xodaraP

Hi all,
I have been having problems with my car, in particular a high idle that often surges between 1200-1500, I'm using far too much fuel (150km to a full tank) and getting a lot of unburnt fuel popping out the exhaust. Exhaust smells extremely rich and fuel in the oil confirms the same.

I've tried so far:
New boost sensor since nipple was snapped off on previous one
New vacuum lines
New O2 sensor
Checked fuel pressure, all fine there
Injectors are good
Checked and adjusted TPS
Checked AFM
Compression is good
Car starts easily hot or cold, flooded once or twice since I've had it (about 2 years)

The odd thing is when I release the clutch or turn on the A/C or something, the idle stables out completely. Thought it might be BAC which would explain the idle, but not the high fuel usage.

I am now thinking after reading around on the Australian forums, that it's an FCD issue. One came with the car - a HKS job with a little dial with a heap of different settings on it. Haven't touched that at all for fear of screwing something up.

We get a lot of Jap import's into Australia, so FCDs coming in on them are very common, as are problems with bad wiring, a misadjusted or failed FCD sending the wrong signal to the ECU.

It is unfortunately hardwired into the ECU, so removal is going to be a massive pain in the ***. And I would prefer not to being that I have a good freeflowing exhaust so I'm presuming it's been installed to account for any boost creep from the turbo.

Wondering if anyone knows enough about these things to know what setting it should be on, so I can check and see if it is on the correct setting and adjust it if it's not, or if it's ok if I play around with it and see if anything changes? I don't want to adjust it and have my engine detonate, that wouldn't be fun.

Will post a pic if anyone can help out with it, but it's a little square box about maybe 3 inches (6cm approx) square, silver label with FCD - Fuel Cut Defenser, small HKS logo in the bottom right corner, white dial, blue ring around the dial, I would guess 12 different settings with the arrows one way pointing to Cut and the other way pointing to Normal. I'm guessing it's different voltages it will send to the ECU in place of your normal boost sensor reading.

After reading about the new style HKS FCDs, I see they say you use Setting 2 for an FC, if I had to guess I'd say mine's on number 7? Sorry for the guess work, the dial and notches are very tiny and hard to see today since it was raining all day it was fairly dark :/ Definitely not set on anything I would call Setting 2 though (either second from the left or second from the right).

Anyone have any ideas? Otherwise I'll just yank the thing out and hope for the best, lol.

I don't think it's a blown engine because I've done all the tests for such a thing, and it continues to start up daily, perfectly fine, some smoke out the exhaust but nothing major, drives fine if a little laboured since it's running so rich. Not hard to start hot or cold etc.

Car is a 1988 S4 JDM Turbo, completely stock so far as I'm aware, stock turbo, stock boost level, emissions removed but BAC and AWS remain as does MOP.

Any help appreciated - thanks in advance

-Sean