4th Gear Poster
Join Date: Dec 2011
Location: Kingston, Ontario
93 Mark w/ premature lockup when cold and shudder on decel
I've searched and haven't found much similar to the problem I'm experiencing, so here goes.
93 Mark VIII, 230,000km's, fluid was changed via pan drop and draining t/c, refilled with motorcraft mercon v, installed 96+ dorman pan and 96+ filter about 2 months/5000km's ago.
For the past month or so, and only on a cold start, the torque converter locks prematurely, instead of 'slipping' as it should until warm. This happens immediately after the tranny shifts to 4th gear.
When I decelerate, it feels like t/c shudder, but it's almost as if the car is bucking. Tapping the brake pedal stops the shudder, so the t/c is unlocking when commanded, which is good.
This goes one for about a minute, until the tranny reaches the temp where it would go back into its normal shift schedule.
From there on, the tranny is perfectly normal, shifts fine, doesn't slip, yada yada. The problems don't happen every day, but seem to happen more on cold days, and only on the first start of the day after sitting all night.
The check engine light is NOT on and the fluid still looks nice and clean. And it's at the correct level, idling hot, in park. Note that when I dropped the pan the magnet was really clean, and the fluid was clear and bright red. The lollipop was gone, so the trans has had some service in the past.
Could this be something as simple as a bad tranny oil temp sensor allowing the tranny to go into normal shift schedules prematurely, or is there something worse going on inside?