Rep Power: 182

Hi,

The problem I currently have is that whenever I start on really cold start. Like -20 degree Celsius, the idle does not go higher than 1500RPM.

I don't have any rough, erratic or excessively low idle (like below 750RPM), it just that before replacing my engine, the idle would go normally at least at 1800RPM, almost reaching 2000RPM.
On cold start, I feel like the engine is suffocating a little bit, like it doesn't get enough air/fuel. It idles and warms up okay.

When replacing my engine, I made sure to transfer all the sensors including thethrottle body and the IACV.
I also have to mention that I cleaned them with throttle body cleaner to remove all the carbon deposit.
I did NOT touch the TPS or the butterfly itself, just cleaned the inside on the throttle body.
I did unscrew the IACV from the TB to clean it and I DID NOT separate the plastic part of the IACV from the housing itself.

Back then, with the old engine, the idle, when starting in warm weather, the idle would go down to around 200-300RPM for like half a second and go back up to normal right after starting. I no longer have that problem now. However, it wasn't that smooth either. When I blip the throttle, the idle would not go back down to 750RPM right away, but it would hang a little while (Like a second) at 1200-1300RPM before going back to normal.

Now, it's a bit worse, it hangs much more long at around 1100RPM for like at least 3 seconds before going back to 750. I also noticed that it doesn't come back down exactly to 750RPM but instead 800-900RPM.

One more thing, I did not replace the IACV gasket/seal but I did replace the throttle body gasket.

Now, could the culprit but the gasket, there is something wrong with the IACV to begin or could it be something external like my alternator that is not performing that great?

Thanks

 
Rep Power: 517

Sounds like what this other guy did, ended up with a similar problem.
I suggest you read this thread, both pages...
https://www.civicforums.com/forums/1...worse-now.html

 
Rep Power: 182

In my case, it also had this hanging issue even way before removing the throttle body and IACV to clean them.

 
Rep Power: 0

I'm the guy from the recommended thread above.

Although cleaning the IACV really well by dissembling and soaking over night in carb cleaner fixed a fluctuating idle issue, I still have the low rpm cold start issue like the OP.

I'm 100% it's the IACV valve. It's just worn out, kinda sticky when cold and needs to be replaced by a new one.