Quote:
Originally Posted by christofoo
Here are the spark plugs. I lied, they are not all the same. They are ordered 1-4 from left to right. 1 and 2 are the ones I said clearly affected the idle speed, 3 and 4 are the ones I said have only a subtle effect on idle speed.
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After some (more) googling, I found this:
89 corolla idles poorly. - Toyota Nation Forum : Toyota Car and Truck Forums
After running for a few seconds, I pulled off the vacuum line from the AAP to the thermal vacuum switch and found gas in it, almost certainly confirming that I have a fault in the AAP diaphragm leading to flooding of cylinder 1 via the vacuum lines, as described in that post. The presence of gas in that line, combined with the color of the cylinder 1 plug, together seem like smoking gun evidence that the AAP diaphragm was at fault. If there is any alternative explanation, I wouldn't know what it is.
EDIT: I never did have any backfiring, such as other users reported. It may be that my AAP diaphragm rupture had not progressed the point that it could cause backfiring.
So I have disconnected and plugged that vacuum line (eliminating the flooding at the expense of killing the AAP, not that it was probably working before), and although a single 10 mi drive is far from definitive given the subjective nature of the symptoms, I notice: less "misfiring", smoother idle, quicker kill with less tumbling for EOC.
I'm excited about what this might mean for mileage and emissions. I'm due for a tailpipe test in Jan (required in my area). It'll be interesting to see if there is a significant difference.
HOWEVER: I've become suspicious and still am suspicious of my EGR and will be doing some checks on the valve, maybe even open it up and look at the deposit levels, later this week. The one symptom that I think the AAP diaphragm fault doesn't explain is that (I think) I have some pre-detonation when using lower octane gas. Also, with the engine at 223k, I think it's worth a look.