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
"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!"
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
What's more... the fact that the IAC is to blame for the 'lean
1. The guy should spend the time to study up on modern FI
2. I think he needs to clean his MAF as well.
Yeh, I'm a Krusty old Geezer, I believe you're never too old to learn...
what stifles that is forgetting what it was you just read.
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