[T3] 73 squareback auto trans FI question

William Jahn willjahn975 at gmail.com
Tue May 17 10:31:58 PDT 2022

For some odd reason since it's been hot and dry 8% to 15% RH 90 degrees F.
I drove a 12 mile round trip and noticed the idle dropped 200 RPM. It was
always 1,000 in park and 800 in drive.  Then the next day drove it 1 mile
round trip and it was the same.

 I am not certain if it's the fuel the pumps say at least 10% ethanol. The
charging system works fine. It puts out 14 volts above idle meaning if I
place it in neutral @ 1000 RPM it would read 14 volts and while driving at
any speed it is 14 volts read at the battery and the battery even after a 1
mile drive reads 12.5 VDC.

 I thought perhaps since dry weather is less dense that might be the issue
since the MPS does not adjust for this just altitude as far as I know.

 Last time I dealt with this I replaced all the vacuum and fuel lines and
runner hoses and intake gaskets. I got the proper ones from Jim . After all
of this it still had the same idle running issue. The RPM would lag no load
unless I unplugged the IAD temp sensor. So I decided to adjust the MPS 1/4
turn CC richter until it ran smooth with the IAD sensor connected. It's
been fine since I did this. Now the idle issue has cropped up. I haven't
started it in 2 days to see if it's back to normal, hopefully it is. If not
I need to get it hot and either raise the idle 200 RPM or possibly adjust
the MPS a bit richer. The idle screw lock not is tight so it didn't change
by itself. I did install points and they only have 1,100 miles on them and
while driving I don't feel any difference in pickup and they still look new
and the gap hasn't changed.


 I also removed the engine lid and the lid seal was stuck to the lid so I
ordered it from ISP West.
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