Hello,

I have a 2000 Mercury Grand Marquis 4.6L V8 with 115,000 miles on it. The intake manifold was recently replaced along with spark plugs, coils, air filter and a coolant flush.

the problem that I have been experiencing is when I hit a bump my thermostat reaches hot and my engine seems to lose acceleration for a few seconds then goes back to normal, this happens all the time on a dirt road. Also today while I was driving it was raining, and as normal there were puddles on the road and now my the car has a hard time shifting into 2nd, its an automatic and there isent grinding or any noise at, from a stand still the RPM's keep going until it shifts. Before today it was shifting beautifully and acceleration was normal but now its sluggish and terrible to drive.

I don't know if this is important but I did check the transmission fluid and it was still pink and full, the previous owner had transmission work done at 68,000 in 2011, the transmission shops broacher didn't specify what was done but had a section circled that said "transmission parts and labor". 

Any help or any direction you can point me into would be greatly appreciated!