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[14.1 Grms]

What would cause the engine to run bad when it is cold / warming up?

Poor factory tuning in open-loop mode would be my guess - bad fuel trims and timing.

 

[Lubener]

What would cause the engine to run bad when it is cold / warming up?

There are not many sensors that are used in the calculation of the air/fuel ratio during open loop operation. Marginal fuel pressure can cause issues when cold where additional fuel is needed.