I recently took my 37 to an auto parts store to see why my check engine light was reading. The code P0505 came back and I was told I needed to replace the throttle body’s, so I did. I bought aftermarket throttle body’s and replaced them, but the car still had the same issue; check engine light, constant limp mode, having a acceleration and deceleration in the idle, and what sounds like trouble to start. I’ve been to my dealer 3 times and they can’t help me, what can I do?

 

Check all of your vacuum hoses for leaks. 99% of the time whenever there are idle surges the issue is a leaking vacuum hose or a fuel delivery issue (rare). The P0505 is merely a performance code that says the ECU is unable to meet and sustain a consistent target idle speed (650 +-50rpm (depending on load)).

You likely did not need to replace the throttle bodies.

Rule #1: NEVER throw parts at a problem without fully identifying the problem.

 

Did you go through the idle air relearn prosses?
are you aftermarket TS stock replacements? Or Oversized?
if Oversized, you'll need to tune the ECM to match

 

Good catch, SkysG37.

+1 for Idle Air Relearn procedure.