Unintended Deceleration

[alanpage@connix.com (Alan D. Page)]

Hello,

I had a strange thing occur yesterday while traveling from a business
meeting back to the office in my 1990 80q. After driving about 15 minutes
between 65 and 80 mph in fifth gear, I encountered heavy traffic and had to
slow down and shift down to fourth then third. As I went to third the car
REALLY decelerated quickly (almost like I'd gone to second). I shifted back
up, and then down again to find that the engine wouldn't go above 3500 rpm.
Any attempt to rev higher while in gear resulted in the car bucking fairly
violently (remember learning to drive stick?...this is scary at 60 mph!). A
quick check of coolant temp, oil temp, oil pressure, fuel, etc. revealed
nothing out of the ordinary. Under 3500 rpm, the car accelerated and drove
normally.

By the time I arrived at the office two minutes later the condition was
gone!? Any ideas? The car has 134K miles on it and the service is up to date
(tuned 10 months ago).

Thanks in advance for any pointers,

Alan Page
1990 80q
Sandy Hook, CT USA
alanpage@connix.com