[T3] I'm a bit confused as to why unplugging this IAD temp sensor clears things up.

[William Jahn]

 From what I’ve read vacuum leaks tend to make the system run richer and I imagine this may cause different issues depending on just where they might be. Also it’s seems that this temp sensor unplugged enriches the mixture this is also what rennlist states as an old mechanics trick. 

 Thing is if any vacuum leak causes a richer mix it seems to reason it’s running lean yet I’ve also read conflicting info that vacuum leaks can cause it to run lean as well , which makes no sense to me. I’ve tested the TPS and it reads what it should when it should yet is it possible since I have not had it off for a good long time or have adjusted it, it could be part of the issue or could it simply be since my vacuum advance can is shot and it advances the timing only on a light load which is the condition I get this unsteady RPM from 1,000 RPM to 2,100 RPM then it has a smooth engine speed transition , if I plug that sensor in from 1,000 to 2,100 RPM no load the rpm rise is not steady or smooth . I’ve had old carbed engines with no vacuum advance and they worked fine yet this is not the same thing by a long shot. I realize the vacuum advance is an economy device meaning with less engine load it will advance the timing/spark sooner , wouldn’t this apply to just sitting at ldle when there is no load then trying to bring the RPM’s up that the timing is just to far retarded? AS far as I know on some type 3 years like 72 they retarded the timing with a dual advance unit to cut down on emissions( lean it out)  yet once you gave it some gas the advance would take over . it was only at idle. 

 William

 
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