Hey guys, sorry to be the annoying new guy, but I I'm still trying to learn the ropes as far as tuning my mild 350 TPI up goes.

My problem is that the ECM appears to regularly make up it's own target idle, other than what I've got set in the idle speed vs temp table.

I've found my engine idles best and keeps itself coolest at about 750 rpm, so naturally, I set that number into my idle speed vs temp table. However, when scanning the truck with TunerPro RT, I see that the idle speed it is aiming for is often 900 - 950 RPM. I am aware that the ECM trims the spark advance to meet the desired idle speed, but what does the ECM use to determine the target idle speed other than the table?

 

That table is only for "in gear" idle speed.
A/C will also add steps to the IAC and increase the idle.
I'm still doing some fishing for the park/neutral idle settings myself.
Mines up around 950 at startup usually.
Just havn't had time to play lately.

 

Guess I should mention my truck is a 4x4 3/4 ton with a standard 4 speed tranny. I'm using the AXCN Corvette bin with the AUJP fuel and spark tables. No AC either

So, it should be going to the idle speed I specify, unless there is something else I am missing...

 

Anyone?

I still haven't figured out why the ECM is setting a target idle of 925 - 950 RPM.

I am unable to get my IAC to drop below 45 - 50 counts either. Even if I open the throttle blades right up so the IAC will close.

 

Do you have a at stock chip off hand?? Pop that in. then dignose it. Are you advance in you're timing tables? I had a silly silly idle problem with my car becasue my timing was advanced.

 

I compared my chip's spark and fuel curves with the stock AUJP bin, just to make sure, and they are identical...

Tunerpro RT tells me that the target idle is about 925 - 950 RPM, and that is exactly where the engine sits unless I open the throttle blades way up....

I've gone through my prom multiple times, and I can't find anything that should be affecting the idle on my engine less the temp vs rpm table. Sure, there are other tables in there with regards to IAC adders for in gear vs neutral etc, except they are all set to 0 like in the stock Vette BIN, nor do I have a park neutral switch hooked up...

It may be something else like a stall saver though. My truck is setting a code 43 (thinkin' the knock sensor is no good), and doesn't always run the best. It likes to pop out the exhaust, and occasionaly out the intake with load put on it.

 

might try grounding it to make the Idle RPM Vs Coolant table active (for in gear control) and see if things work better.
I forget if it is grounded for in gear or opposite.

 

No Park/Neutral switch needed if it is a Manual Transmission .BIN

 

Some bins/codes has a special Idle speed when In ALDL mode, Try remove the 10kOhm between A-B on ALDL and see whats happens..........

I have never seen it in 8D codes but who knows........

/N.

 

I faced the same problem few months back.

Did the same things that you have and was puzzled about what the hell is going on.
First the box itself was under suspicion being faulty. No.
Then the Ostrich emulator. No.
Laptop. FAULTY. Damn Bill Gates and his ****... Put in a new operating SW (still B.Gates though) and everything works now.

It pays to verify the sw in emulator versus the RAM...

 

What exactly is an SW?

I'm using a Willem Advanced programmer, with an AT29C256 chip, and Tunerpro to make my BINs. Running off an XP home SP2 machine.

 

SW = software, as in operating system (WinXP, Win2K, Win98, etc.)

 

$8D mask, Address L862E contains an "Adder" to the base idle speed while NOT in drive.
It is an IAC parameter.
I played with this yesterday and got the neutral idle to come down near the in gear idle speed setting.
Setting it for 38 RPM was a nice number rather than the stock 100 that was in there.

 

That's because yours will idle comfortably at 638 rpm....

 

More like 850 or die for the most part in drive
I just hate to idle in neutral at 950-1000 all the time.
Sounds cooler at 850-875 anyway.
Blub...Blub...Blub....
converter is not a slippery as I should have gone.