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post #1 of 4 (permalink) Old 02-14-2007, 11:16 AM Thread Starter
Join Date: Dec 2006
Posts: 3
rough idle

1994 T Bird, 3.8 Auto.
I have been working on a rough idle, at all times. I was about to injector replacement. I decided to give diagnostics one more try. I did have a code 181 and 189. New O2 sensors have been installed.
I found the timing was at 15 degrees advanced, so I reset it to 10 degrees, with the spout removed.
Long story short, it idles smooth as silk. So why did 5 degrees advance make such a difference?
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post #2 of 4 (permalink) Old 02-14-2007, 09:00 PM
Join Date: Dec 2006
Posts: 109

Because the spark plug is firing at the wrong time which means the combustion cycle is off, putting alot pressure trying to force the piston down when it wants to come up. Thats why it idles rough because all of the pistons will experience this.

Last edited by scotteiboi; 02-15-2007 at 01:17 AM.
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post #3 of 4 (permalink) Old 02-23-2007, 02:31 PM
Join Date: Oct 2004
Posts: 105
I thought for some reason our engines should be like 3 deg retarded? Am I wrong?
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post #4 of 4 (permalink) Old 02-23-2007, 07:22 PM
Join Date: Dec 2006
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In a sense you are right. The SPOUT plug retards the timing after you set the base at 10 degrees BTDC. But as for retarding the base timing 3 degrees, i'm not entirely sure.
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