Once the engine warms up the idle fluctuates from 1100 to 1400. Engine light is on and code 1642 ICV

I have a 92 318i. I just replaced the engine with one out of a 95 318i which had the same engine. Once the engine warms up the idle fluctuates from 1100 to 1400. Engine light is on and code 1642 ICV. Replaced ICV and no help. Replaced o2 no help. Replaced both water temperature sensors no help. Brought to a friend with an OBD1 reader and will not let the reader in giving a 599 error code. Ordered a DME on ebay. Any other help you can give would be appreciated.

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This post was auto-generated based upon a question asked on our tech article page here: Pelican Technical Article: BMW DME Motronic ECU Swap / Repair

[Nick at Pelican Parts]

Check that there are no vacuum leaks. If none are found, check the circuit to the idle control valve. Be sure it is getting the right control voltage and it is not shorted.

- Nick