Rough start even rougher idle

Hi and thanks for using 2CarPros.

First, is the check engine light staying on when the engine is running? If it is, you need to scan the computer for diagnostic trouble codes that will help diagnose the problem.

Here is a quick video showing how it is done:

https://youtu.be/b2IJGfImVvw

Now, I realize most people don't own a scanner, but often times a parts store will do it for free or even rent one to you. With that in mind, that should be step one if the light is on.

Next, based on your description, I really question if there is an issue with fuel pressure. This can be the result of low or high pressure. Low pressure is usually the result of a bad pump or plugged fuel filter. If the pressure is too high, a fuel pressure regulator is usually the cause. Here is a link that shows how to check fuel pressure. Often times, if the pressure is too high, you will see black smoke from the exhaust when it starts, so pay attention to that.

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

One more thought is a plugged catalytic converter. Here are a couple links for you to look through. The first one discusses and describes symptoms of a plugged converter. The second one is how to test one. If this is the problem, it should have set the check engine light to come on and it should show up as a P0420 diagnostic code.

https://www.2carpros.com/articles/bad-catalytic-converter-symptoms

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

If you can think of any other symptoms that may help, let me know. The things I identified seem to be most likely based on your description, but there are other things that can cause the problem.

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

Take care,

Joe