My Si engine just got a bottem end rebuild and now it's acting up. I get the code p0505, my idle is around 1500 and will jump to 2000 then back down to 1500 and then back up. Then when I let off the accelerator it just completely cuts off power causing it to be jerky. Any thoughts?

 

Watch "2000 civic Si idle issues" on YouTube

This is when I step on the clutch and what happens when I'm at a stoplight or stopped

 

P0505 - IACV malfunction.

Have you inspected your vehicle to ensure that all vacuum hoses are connected securely, and free of leaks? This is the most common issue from my experience.

 

Here's this diagram for reference.

 

I have not, is this right by the firewall? And just turn the car on and feel for air?

 

No. In this case it might be best to ensure that all vacuum lines are connected first. If they are, double check that they are secure and then spray the vacuum lines down with soapy water and watch for bubbles.

And yes, this would be starting from the Intake manifold, which is located by the fire wall as shown in the diagram.

 

Alright I'll make sure all the clamps are secure then. Spray it with soapy water and turn it on?

 

That is correct, sir! If all checks out, let us know.

 

Alright I'll check it right when I get home!

 

Try to clean the IACV with brake cleaner.

In addition to the diagram given by Electronblue, check the cruise control hoses.

 

Just checked it and it all checks out. No leaks and everything was on securely

 

just to further what everyone else is saying vacuum leaks are a great place to check. but to add to what your post stated. if you had block rebuilt etc i assume the head would have been removed. personally sounds like possibly forgot a gasket/bad gasket if reused etc. throttle body, tps. etc check for air leaks etc around these portions. iacv throwing a code then try to clean etc.

 

I know the gaskets are all brand new. I'll check the throttle body and tps.and air leaks around them

 

ya i am not a hundred percent if anyone can chime in but while you are driving and car is warmed up. once you turn off maybe around 3 or 4 minutes later restart is idle down or still rev hunting. i also have a si and been battling a obd1 to obd2 conversion to try in get back to stock etc. was battling the same thing. was the tps sensor installed correctly. not to question your skill but the simple things is what kills us.

 

How do I know for sure it is installed correctly? My buddy installed it for me but it wouldn't be the first time he did it incorrectly

 

Remove the air intake system. Start engine. Cover the top of the TB with the palm of your hand and hold it there. Are you able to kill the engine?

If so, restart engine. Use you finger to cover the hole inside the TB leading to the IACV. Does covering the hole make the idle speed drop and the idle surging stop?

 

I'll try this tomorrow afternoon. And when I take my intake off I'll be able to see the hole leading to the IACV?

 

Swain,

There will be a hole right beside the Throttle plate on the inside of the TB of which you should be able to cover with your finger.

 

I put my palm over the TB and it almost died but wouldn't, then I put my thumb over the hole leading to IACV and it didn't die, the idle dropped, the surging was still there but just at a lower speed

 

You have a vacuum or intake air leak.

 

I did that and it just lowered my idle speed but I could hear the surging still happen just at a lower speed. I couldn't make the car die by covering the throttle body with my hand though

 

And I check one by spraying break cleaner or carb cleaner on the lines right?

 

Stock B16a2 engine?

Vacuum leak - Start by simply checking for a disconnected vacuum or PCV hose.

Intake air leak - replace the IM and TB gaskets and torque the nuts and bolts to speck.

 

Stock b16a2. I checked already for disconnected vacuum or pcv hoses.

 

Check all vacuum hoses in the diagram below.

If fine, the the IM or TB gaskets may be leaking vacuum.