if this solves your problem.
The requirement to go into closed loop are
Some GM car will slip back into open loop at idle and that is completely normal. If you can raise the RPM to over 1200 and get closed loop, you are OK.
The zero reading for idle air control counts is abnormal, and should be investigated. This indicates that the computer has driven the IAC completely closed in an attempt to bring the idle speed down to it's target range.
This usually indicates an air leak somewhere, as you seem to have suspected when you were searching for intake manifold leaks. You may want to check also for air leaks at the throttle body, brake booster, EGR valve, and anywhere that a vacuum hose runs to. Try pinching any vacuum hoses off as close to the engine as possible, while watching the scanner for an increase in IAC counts or a change in idle speed. Often you can locate small air leaks by spraying a light mist of 2+2 gum cutter or other fuel system cleaner spray at possible points of leakage, such as the intake and throttle body.
Remove the IAC valve from the throttle body and check for carbon deposits holding teh pintle from closing completely. If this happens (it is common) the IAC will never close completely, and the IAC counts on the scanner will read at or close to zero because the ECM is trying to colse the stuck valve. The pintle and seat can be cleaned with the same spray colvent you use to leak check, and a toothbrush if required.
I hope this is helpful; if so, clicking my accept button would be most appreciated... thanks!
The customer has stated the the engine idles properly and has no idle problems whatsoever. This would not be the case with 0 counts on the IAC. I suggest that the data may be indicating the throttle percentage trather than the IAC counts. All the previous talk abvout vacuum leaks is useless if the car idles fine.
All this has nothing to do with the original question of "what is required for closed loop operation" which I correctly answered. I suggest you ignore all the vacuum leak talk by the other specialist. Please click on the accept button for MY answer which was the correct one.
That's another thing I meant to address. That is not normal operating temp. They use a 195 deg thermostat and that's pretty critical for maintaining closed loop. I once had a Chevy van than failed emission due to jumping in and out of closed loop and the problem turned out to be a brand new thermostat that just wasn't calibrated correctly. New thermostat, problem gone.
I'd start with that T-Stat. We already know that is a problem. Then see if the O/2 is a problem after that.