Rom

Hi all,

I'm trying to figure out my cold start & AC idle issues. A few particulars first:

- 2.3L stroked
- ID2000 injectors
- E85 fueling
- stock intake manifold
- Speed density tuned (no MAF, only 4bar MAP)
- Double pumper for fuel

Basically when cold the idle is extremely rough, and AC stalls the car when stopping. I'm not too bothered right now about the cold start (still got some additional tuning to do), but the AC is driving me nuts. Tom tuned the car and when warm, without AC, it's awesome. We have more to do and I know he can fix it, but as we all know he's extremely busy so I wanted to see if there was anything I could do to fix the AC issue in the meantime. It's 100+ degrees out so the car is impossible to drive without AC, so it's getting pretty dangerous to heel and toe at stop lights so it doesn't stall!

The idle hunts when on AC (warm), so it seems like a potential mismatch on the IACV and idle maps, but without AC it's perfect (idles about 1100RPM and is pretty steady and solid, and never stalls or hunts).

I tried messing with the on-AC targets, but I'm not even sure if the latest TephraMOD uses those values.

Anyway, any suggestions would be appreciated!

Thanks,

S.

DatEngnr_Bro

I have this problem, but I just assumed it was a biproduct of my 280 cams & having a small 4cyl engine that has little TQ at that rpm... My tuner told me many of the cars he's seen have this problem.
What cams do you have?

4b11slayer

Have you tried raising target idle woth ac on?

Rom

I do have Kelford 272 cams, though it idles normally without AC, and it's a 2.3L stroker so should have better torque lower down than the stock 2.0L.

I did try that, but I'm not sure if the basic "on A/C" idle params in the latest Tephra do much. Didn't seem to change anything.

I did some logging, and here's what I found:

- Load1B increases from about ~28 in normal idle to between 35 and 40 with AC on
- RPM goes from my normal 1125RPM to fluctuating between 500PM and 1000RPM
- AFR goes from a steady 13.8 to fluctuating between 14 and 16
- Battery voltage goes from a steady 14.2V to fluctuating between 12.7 and 14V (depending on RPM)
- Timing never changes - stays consistently at 15deg on or off AC
- When coming to a sudden stop, about 30-50% of the time, the car will shut off. Load1B during this state is about ~47 at only 300RPM, so the car stalls.

Let me know if anyone has any ideas. A couple questions I have though are:

1) Although the voltage of the battery is dropping low during low RPM, my small battery setup probably can't react quick enough to keep the voltage up a bit. Not sure if that contributes, though if the alternator output is falling due to low RPM, I don't think any battery could keep the voltage up much above 12.7V.. Any opinions on this?

2) Could it be that the ECU is not getting the high/low signal from the AC system to raise the RPM? I saw a mention of the "automatic compressor controller" in the factory repair manual, but anyone have any ideas on where this is, and what ECU pins it connects to? Does evoscan have a mode that tells you if it's detecting this? I'm still researching this one, but if someone knows, that would be great!

Thanks!

S.

Rom

Just a quick follow up. I found the evoscan AC switch on/off status values, but when I run my log, turning AC on or off doesn't register at all! Assuming these values are reading the correct data stream hex values, then that would indicate that the ECU is not getting the signal that the AC compressor clutch is engaged.

I will investigate more..

Thanks!

S.

Rom

Gah, okay, looking at the diagrams, seems that the ECU is the only thing that controls the compressor clutch (pin 20 on connect C-121). That means the ECU has to know it's on, since the A/C does work fine (cold air). The only input I see is pin 83, which gets a signal off the dual pressure switch. This signal comes (via the pressure switch) from the A/C-ECU. I'm assuming that if pin 83 is not active, that the ECU will not switch on the compressor clutch, so the ECU must know that the AC is on.

So I guess my question now is.. should request 49 and 4A have a value of 1 when the AC is on, or are those the wrong request hex codes for AC on a 2006 Evo 9 MR USDM?

Thanks!

S.

Pal215

iTrader: (12)

Brining this back from recent death, but my tuner and I were able to fix this issue just by raising idle using the BISS screw and then he tuned down the idle in the map. Before, I had the BISS bottomed out because my idle was too high after I did some valve cover modifications...extra air entering through the PCV valve at vacuum.