I did a Jdm 2.0 swap into a 2007 Legacy. Didn't attatch coolant lines running into throttle body. Engine having a problem holdinga  low idle. Do the coolant lines have any effect on idle. What are their purpose. 

OOps make that a 2005 Legaacy not 2007 Legacy.

Edited November 23, 20169 yr by steve56

They are there to prevent icing. When air is pulled through a restriction, to a lower pressure, it expands, and cools. Under certain conditions, moisture in the air will condense and freeze.

 

Possibly also to help reduce stress due to expansion- cool intake on a hot block would be a lot of stress compared to everything at room temperature.

Does it have the electronic throttle body?

Those often idle low for a while until the ECU has a chance to adapt new idle speed settings. One thing you can do is reset the ECU by disconnecting the battery negative for about 30 minutes. When you reconnect it turn the key on wait about 5 seconds then turn it back off. Do that a few times then start the engine and let it idle on its own. Don't touch the throttle at all. Let it idle until it warms up to operating temp. If it stalls at any time just turn the key off and restart. Let it do its thing and learn proper idle settings.

Edited November 23, 20169 yr by Fairtax4me

Highly unlikely to be related to the problem.  i've removed/bypassed them before without issues and the climate here is colder averages and even colder extremes than your area.  

 

you just did an engine swap - pretty normal for a vaccum leak (check the brake booster), sensor or timing issue. 

Does it have the electronic throttle body?

Those often idle low for a while until the ECU has a chance to adapt new idle speed settings..

oh yeah - 2005+ have that issue. 

 

you're still running hte 2007 ECU right, just swapped the engine?

Does it have the electronic throttle body?

Those often idle low for a while until the ECU has a chance to adapt new idle speed settings. One thing you can do is reset the ECU by disconnecting the battery negative for about 30 minutes. When you reconnect it turn the key on wait about 5 seconds then turn it back off. Do that a few times then start the engine and let it idle on its own. Don't touch the throttle at all. Let it idle until it warms up to operating temp. If it stalls at any time just turn the key off and restart. Let it do its thing and learn proper idle settings.

Yes. Its electronic throttle body. Does disconnecting the battery for 30 miutes really reset the ecu. I never understood the resetting of ecu. I thought the ecu program was saved in memory even with the battery disconnected.

oh yeah - 2005+ have that issue. 

 

you're still running hte 2007 ECU right, just swapped the engine?

Yes I just swapped in the engine. Also I posted it as an 07 Legacy by accident. Its acutually an 05 Legacy. Is there a solution to the issue ?

Edited November 23, 20169 yr by steve56