I am looking for a possible vacumn leak which might be part of my lean issue. I just spent the better part of an hour looking thru the service manual for a description of all the vacumn lines and where they are located with no luck. Can anybody help?

 

Can you describe your lean issue. Does it have anything to do with seeing 17+AFR's at around 5500rpm?

 

It actually starts leaning about 5100 rpm's. The reason I think I might have a vacumn leak is because about a week ago it started idleing at about 18AFR and that is when it started really leaning out on the top end.

 

you may have a manifold leak,because you did not have this problem until you had everything installed, call me maybe we can fix it. jim

 

i can send you more mani gaskets if ya want to swap them out but i doubt that is the issue. who did the welding on the o2 bung? you sure there are no pin hole leaks at the bung? and/or the downpipe may not be sealed up at its mounting point at the exh manifold. either of those scenarios would cause the issue

 

Well I wanted to post an update. After having the vacumn system smoke tested and the fuel system pressure tested I was able to rule out these and move on. I had not been happy with the exhaust work done on my car so I went to a different shop and had them cut out all the other stuff and redo it. In the process we saw that the bung for my O2 had been welded really crappy and it looked like I might have a pinhole leak. I was worried about rewelding it with the sensor installed so I waited till I got home and sealed around the entire bung with epoxy putty. I just took the car for a drive and suprise suprise the AFR at a Idle was a rock solid 14.7 and driving at steady speeds it held a steady 14.7. The car is also idleing a little better so I am wondering if the proximity to the factory O2 might have been messing with it's readings too. So a word to the wise you get what you pay for and if you cheap out it will probably cost you a lot more in the long run and not to mention give you an enormous headache. now

 

Glad you figured that out! Now for the dyno tune.