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Old 03-24-2020, 12:24 PM
Tonyfeb14 Tonyfeb14 is offline
Join Date: Feb 2012
Location: Littleton, CO
Posts: 36
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Rough idle near stall, once SAP cuts out in cold weather

My '03 4.4 X5 starts fine in cold weather (below 35F). It fast idles with the Secondary Air Pump running (new SAP). But as soon as the SAP cuts off, about 2 minutes after starting, the idle is very erratic until the engine gets up to operating temperature. It idles at about 500-600 RPM and the throttle doesn't always respond well until the engine temp is near normal operating temperature. A blip of the throttle and the engine can stall. If its too cold, I can get some flashing of the service light as I detect some misfires. Once warm this all clears up.

It seems like it's running too lean as it just comes off the air pump, or the air pump should stay on longer than 2 minutes. But I assume no adjustments are possible?

I am open to ideas as to what is going on. Once it gets to operating temperature it runs great.
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