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Does it happen on a COLD engine only? Or on a warm start, too? Try the simple things first, like cleaning the Idle Air Control (IAC) unit, Throttle Body (TB), Flame Trap, and checking associated vacuum hoses.
At idle (no foot on accelerator pedal), the TB plate should be closed shut, and the the Throttle Position Switch should activate the IAC valve. Air gets to the engine by going thru the main air hose, detours down to the IAC and then up to the intake manifold. When you depress the accelerator, the TB plate open and air goes straight thru to the intake manifold. Over time, the IAC can get full of oily engine blow-by and not operate properly. This is especially true if the flame trap is not cleaned regularly.
What might be happening is this: the IAC valve is not opening/closing properly, not allowing enough air to get thru to the engine, causing it to stall. To compensate, you are depressing the accelerator pedal, opening the TB plate, allowing air into the inake manifold that way. After a minute or two, the crud inside the IAC has softened up enough, and it then starts to regulate idle air properly.
Another possibility is that the Throttle Position Switch on the TB is set wrong, and it's not activating the IAC when the pedal is not pressed... but this should cause idle problems at ALL times, when the engine is warm or cold.
Check the 700/900 FAQ under "Engine Tune and Performance" for more details on IAC and TB symptoms. I hope it's something cheap and easy to fix...
[[ southern fried volvo - 91 244 133k mi ]]
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