Hard start, cold start problem, rough idle...now Idle Switch/MAF code

[Kenneth Keith]

Kneale Brownson <kneale at coslink.net> wrote:
>
> Just for curiosity's sake:
>
> On the V8, the engine speed sensor has a history of failing with age.  It
> sits under the driver side exhaust manifold, supposedly protected by a heat
> shield.  When it starts to fail, the car will not restart when hot.  Will
> start cold and run OK cold/hot, but shut it off and try to restart a few
> minutes later and there is no go.  I'm guessing the ECU needs signal from
> the sensor to let the ignition spark.
>
> Has anyone ever found an engine speed sensor go bad on an I-5 engine?
> Could that device cause poor idling on an I-5, but not necessarily no start?

Yes, my buddy's '89 200q10v had an RPM switch go bad, which would make
the car die when hot.  We put another used one in and it is okay now.
I had never heard of that failing until this incident, but another
person pointed us in that direction claiming it's a common failure.
Upon describing the symptoms, he went straight to that diagnosis.
It's simple enough to check if you have another sensor to try.

Cheers,

Ken