I've noticed this happening more and more with my car. Especially when having sat for a couple days. Once I get driving and have done so for 10 minutes or so, it goes away for the most part. Sometimes it comes back later in a trip, but most times, after 10-15 mins it totally disappears (My guess is the engine is up to temp)

When I accelerate, the engine seems to "slip" It's especially evident on hard accelerations. The RPM's also decrease by 100-200 RPM's at the same time as the slip. It can do it as much as 5-6 times while in a certain gear. But it's ONLY upon acceleration and it doesn't appear to be upon shifting gears either (I have an automatic transmission). I know the camshaft synchronizer needs to be changed, but would that cause this issue? My guess is that the transmission fluid also needs to be changed, though it looks ok. I bought the car with 51K miles on it in 2008 (It's a 2004 40th Anniv. Ed. model). I've never changed the fluid or the filter in the transmission because I had assumed it was done when I bought the car as IIRC it is supposed to be done every 60-100K miles for an auto trans and I just hit 60K (assuming it was done when the dealer took the car in to sell. I bought it from a Lexus dealership.

Any ideas on what can be causing this?

 

The fluid in the trans is probably as old as the car (18 years). Change it. All fluids have a shelf life and that gets shortened from being used, Even it was replaced in 2008, that's 14 years old! The additives and slip agents are probably wasted.

Dealers never do anything but the bare minimum when flipping a car. Maybe an oil change or air filter change but things like brake fluid, coolant, tranny fluid, differential fluid. Not a chance.

When trouble shooting, KISS (Keep it simple stupid). Start with the easy or obvious stuff. If it goes beyond that, then you do real troubleshooting and don't' just fire the parts cannon.

Chang your fluid and filter.

 

Any recommendations on a transmission filter and fluid brand? Being as this is the first time I will have attempted this, I'd like some wisdom on the type of filter and fluid is best.

 

Motorcraft- no need to get fancy with it.