Buick high idle

[Dehaka]

03 ccentury drives great no codes. Idles high in park. Not as high in Drive or Reverse. Idles at 1475 in Park no AC little lower with AC on. Replaced lower and upper intakes + gaskets, mass air flow sensor, temperature sensor, thermostat, dash instrument cluster, head gasket, radiator, water pump, starter, idle air control valve, oil and filter, tranny flush and filter, power steering fluid, coolant, throttle position sensor, cleaned throttle body, ran smoke test and found no leaks all done by licensed shop.
Mechanic reflashed computer and it worked fine for a while then battery died and problem reappeared. Taking back to shop on Monday.
Any ideas for a permanent solution that wont poop out everytime i swap batteries?

Thanks for all replies.

 

[Lubener]

You have a vacuum leak as indicated with the MAP information which is raising your engine speed. I would recheck with an actual gauge teed off the intake manifold.

Also, if your engine was warmed up, I would check why the ECT is only showing 171 degrees. Either your thermostat is bad or the ECT is sending the incorrect data.

 

[Soft Cars]

Throttle Position Sensor. They can cause a high idle if they're not clocked correctly during installation. A common mistake is to turn them in the wrong direction to line up with the bolt holes. If you turn them in such a way that you're coaxing the throttle plate open, then there's your high idle. The correct way is to turn them in the direction of closing the throttle as you're lining up the bolt holes.

 

[Trav]

Any CEL or codes?

 

[Dehaka]

Any CEL or codes?

No codes of any sort.

 

[Trav]

Fuel trims?

 

[mk378]

If it's not drive by wire, check for throttle cable sticking or adjusted too tight, or anything that could be holding the throttle plate open like Soft Cars said.

The bottom line here is that no engine can run fast without extra air, so find out how it is getting in.