Idle troubles

[turboberserker]

Hey guys,

I have a 408 with a 236/230 .600/.600 115lsa. I am running a 2 bar tune and am having some strange idle issues that *seem* to be heat induced.

I had major surging going on at stopped idle (in gear, A/C on) of like 300-400 rpm. I adjusted my IAC parked table for the IAT in question (the heat had caused my IATs to be closer to the 104*F cell than the one below which is why it showed up as summer hit) and now have very intermittant and *slight* surging when stopped, but even more annoyingly, I noticed the truck no longer idles at the desired rpm, but 100-200rpm higher (idle is set at 850 and hits between 950 and 1040rpms), and moving from gear to neutral or park causes a sruge to 2000rpm. It will do this multiple times. It is also showing a slight surge during moving idle (like deceleration).

I've noticed that vacuum changes follow the surging, which seems to follow spark changes and/or AFR going lean. I'm kind of at a loss on what to try next.

I started out by adjusting the base spark tables to 26* for low kpa and low rpm (0-40kpa, 400-1200 rpms), adjusting the IAC airflow trables by SOTP to eliminate hestitation and stalls, and adjusting the IAP table.

Any suggestions? Also can anyone the IAC parking algorithm so I have a better feel for which tables I should be screwing up ? :)

[Dirk Diggler]

have you fooled around with timing yet. quick check would be to use the bi-di controls

[turboberserker]

Not recently.

I was thinking of turning of the vac / idle spark thing, but can't seem to find it in EFI.

Are you thinking I need more spark in the base tables?

[Dirk Diggler]

try less. my surging was cured by to much timing at idle. how much timing are you seeing at idle

[turboberserker]

I have it set at 26* but it varies with the vac idle spark stuff (range is around 20-30*)

[Dirk Diggler]

my 230/232 110 +0 cam idles best at 18-19* of timing anything over 20 made the car surge and drove me nuts when comming to lights

[turboberserker]

Dayum DD thanks for that advance tip!! I'm at 15* and it runs very very well. We'll see if it lasts :)

I still have a few funny things to work out -- when it starts it now idles at the rpm I set, but after a minute or so, it eeks up to 950s again. Very confused on that, and am wondering if the PCM is trying to boost my rpms to make the clutch fan it was designed for spin faster to cool the tranny more (200*-210* today) or pull more air through the radiator (ECTS 210*)? I have my tune set to aux fans, which by my understanding tells the PCM there is no clutch fan anymore?

I'd also still like the IAC parking algo if anyone understands when it parks and why :)

[Dirk Diggler]

what are your IAC countts looking like? Have you altered the RAF table?

[turboberserker]

What is the RAF Table? IAC Airflow?

[Dirk Diggler]

Its Idle Airflow B4307

[turboberserker]

That's what I though but wanted to be sure. Yes I modified it for the big cam.

Also, it seems like I'm seeing a little bit of off-pedal surging again as I decel. No where near as bad as before -- maybe 50-100 rpms.

[turboberserker]

ttt anymore help on this?

[Dirk Diggler]

what problems are you still having

[turboberserker]

I still have a few funny things to work out -- when it starts it now idles at the rpm I set, but after a minute or so, it eeks up to 950s again. Very confused on that, and am wondering if the PCM is trying to boost my rpms to make the clutch fan it was designed for spin faster to cool the tranny more (200*-210* today) or pull more air through the radiator (ECTS 210*)? I have my tune set to aux fans, which by my understanding tells the PCM there is no clutch fan anymore?

Also, it seems like I'm seeing a little bit of off-pedal surging again as I decel. No where near as bad as before -- maybe 50-100 rpms.