The very first thing I would try is the ASD relay. (Auto Shutdown Relay)… its in the fuse paneI. It would cause the symptoms you have…and it would happen all of a sudden. Look into it on the net… … Im sure you will see plenty about it. Your comment on the tach needle not moving at all made that pop into my head…
A failing automatic shut down relay will cause the spark plugs to become carbon fouled? I think the oxygen sensor has failed.
No @Nevada_545 they became fouled during the drive time he had on the plugs just prior to the batt dying…and then this new issue becoming the main problem… I think you might be under the impression that these new plugs had zero run time?
The Op stated. The next day, I replaced the spark plugs, which were all blackened even though they were not old, and then it ran ok until the battery went dead a few weeks ago.
I would be all over that ASD… its as simple as checking a fuse, well sort of, just be sure it functions…why not?
P.S… You can also be correct as well in this scenario… I just wanted to mention the ASD…as a failed one would kill ignition suddenly…etc
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That’s simply not true. However, since the 1996 model year, automotive interface has been standardized by OBD2 requirements. That means:
- Things that set fault codes on a modern vehicle may not set codes in yours.
- Scan tool data that is available on a modern vehicle may not be available in yours.
- It may be difficult to find a shop that has maintained a now-obsolete scan tool to access and diagnose your ECM with live data and bi-directional controls. The shop would also need a tech with enough gray hair to know what he is looking at.
With the proper equipment and experience this should be easy to figure out. If the problem is in fact that the engine is overfueling at start up, prove it. Scan tool data will show injector pulse width in milliseconds, a labscope trace at the injector can be recorded and measured to verify. If the injector pw is indeed high, then a step by step test of all sensor inputs and outputs needs to be done. For instance, does the ECM think the temperature is -40* when the problem is happening? Is the MAP sensor reading from the scan tool the same as the reading at the sensor?
But since none of this equipment seems to be available, I think you are at the mercy of replacing parts.
What is the reason for suspecting over fueling? How wet are your plugs? A sleeping ignition coil will cause a fuel smell…and make the plugs wet.
I keep thinking of the mention of the tach not moving…when normally it did move even during crank. That makes me suspect the coils arent firing at all.
Has the OP checked the ASD relay… swap it with an identical one…just for giggles.
I wouldn’t immediately jump to the most severe condition possible here…PCM failure… imho those are rather rare, possible but rare and shouldn’t be the square to jump to so easily. Just saying.
The OP stated so. He said he had it at a shop and that’s what they told him.
Ooops @asemaster there I go again… just breezing past important details. Apologies… you guys gotta keep me in check here. lol