Hey guys, I have a 2005 TL Base. The car has 156,739 miles. I recently had a newer engine put in due to orgional engine issues.
The new engine has 87k miles and every belt that moves was replaced, water pump, timing belt.. everything. Flawless engine. (K&N CAI) otherwise stock.
Had my transmission Re-Built with a brand new shift kit put in and everything, fluid changed.. etc.
Recently I have been having issues where it will go from insanely responsive acceleration to drag butt slow. Mainly happens on a hot day after driving a while. I've tried adding more coolant but I will not adjust T-Stat as I've been told that might create a bigger problem.

someone mentioned an "oil cooler, (B&M tranny cooler type thing) I was wondering if this $92.00 part night fix my problems as I've been told my problem is called "heat soak in the tranny" 5AT btw.
Thank you, appreciate any help.

 

how old is your battery?

 

What you are experiencing is heat soak of the engine. Once the engine gets hot, the in coming air the engine burns, heats up and the ECU retards timing which reduces power. There is no real way around this and it will go away during the winter and other cooler months.

 

I have ordered an oil cooler, from B&M. will this fix part of the issue?

 

I had about idea about a solution to heat soak on these engines and that was run a dual thermostat setup that's controlled by a ball-valve that can be switched between hot and cool seasons. The thermostats could be plumbed in parallel and the valve simply adjusted to the low temp thermostat in summer and the stock thermostat in winter. I run a low temp stat in my car and see 200* and below in 100*+ days. This means it will stay hot enough to keep the stock ecm happy and operate in close loop. Makes a HUGE difference in regards to heat soak and maintaining that crispy, cool engine power that we all adore so much.


Just an idea...

 

It's not an issue of the engine running hotter during the summer, the thermostat keeps the engine at about the same temp regardless of outside temp, it's the air the engine is injesting because it's hotter during summer time that results in power loss. One thing I can suggest that is cheap/free and very easy to do is the coolant by pass for the Throttle body. The TL runs 200 degree coolant thru the TB that heats up the air intake sensor making the car think it's injesting hotter air than it is. The air going into the engine is not heated by the coolant in the TB ,but the sensor gets heat soaked and thinks it's taking in hotter air and retards timing while leaning out the fuel mixture to compensate for the lack of oxygen in the hotter air. Relocating the air intake temp sensor is another possible solution. I have removed the plastic piece under the windshield to allow air to flow more freely across the radiator and engine, this is more extream than most want to get, but with the turbo it's very helpful to deal with the extra heat.