Slipping transmission? '95 Park Ave

Our 1995 Park Ave Ultra has developed an intermittent hesitation-surge. I noticed today at about 70 mph on the freeway. It feels like the transmission
slipps a little, then catches. Not really bad, but noticible. Before I take it to the transmission shop, is there anything else that could cause this? There is no change in the RPM or speedometer that I can detect. And it does not happen all the time. Seems to start after driving for perhaps 20 miles.
The car has 102000 miles, and the transmission was last serviced at about 50,000 so it's due for service anyway.
TIA
Ed
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An slight engine misfire under load in o/d can feel like this.

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Thanks, Shep. Any idea what kind of engine failure might cause such a misfire?
BTW, what does overdrive have to do with it?
Ed

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It's not really the overdrive, it's after the TCC is applied. When the TCC is released, the "shudder" from any slight misfire in the engine will be absorbed by the torque converter. Once the TCC is applied, the engine is directly coupled to the transaxle and slight misfires are easily felt.
I think that sounds good.
Steve

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Steve,
What is the TCC?
Also, if you have some ideas about what could cause slight engine misfires I'd like to hear them. Spark plugs? Crank shaft position sensor? ECU?
And what sounds good?
Sorry I'm such a dunce :-)
Thanks.
Ed

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Here's what you should be inspecting to diagnose your "slipping", aka "shudder," condition: spark plugs plug wires ignition coils ignition control module fuel injector(s) vacuum leak egr valve MAP/MAF dirty/burnt/bent valves worn cam oxygen sensor low fuel pressure bad engine mounts CV joints TP sensor cylinder compression contaminated fuel possible computer software update required (which doesn't appear to be required)

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Thanks, Steve. the car's going to the shop tomorrow for oil etc., and I've asked them to start working down the list. They mentioned some of the same things you did.
Ed

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