TB vacuum leak and LTFT issues - TCCoA Forums
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post #1 of 1 (permalink) Old 03-08-2018, 10:04 PM Thread Starter
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Join Date: Jan 2013
Location: Tampa, FL
Posts: 44
TB vacuum leak and LTFT issues

Two questions together- I've been chasing a long term fuel trim issue on both banks that to me says vacuum leak (graph and data log attached below). After a couple of smoke tests, it appears there are leaks in the throttle body at the butterfly to throttle cable "hole" (bearing?) and from under the TB at the idle air bypass port. Looking at new TBs, I have noticed none of the aftermarket ones have this air bypass. Is it not necessary? Affect idle without it?

Is the fuel trim behavior indicative of something else other than just a vacuum leak? Lean both banks, decreasing with RPMs. Although there is a slight offset between the two banks (2-4%).

1996 Bird, 4.6L, 205k miles, stock. Thanks!
Attached Images
File Type: jpg LTFTgraphMarch8.jpg (165.0 KB, 1 views)
Attached Files
File Type: zip zipExport-2018-03-08_13-16-95.zip (36.2 KB, 3 views)

Trust me. I was almost a doctor once.
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