Hi all, Ive been having some problems with the rpm's when I come to a stoplight or slowdown. The engine dips down to about 350-400 rpms and then settles back about 550-600 where it should be. In stop and go traffic it bounces with every stop. I read that it may be a bad vacuum line. My question, what vacuum lines do I check and where are they located. (or are there any suggestions) thx

 

Red,

You are correct in guessing that a vacuum leak can cause that kind of problem. However, most smaller vacuum leaks typically cause a HIGHER idle, since they admit additional air (like a throttle that is slightly open) and a leak large enough to cause a drop in RPM will usually be easily detectable by simply listening to the idlig engine. In either case, checking the vacuum lines for damage should be an annual maintenance activity, regardless.
However, if you don't find anything significantly wrong with the vacuum lines, don't be alarmed. The kind of problem you describe is more frequently caused by a dirty throttle body and/or IAC system. Cleaning the TB, IAC air passages, IAC stepper, and resetting the TPS will frequently solve that kind of idle issue. There are a lot of posts with directions for that, and you can find those with a simple search.

 

Agreed Vader, I would check the TPS first, if it needs adjusted, adjust/clean them all while you are at it. IAC, minimum idle speed, TPS, base timing, fuel pressure. They all go hand in hand with your situation. As Vader pointed out, the tech articles are a very good resource to help you understand how and what to adjust. Hope this helps.