Hi

Recently bought a lightly modified 93 FD, and after 60 miles (no hard driving) and a month, at either cold start or hot start, the idle is horrible.

Problem
Here is the video of the problem:
1. The RPM is bouncing.
2. The AFR is bouncing. (And much lower than one month ago).
3. After turning on the A/C (10~20 sec in the video), it became less bouncy, and AFR a bit more stable.

Other than what the video shows, I also notice:
1. On cold start, huge amount of white smoke coming out of the exhaust, and filled my entire garage. Smells like gas.
2. Once warmer, all that is coming out of the exhaust is black smoke, not too much.
3. I checked the PFC, the fuel correction map, basic fuel injection and e.t.c. are all in default value, maybe it doesn't show it, maybe it's wiped out.
4. The AFR is almost always showing 10.0, means super (too) rich. Ain't no idea why that would happen if PFC is in default.

Question
What is most likely the issue(s)?
- Is it vacuum leak? (some subtle hissing from 7~10 seconds in the video)(low vacuum from the AFR gauge, used to be 18 at idle 4 weeks ago, see 0 second in this video: )
- Is it blown apex seal?
- Is it problem with PFC setting?
- Is it due to fuel running too rich?

 

Update:

Clipped the hose connected to MAP sensor and idle issue solved. Same smooth as in the 2nd video.

But it's still running super rich, <= 10 AFR. Will have to see the original tuning file (and see if it's on purpose or error), then debug furthur.

 

If you don’t have one already, you should pick up a datalogit or similar so you can access the power fc via fc-edit software or similar to see how everything’s configured.

long story short, I electrically shorted something while working on my car and it messed up my map sensor settings within the power fc.