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If the throttle body is acting as the idle control, it may not be the throttle body itself, but the throttle position sensor (tps). I assume that year has one?
The iffy idle can occur like that with a faulty tps because the ecu doesn't know how much to enrich the mixture because it can't "see" where the throttle is positioned so it hunts around trying to find the right mix of throttle position and fuel mix. The ecu tries to do all the adjustments on the fly as it tries to look at the combination of temperature and idle speed. This can be especially critical during warm up/idle as the ecu would not see the throttle as being closed so sends the wrong fuel mix which over enriches, which causes a cutback, which causes a lean mix, which causes an over enrichment, etc., etc., etc....
Just a thought. It could be the throttle body itself though. Have you checked the tps setting? In most cars, it's a matter of just reading the resistance compared to where the throttle is positioned from the stop/closed. Many times tps' wear out because most of the time, like an idle valve, it spends its life in a limited range. There is usually a carbon/resistor track that a wiper sweeps across which determines the resistance. As the wiper sweeps across over and over, the track wears out and, depending on the substrate, the ecu starts to see too much or too little resistance. This is compounded by the fact that a lot of times, because of manufacturing methods or defects, as the track wears out, portions of is will either wear faster, or even "chip" off. This leads to wildly swinging resistance levels as the wiper tracks across the extra worn/chipped portion and then hits a normal portion, etc. You can usually see this by measuring the resistance of the tps and seeing if it swings unusually (down,up,down or up,down,up,) while you move the throttle by hand through its range.
posted by 98.229.227...
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