Why Rough Idle ??????

I have a 1998 ford escort se,4 cyl 2.0 duratec eng.automatic .Whenever car is stopped at a light and the A/c or heat is turned on,i get an extremely rough idle ,turn them off and the rough idle goes away ,never
get any error or trouble codes to read.Any ideas why the rough idle.???????????????
THANX
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Probably just the extra load on the engine at low rpm.My 95 escort with the 1.9 has never had a smooth idle.I find putting in neutral makes a big difference.
Bill wrote:

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