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Hey guys new to forum. Have a 01 Civic 1.7 automatic. Just did a JDM engine swap. Now car idles rough when cold. It will start just fine and idle fine. Then like 30 seconds or so goes into a rough idle like its starving for fuel. Try to give it gas it will come out of it but only if your easy on giving it gas. Once temp comes off cold mark on gauge it idles fine and continues to until it sits and cools down. Did relearn and didn't help with the issue. Car drives great no issues no check engine light! Been searching all over looking for the answer. Have tried all the tips on forum. Any advice is greatly appreciated!

 
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new engine in means first thing to check is vacuum leaks

 
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One of first things checked for. There is no idle issue or driveability issues once car is warmed up.