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This happened twice yesterday, once in the early morning (08:00) & once in the early evening (17:00). Similar conditions & locations for both occurrences. '90 NA 900 (base model), 5 sp, 161k miles.
The first time was after driving for about two hours. There was an extended downhill section on the West (shaded) side of the mountain of about four to six miles. Temp was probably in the mid to high 20s. During this time I had the car in 4th gear & used engine braking to keep the speed around 50-55 mph. As we approached the bottom of the hill, I saw that the tach was showing 0 rpms. Trying to restart the car, I got only strong cranking. I pulled off to the side & checked the engine to make sure nothing had come off (everything looked good). After about 3-4 min it started up & ran fine for the remaining 45 min of the trip.
The second time was after driving for about 20 min. Now we were heading East (in the shade again) into the same valley as the first occurrence earlier in the day. Temp was probably again in the mid to high 20s. This was also an extended downhill, but the slope was more gradual on this side, so I had it in 5th gear to allow engine braking at a similar 50-60 mph. Again, near the bottom of the hill, the tach had dropped to 0 rpms. I pulled over & tried to start the car, but again got only strong cranking. We waited for about 3 min & the car started fine & ran w/o problems for the remaining 2+ hrs of the trip home. There were many more extended downhills on the way back, but no more problems.
The day before, I had pulled the plugs (BCP5ES) & regapped them all to .025. I also checked all the ignition wires (1 coil & 4 plug wires) for proper resistance & they were all in spec to the Bentley manual & slightly lower than the new wires I recently purchased. I ran out of time & didn't get to check the rotor's resistance. There was no corrosion on the coil terminals. Since all of the old wires showed slightly lower resistance, I left them in the car instead of installing the new wires. I know these old wires have at least 4yrs/50k miles on them. Can this be a potential cause of the problem?
My initial thought was fuel pump(s), but I would've expected more problems on the extended uphill sections than on the extended downhill sections. So what else? Throttle body icing under perfect conditions? (Descending into the same valley under similar load & climatic conditions? Air filter is a K&N drop-in.) Ignition problems of some kind? AIC problems? TB gunk? Other ... ?? And why did it start fine after a few minutes & run perfectly after both incidents?
Again, the car drove fine for 2 hrs (mostly uphill) before having a problem, & then again for 2 hrs (mostly downhill) after the second incident.
Thanks for any suggestions.
posted by 216.160.177...
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