An interesting note for those who might not be familiar, Volvo adopted a
drive by wire system in 1999. The motor controlled throttle body was
designed and supplied by Fiat. This has proven to be a major failure
point in Volvos equipped with it. At least one fatality is said to be
caused by it.
The failure can cause stalling, engine fault lights and surges in
acceleration. There was an NHTSA recall for some cars to fix the
problem, but the real issue is the throttle body uses cheap file
potentiometers as feedback, and they start to wear and accumulate dirt
quickly. I've actually done a tear down of one to look into the problem
with an idea for a proper upgrade to hall effect (no contact magnetic)
sensors designed specifically for the job.
You won't hear much about it of course, because Volvo is the "Safety car".
George Richardson
Dave1massey@cs.com wrote:
> In a message dated 9/18/2009 6:10:26 PM Central Daylight Time,
> mkearns2@gmail.com writes:
>
>> There was an article in the San Diego Union Tribune (a rag of a paper
>> btw)
>> from the head of some auto safety organization who insisted that the
>> floor
>> mats were not the real cause. According to him the ignition systems have
>> become so complex that electromagnetic interference can cause these types
>> of
>> occurrences. Since that article came out there have been many accounts
>> from
>> people reporting unexplained short term bursts of acceleration.
>>
>>
> Typical non-technical jounalist, me thinks. EMI causing havoc in the
> ignition system would only cause the engine to misfire and reduce power.
>
> However, IF that car has "Drive-By-Wire,' or a servo actuated throttle, EMI
> could certainly cause the throttle to open without respect to the command
> coming from the gas pedal.
>
> Does this car have Drive-By-Wire?
>
> Dave
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