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Old 12-12-2018, 07:37 PM   #1 (permalink)
stefanv
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Join Date: Jun 2017
Location: Ontario, Canada
Posts: 85

2001 Saturn - '01 Saturn SL1
90 day: 41.68 mpg (US)
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Annoying Saturn ECU Behaviour

I haven't posted in a while, but the contest announcement has inspired me to do so. :-)

For those who've followed my 2001 Saturn Mod thread, you know that I've installed kill and restart buttons. The restart button is for convenient restarts at lights (at speed, I use the clutch partial-release, press, release technique another poster suggested for smooth restarts with minimal wear).

Anyway, to get to the point, one problem I've had ever since installing the kill switch is that after using it for a day or so, the ECU starts to get the idea that the car is prone to stalling. What it does to compensate is keep the idle high, sometimes very high. I can be driving along at say 1800 rpm, and when I release the gas and push in the clutch to shift up or down, the engine revs up to 2500 or so. This works out reasonably well when downshifting, but it's annoying when upshifting.

I spent a long time scratching my head, reading various Saturn forums, replacing my TPS (although the readings I'm getting from Torque suggest all sensors are working properly), all to no avail. As a software guy, I finally realized the problem is a bug, or rather an unintended consequence of making the engine operate in a way the ECU designers didn't account for.

If I stop using the kill switch for a day or so, the problem goes away, as the ECU relearns that the engine is fine.

Has anyone else seen issues like this? Found any solutions?

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Stefan Vorkoetter: Programmer, hobbyist, amateur watchmaker, pilot, and collector of fountain pens, slide rules, calculators, and watches.

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