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Intermittent idle/rough start issue?

Tiny
TEAGAN5MG
  • MEMBER
  • 2009 HYUNDAI ACCENT
  • 1.6L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 204,000 MILES
I’ve been having some problems with my car. Sometimes it’s hard to start, other times it’s not when it does start. When it is hard to start it’s rough idle and when waiting the idle finally goes back over the half mark when she rough idles it sits under the half mark. When it’s rough and when driving for some periods of time I get two same codes MAP/MAF Throttle Position Correlation and sometimes I get the code Post Catalyst Fuel Trim System Too Lean Bank 1 and also Idle Air Control System.
Those are the three codes that keep coming up whenever I ran on a computer. I’m lost with what to replace and I cannot find a single diagram online.
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Monday, October 17th, 2022 AT 12:00 PM

1 Reply

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,867 POSTS
Hi,

Based on your description, it sounds like you have an engine vacuum leak. If that is the case, it will cause a lean fuel mixture because unmetered air is entering the combustion chamber without the MAP realizing it is happening.

By chance, could you provide the codes you are getting? If I have them, I can see if there are other possible causes. If not, I would suggest starting by checking for leaks.

Here is a link that explains how it's done:

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

Let me know.

Take care,

Joe
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Monday, October 17th, 2022 AT 6:27 PM

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