94 Truck dilemma

[David A. Cooley]

At 11:36 PM 5/24/99 -0400, you wrote:
>Hi People,

>Customer had just come from muffler shop and had new o2 sensor, y pipe and 
>cat back system installed since previous shop had told him he had a plugged 
>cat.
>Stored data on the scanner of 75 frames prior to engine stumble and 25 after 
>....looked at every frame and compared all data points to see what voltages 
>had moved or even if vss had somehow gone crazy......
>All this and no codes on the scanner (unless you let it idle poorly so long 
>it sets the high map voltage code)

If it's setting a high MAP voltage then the ground to the MAP or the vacuum
line to the MAP is disconnected.  High MAP means no vacuum which means add
fuel to the computer.  Also, I know I have beat this to death, but if the
muffler shop put in a new O2 sensor and it's a Bosch 4 wire heated sensor,
that could be the problem as well...  The bosch 4 wire heated O2 has no
internal ground for the sensor... AC grounds the low side of the sensor to
the shell.  My LeSabre did the exact same thing until I went back to an AC
4 wire heated sensor.
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           David Cooley N5XMT           Internet: N5XMT at bellsouth.net
     Packet: N5XMT at KQ4LO.#INT.NC.USA.NA   T.A.P.R. Member #7068
   Sponges grow in the ocean... Wonder how deep it would be if they didn't?!
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