Derf & List,
I recently had a knock sensor installed after my 94 SW2 with 100K miles on
the motor/trans indicated the knock sensor was bad via the code reader and
the symptoms were high rpm's and low power and check engine light on. I have
had this new knock sensor installed and had no more trouble for 1 week but
yesterday on the freeway the rpm's shot up to 4K higher than before and the
speed dropped from 75 to 60 mph and then the temperature doubled and the
check engine light went on. I immediately turned on the heater to cool the
engine down and limped all the way to my mechanic. The mechanic had trouble
with his computer and removed the code on my car. Any ideas as to my trouble
and which is a good code reader for a 94 Saturn SW2 that I can purchase? Is
it possible when my mechanic installed the knock sensor he needed to do
something else after installation or is this a whole new problem?
Thanks Linda
On 4/28/07, derf <derf247@gmail.com> wrote:
>
> Just FYI a knock sensor "listens" for knock (pre-ignition,
> detonation) which is a situation where the fuel/air charge is ignited
> before the optimal time. This causes a big problem because the
> ignition wants to force the piston down and the crank is still pushing
> the piston up. Knock is bad news. In general, the knock sensor tells
> the ECU that the engine is knocking and the ECU then retards the
> timing or richens mixture to compensate.
> Really clever ECUs can have one sensor per cylinder and can deter
> knock on each cylinder individually. If you ever hear knocking or
> "pinging" and your car doesn't immediately deal with it, then you
> should take action to stop the knocking, i.e. stop accelerating or
> whatever. Forced induction can cause higher instances of knock.
> Using higher octane fuel can decrease the chances of knocking.
> Cheers,
> Derf
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