Intermittent idle/rough start issue?

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.

1 Reply

JACOBANDNICKOLAS

MECHANIC
108,205 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