I need a second opinion
 

I need help. I have a 2004 RX8. I took my car to the dealer because the cel was on. Also my car started to stall if I was driving on the freeway for about 30-45 mins then came to a quick stop on an exit. If I gradually slow down then stop, I don't have that problem. I suspected that I had a vacuum leak again. They did a diagnostic and told me there were no vacuum leaks and that I need a new engine. I'm not convinced. My engine was replaced in 2012 and it has about 53,000 miles on it. The codes that were read were P0171, P0442, and P0443. 0442 to my knowledge is linked to a vacuum leak, but they said I don't have a vacuum leak. I'm confused and I don't know where else to look for an answer.

0442 and 0443 pertain to the EVAP system. Could be something as simple as your gas cap not on tight or you need a new gas cap. If it's not the gas cap then you'll need a smoke test to pinpoint the problem.


0171 - System too lean. This code along with your description of how the car has been behaving would lead me to check the fuel pump first.


None of these codes would necessarily indicate that you need a new engine. For your own peace of mind, get a rotary specific compression test done. That'll tell you lots about the health of your engine.

+1^
Other than the vacuum codes, mine did the same thing recently, got a CEL for the gross leak, it was a bad fuel pump.
If you have some mechanical aptitude or know someone who does, it's not a hard job.
Getting the retaining ring off & on is the hard part.

++^^

If it has the original fuel pump, that could easily be it. Does it do it with the tank full, or just when below half a tank? But, check gas cap first, that is the cheapest.

It doesn't do it on a full tank.

Fuel Pump then, 90% sure. If I had those symptoms, and the full tank solved the problem, I would replace the fuel pump. The full tank keeps the pump cool. A cool pump is a happy pump.

A hot, weak pump will make it run lean (low pressure) or die.

Now, there could be a weird relationship between the evap system and the pump that I do not know about. But, I would start with the pump. THere are DIYs out there, and forum vendors sell the complete assembly.

Update
 

Thanks for the suggestions; however, my engine has lost some compression :(. Rather than wait for it to fail, I'm going to trade it. I'm not going to replace my engine again.

What was the result of the compression test?Someone here might buy it as a parts car.
Where is the car located?

If I remember right.... 100psi. I'm in Stockbridge, GA.

A proper compression test will have 3 values for each rotor and a RPM value

They are then normalized to 250RPM's at Sea Level Barometric Pressure

If you have 100 PSI across all 6 readings the car should run quite well...

It runs fine to me. But I'm kinda of tired no power steering and not so awesome gas mileage. I feel like I've spent enough on the car fixing things.

Sounds like you need to move on then. Power steering is a well known issue with lots of documented fixes.

Gas mileage....well it is a rotary ;)

Yeah I know and it prevents me from driving where I really want to go. I've done about every know fix except change the rack and I'm just not willing to do that.

Every known fix such as what exactly?