Take aprox. 60 to 80 second warm up to stablize idle (Manually hold RPM at 1,500)
Replace coolant temp. sensor 0 280 13 0026 and gasket
Replaced fuel pump check valve
Replace in tank filter
Replaced main fuel pump filter
Fuel pressure regulator replaced
Fuel pressure aprox 62 PSIG
When A/C switch is Engaged problem is more pronounced - again stablizes after 60 to 80 seconds.
Run and Idles normal (875 RPM) when "warmed" up.

Idle control maintains Idle after first warm up

Try cleaning the MAS wire and the grounds on the inside front fenders. Have you checked for and intake manifold gasket leaks?

The Intake manfold gasket was changed with the Temperature Sensor, and the ground were also checked at the intake manfold, both frenders and Control unit - used Deox IT D100L -25L (www.caig.com) treatment still have the same problem. I believe your are correct this is an open circuit problem when the the engine is cold.

This is a steady state probem as opposed to an intermittent problem - thanks for the input.

Take aprox. 60 to 80 second warm up to stablize idle (Manually hold RPM at 1,500)
Replace coolant temp. sensor 0 280 13 0026 and gasket (this is a 2 blade type blue in color) is the the correct sensor? (should it be white - as this was the orginal color removed)
Replaced fuel pump check valve
Replace in tank filter
Replaced main fuel pump filter
Fuel pressure regulator replaced
Fuel pressure aprox 62 PSIG Fressue was reduced to 39 PSIG ( page 240 of Volvo service Manual by Robert Bently) Open vacuum line to pressure fuel regulator repaired
When A/C switch is Engaged problem is more pronounced - again stablizes after 60 to 80 seconds.
Run and Idles normal (875 RPM) when "warmed" up.now with A/C on closer to 1000 RPM
Has Automatic temperature control (CU heater unit) - Temperature control unit does send sigal to LH Jetronic control unit pin 16 and the RPM WHEN WARM stablized to aprox. 1000 RPM

Cleaned Idle control valve and throttle body (cleared passage way with compressed air)

Idle control maintains Idle after first warm up

Fuel pressure much too high, should be down around 32 or so.
Is throttle valve clean and idle switch working?
Idle should be at 700 rpm, has someone been messing with the base idle adjustment (the black knob)? Base idle is set to 500 rpm then IAC holds it at 700 and (900 when AC is turned on). After a coldstart should be at around 1200 for a short time. Sure that IAC is working?
There are 2 temp sensors, assume you changed the one for the ECU and not the guage. I did not know that either has a gasket.

--
David Hunter

Have you clean the Idle control valve? In the FAQs.
--
Post Back. That's whats makes this forum work.