Odd engine problem on a rainy day . . chug, chug, chug,

Konstantin Bogach konstantin.bogach at morganstanley.com
Fri Jan 2 13:16:51 EST 2004

One wire sensors - engine temp sensor and ISV temp sensor - could be a 
problem.  ECU does not read engine temp from MFT.  MFT is used as 
threashold triggers to cut boost and AC in case of overheating.   Temp 
meter on the dash is fed from MFT.


>Went to same store today, afternoon. Sunny dry day, temp was about 45-50.
>One mile drive.
>Started car after it sat for about 10 - 15 minutes.
>Started ok, rough idle . .gas peddle had no effect. Cleared up in about 5 -
>10 seconds. Some hesitation when coming off idle. After a few minutes it
>cleared up . .no more problems.
>I think the Ignition is eliminated as the cause of the problem.
>I'm thinking one of the temperature sensors is telling the CPU that the
>engine is fully warmed up when its not, and I'm getting a lean mixture.
>How many temperature sensors are there? Is the MFT sensor the main one that
>I should be looking at?

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