Rough engine Idle

Hi,

Either of the things you mentioned can cause an issue. However, there are others. Have you checked fuel pump pressure? Have you checked for engine vacuum leaks? Is the check engine light staying on when the engine is running? If you have access to a live data scanner, can you check the engine coolant temp reading (ECT)? The ECT can send a wrong signal to the computer causing it to make fuel mixtures too rich or lean.

Here are a few links you may find helpful:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Here are a couple links related to the IAC. One is to service the unit and the other shows in general how one is replaced.

https://www.2carpros.com/articles/idle-air-control-valve-service

https://www.2carpros.com/articles/how-to-replace-an-idle-speed-control-motor-iac

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The idea that the problem only exists for a short period of time pushes me to think sensor such as the ECT I mentioned. The IAC and EGR usually won't change and both are likely to cause the check engine light to stay on. If that is the case, scan the computer for codes and let me know what they are.

Here is one more link that explains how to identify the cause of a stall at idle. You vehicle doesn't stall, but the idle is low at times, so check through this and let me know if it helps.

https://www.2carpros.com/articles/stall-at-idle

Let me know if any of this helps or if you have other questions.

Take care,
Joe