ECM making up it's own target idle?
#1
Member
Thread Starter
Join Date: Sep 2004
Location: Alberta, Canada
Posts: 231
Likes: 0
Received 0 Likes
on
0 Posts
Car: 80 GMC K35
Engine: TPI 355
Transmission: NV4500
Axle/Gears: 4.10
ECM making up it's own target idle?
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?
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?
#2
Supreme Member
iTrader: (1)
Join Date: Apr 2004
Location: Browns Town
Posts: 3,178
Likes: 0
Received 3 Likes
on
3 Posts
Car: 86 Monte SS (730,$8D,G3,AP,4K,S_V4)
Engine: 406 Hyd Roller 236/242
Transmission: 700R4 HomeBrew, 2.4K stall
Axle/Gears: 3:73 Posi, 7.5 Soon to break
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.
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.
#3
Member
Thread Starter
Join Date: Sep 2004
Location: Alberta, Canada
Posts: 231
Likes: 0
Received 0 Likes
on
0 Posts
Car: 80 GMC K35
Engine: TPI 355
Transmission: NV4500
Axle/Gears: 4.10
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...
So, it should be going to the idle speed I specify, unless there is something else I am missing...
#4
Member
Thread Starter
Join Date: Sep 2004
Location: Alberta, Canada
Posts: 231
Likes: 0
Received 0 Likes
on
0 Posts
Car: 80 GMC K35
Engine: TPI 355
Transmission: NV4500
Axle/Gears: 4.10
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.
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.
#5
Member
Join Date: Mar 2005
Posts: 477
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1988 Corvette
Engine: 5.7L TPI L98
Transmission: 700R4
Axle/Gears: D36 2:59
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.
#6
Member
Thread Starter
Join Date: Sep 2004
Location: Alberta, Canada
Posts: 231
Likes: 0
Received 0 Likes
on
0 Posts
Car: 80 GMC K35
Engine: TPI 355
Transmission: NV4500
Axle/Gears: 4.10
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.
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.
#7
Supreme Member
iTrader: (1)
Join Date: Apr 2004
Location: Browns Town
Posts: 3,178
Likes: 0
Received 3 Likes
on
3 Posts
Car: 86 Monte SS (730,$8D,G3,AP,4K,S_V4)
Engine: 406 Hyd Roller 236/242
Transmission: 700R4 HomeBrew, 2.4K stall
Axle/Gears: 3:73 Posi, 7.5 Soon to break
Originally Posted by 80Sierra
nor do I have a park neutral switch hooked up...
I forget if it is grounded for in gear or opposite.
Trending Topics
#8
Supreme Member
iTrader: (2)
Join Date: Jan 2005
Location: Hurst, Texas
Posts: 9,995
Received 386 Likes
on
329 Posts
Car: 1983 G20 Chevy
Engine: 305 TPI
Transmission: 4L60
Axle/Gears: 14 bolt with 3.07 gears
Originally Posted by JP86SS
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.
I forget if it is grounded for in gear or opposite.
#9
Supreme Member
Join Date: Aug 1999
Location: sweden
Posts: 2,441
Likes: 0
Received 1 Like
on
1 Post
Car: GTA -89
Engine: Blown 415"
Transmission: 4L80E
Axle/Gears: Strange 12-bolt
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 have never seen it in 8D codes but who knows........
/N.
#10
Junior Member
Join Date: Apr 2005
Location: Helsinki, Finland
Posts: 18
Likes: 0
Received 0 Likes
on
0 Posts
Car: Several, all with 8 cyl. Some bigger, some smaller
Engine: Ranging from L8 4,4 liter to over 9,2 liters full aluminum V config.
Transmission: Which one?
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...
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...
#11
Member
Thread Starter
Join Date: Sep 2004
Location: Alberta, Canada
Posts: 231
Likes: 0
Received 0 Likes
on
0 Posts
Car: 80 GMC K35
Engine: TPI 355
Transmission: NV4500
Axle/Gears: 4.10
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.
I'm using a Willem Advanced programmer, with an AT29C256 chip, and Tunerpro to make my BINs. Running off an XP home SP2 machine.
#12
Supreme Member
iTrader: (2)
Join Date: Jul 2003
Location: Dallas, TX area
Posts: 3,205
Likes: 0
Received 0 Likes
on
0 Posts
Car: 91 Formula WS6 (Black, T-Tops)
Engine: 383 MiniRam (529 HP, 519 TQ - DD2K)
Transmission: Built '97 T56, Pro 5.0, CF-DF
Axle/Gears: 4.11 posi Ford 9"
SW = software, as in operating system (WinXP, Win2K, Win98, etc.)
#13
Supreme Member
iTrader: (1)
Join Date: Apr 2004
Location: Browns Town
Posts: 3,178
Likes: 0
Received 3 Likes
on
3 Posts
Car: 86 Monte SS (730,$8D,G3,AP,4K,S_V4)
Engine: 406 Hyd Roller 236/242
Transmission: 700R4 HomeBrew, 2.4K stall
Axle/Gears: 3:73 Posi, 7.5 Soon to break
$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.
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.
#15
Supreme Member
iTrader: (1)
Join Date: Apr 2004
Location: Browns Town
Posts: 3,178
Likes: 0
Received 3 Likes
on
3 Posts
Car: 86 Monte SS (730,$8D,G3,AP,4K,S_V4)
Engine: 406 Hyd Roller 236/242
Transmission: 700R4 HomeBrew, 2.4K stall
Axle/Gears: 3:73 Posi, 7.5 Soon to break
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.
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.
Thread
Thread Starter
Forum
Replies
Last Post
theshackle
Tech / General Engine
4
09-17-2020 08:26 AM