Re: Repeatedly Running On A Low Tank?

Jun 11, 2008 2 Replies
C


so explain, since the engine is supposed to have a knock sensor, and


> the computer is supposed to adjust the timing accordingly, how can
> "S*IT GAS" cause detonation???

There is a limit to how much the PCM can adjust the timing. In response to "bad" gas or other factors, the PCM will retard the timing (and in some cases adjust other parameters) to try to eliminate the pre-ignition. But it the gas to really bad, or the other factors are excessive, you can still get pre-ignition. I've had it happen myself.


Ed



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H

Yeah, me too. That's why I avoid the 'bargain' gas stations.

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C

Ed - Be carefull of your terminology. Pre-Ignition and Detonation are two very different (although also closely connected) problems. Spark timing has no effect on pre-ignition other than the fact that if you advance the timing far enough, the "pre-ignition" will be after the spark. Pretty hard to do that and still have the engine run reasonably well though. By definition, pre-ignition occurs BEFORE the spark.

Pre-ignition CAN cause detonation, and detonation CAN contribute to pre-ignition, but both CAN occur separately from each other.

The PCM can NOT correct for pre-ignition - only detonation.

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