Low idle on startup 84 US
08-14-2014, 12:41 PM
#1
Pro
Thread Starter
Low idle on startup 84 US
I've been having a bit of a problem with low idle on startup for my 84 US auto. It doesn't happen every time, but more often than not when I start the car the idle stays at ~300 RPM for a few seconds. I usually have to give it some gas, and then after 10-15 sec the RPM usually levels out and stays rock solid. There doesn't seem to be much difference whether the car is cold or warm.
For a bit of context, I noticed this problem after I completed an engine out rebuild over the winter due to a blown head gasket. I replaced all of the gaskets and rubber vacuum lines on the top of the engine (fuel lines were done a year or two earlier). The temp 2 sensor was replaced about a year ago as well.
My first thought was that the fuel pump check valve was dying, so I replaced that along with the fuel filter, but that unfortunately didn't effect the startup problem. One other thing that I had to over the winter was cut and splice the wires to the O2 sensor--is it possible that splicing the wrong wires together would cause this problem? Any other ideas which would fit these symptoms?
For a bit of context, I noticed this problem after I completed an engine out rebuild over the winter due to a blown head gasket. I replaced all of the gaskets and rubber vacuum lines on the top of the engine (fuel lines were done a year or two earlier). The temp 2 sensor was replaced about a year ago as well.
My first thought was that the fuel pump check valve was dying, so I replaced that along with the fuel filter, but that unfortunately didn't effect the startup problem. One other thing that I had to over the winter was cut and splice the wires to the O2 sensor--is it possible that splicing the wrong wires together would cause this problem? Any other ideas which would fit these symptoms?
08-17-2014, 12:21 AM
#3
Rennlist Member
The aux air valve usually causes the symptoms you describe.
Remove yours and test it outside of your car by putting it in the freezer for 20 minutes, then remove it and see if you can see through the port.
Then supply power to it and warm up the bi metallic strip inside of it to see if the disc in between the ports rotates and closes the opening.
If it does nothing or is not fully open or fully closing, this is your culprit. You can bend the bimetallic strip a little to make is fully close and open.
If it does nothing, find a good used one or call Mark at 928 international and pick up a used one for $50 since they are no longer available new.
Believe me, I tried searching for one, and even with OEM part numbers, they are no longer available.
Remove yours and test it outside of your car by putting it in the freezer for 20 minutes, then remove it and see if you can see through the port.
Then supply power to it and warm up the bi metallic strip inside of it to see if the disc in between the ports rotates and closes the opening.
If it does nothing or is not fully open or fully closing, this is your culprit. You can bend the bimetallic strip a little to make is fully close and open.
If it does nothing, find a good used one or call Mark at 928 international and pick up a used one for $50 since they are no longer available new.
Believe me, I tried searching for one, and even with OEM part numbers, they are no longer available.
08-17-2014, 09:45 AM
#5
Rennlist Member
If you google "test (or rebuild) aux air valve" you will get many useful sites and images that will help you understand what's going on.