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Old 11-25-2009, 08:35 PM   #5
fdryer
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Join Date: Jan 2006
Location: NYC
Posts: 43,474
 

2003 L-Series 3.0L Sedan
Default Re: Passlock / Ignition Problems

With the Passlock issue out of the way there will be a sequence of troubleshooting procedures to isolate where a starting problem lies and the ignition switch isn't part of troubleshooting. If the switch allows the ignition system to turn ON and then allow the starter to engage and tutn the engine each and every time, there's nothing wrong with the ignition switch, period. The problem lies beyond the ignition switch - the rest of the EFI system.

The very first part to consider is the ects for model years through 2001. It has the most effect on the overall operation of the engine and does influence how the transmission shifts. If the engine doesn't run just right, how can the transmission shift properly? The ects is one of the most important sensors since it constantly tells the pcm what the engine temperature is; many past posts have all reported poor engine and transmission faults - all traced to this simple coolant sensor costing less than $15. The pcm determines what fuel/air mixture is used based largely on coolant temps along with various sensors. If this coolant sensor sends incorrect signals (usually acting as if the engine was always cold) the pcm continues to run a richer fuel mixture rather than gradually lean fuel mixtures as engine temps rise. Incorrectly detecting coolant temps by a faulty ects then fools the pcm to shift at the wrong time. Most replacements automatically corrects many issues except for other sensor failures that mimic a faulty coolant sensor. The trick is to isolate each sensor based on how it works and the descriptions you post each time something is replaced or tested for. The next logical step after verifying a valid coolant sensor is operating would be (in my opinion) determining the low rpm at start-up when most starts are high idles unless the engine were already warmed up. The coolant sensor helps determine what rpm is needed; cold start/high engine idle and warm running idle (800-900rpm).

Cold starting should result in 1200 rpm, gradually lowering in a few minutes to 800-900 rpm. The idle air control valve (IACV) also plays a role to help adjust this idling speed.

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