420A Idle surge 1999 Eclipse GS

[Jay2g]

Hello I recently just got a new ECU and my car starts now, but after like 6 seconds of idling the rpm starts to go up fast like if someone was stepping the gas. I'm running out of ideas and I need help figuring out this problem so I can drive it. It is a 1999 Eclipse GS 420a automatic. Thank you.

 

[dwb]

Check for vacuum leaks.

 

[Jay2g]

Check for vacuum leaks.

btw do you know where this hose goes to? All I know it leads to the bottom passenger side to a hard line.

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[BLACK'98DSM]

That's a vacuum line for the evap leak detection pump. Check the 3 way vacuum fitting on the backside of your intake manifold and make sure none of the ports are open.

 

[Jay2g]

That's a vacuum line for the evap leak detection pump. Check the 3 way vacuum fitting on the backside of your intake manifold and make sure none of the ports are open.

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The owner before me had 1 port open (left) and I had put the line coming from the black box underneath the intake manifold into the left port which im not sure if it goes there or not. The hose with the clamp is the one im really confused about which leads all the way into the bottom into some hard lines.

 

[BLACK'98DSM]

That isn't the proper way to connect the vacuum line. I bet it's leaking from there.

 

[Jay2g]

That isn't the proper way to connect the vacuum line. I bet it's leaking from there.

Most likely but as of right now im just trying to see if anyone knows where that hose goes to. I am still learning and finding new things that weren't in its place since the last owner had it sitting for a year and mistreated it.

 

[BLACK'98DSM]

I'll post a vacuum diagram for reference.

Like I said, that hose is for the rearward portion of the evap system. It connects to the the 3 way fitting on the intake manifold, where you jammed that other hose. Your rubber hose is obviously deteriorated and should be replaced.

So answering your original question, the vacuum leak is causing your surging and high revving at idle.

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