I subscribed to the AUTOTAP newsletter because I thought there might be a gem here and there... well the last one certainly was! Or rather a headscratcher: QUOTE "Recently the check engine light came on my neighbor's Windstar and the car did not idle properly. The RPM reading was about 500RPM at idle. The engine idled so rough that the accelerator had to be pressed slightly to prevent the engine from dying. While driving, we also heard some mysterious whistling sounds but could not locate its origin. The whistling sound is more pronounced when the engine is running under load. At 60mph the car ran well, but stop or slow for a turn and the engine would die unless we punch the accelerator.
When we first performed the diagnostic test with AutoTap we found error codes from two oxygen sensors, namely P0171 System too Lean Bank 1 and P0174 System too Lean Bank 2 implying lean fuel mixture. We believe the source of our problem could be caused by a vacuum leak, however we are aware of other issues that could cause a lean mixture, such a faulty gas filter, and plugged injectors.
We tried using several methods to locate vacuum leaks - .... The mechanic quickly found the problem to be the Idle Air Control Valve. Apparently the valve was stuck shut all the time because of carbon deposits on the rod which connected to the valve.
.....
Looking back on our troubleshooting procedures, the cause of the problem is obvious. The Idle Air Control Valve should have been the first sensor/actuator to focus our attention on. The actuator is very accessible and easy to experiment with. The reason we did not focus on that valve was because we didn't know it existed or what it did!" UNQUOTE
So... let me get this straight.. the guy buys an autotap diagnostic tool, but doesnt know that there's such a thing as an IAC.. and, further, what it does?
What's more... the fact that the IAC is to blame for the 'lean condition'?!!!
- The guy should spend the time to study up on modern FI
- I think he needs to clean his MAF as well.