I have been haveing an idle issue with my stang, it jumps between 400-650, when i unplug the IAC it dies, and when im at stops, put it in reverse, or turn the wheel at a stop the rpm's drop to like 400, please any help would be great!!!!!
Clean the MAF. Use only cleaner designed for the purpose. This is important.
For low idle concerns, look for vacuum leaks. Especially in the bypass line to the IAC.
Low idle can also be cause by weak ignition. What is the condition of the spark plugs, wires and coil pack?
Finally, If the inside of the IAC is blocked with PCV blow by (from normal) age, it will not pass enough air to maintain the correct idle. Suggest replacing since a great deal of time it is the IAC.
just changed the plugs and wires, where is the bypass line located? it idles for the most part at 650 just when i turn the wheel and somtimes as i slow the rpm's drop really low, aslo sometimes at stops the rpm's will jump and cause the car to lurch forward
Does your power steering pump have an electricial connector on it? Is it connected? Some power steering pumps have a pressure switch to let the PCM know when load increases. This enables the PCM to increase idle to compensate.
Consider changing the IAC just because oftentimes it is the problem especially on older/high mileage cars. Especially the IAC with the black vent.
Have you reveiwed the other items listed?
If your IAC has a 1/2" vent line attached, that is the bypass line. Some IAC's have an internal bypass line. In which case. cleaning/replacing is the only option.
Regarding cleaning. Don't clean the IAC with the black vent. Replace it.
The non-vent can be cleaned. However, 50/50 chance it will be effective. Cleaning is most effective if the problem is clogging due to PCV blow by.
If you still need help, post pictures of your IAC. Also the resutls of everything done and will go from there.
It doesn't sound like you actually read the post. If you had, the post tells you that the black vent provides bypass air for starting. The post states that the black vent version is less likely to die when the electrical line is disconnected. The key thing the basic functional test is looking for is the CHANGE(lower) in RPM's. No change equals no IAC function.
Since you have now confirmed the black vent version, do yourself a favor and buy a new one. The black vent version can not be effectively cleaned.
If you still still wish to test, an ODB2 scanner with the ability to monitor operational parameters will be needed.
Again, as mentioned before, there are multiple reasons for a slow idle. Tests are needed to rule in/out the various causes. Sometimes you just need to start at the most likely place and work from there.
OBTW, should you decide to clean the black vent IAC, please don't post any requests for more help should it not work. Note, I am not going to tell you with absolute certaintaty it won't work because sometimes it does. However, the odds favor the results to be only temporary. Or one set of problems will be traded for another.