This is happening after my engine swap. My car is a 98 C5 M6, I blew a head gasket so I just decided to swap out the motor and install a 99 motor. The new motor has 226/230 .569/.571 113LSA cam, Stage 1.5 heads, and the throttle body is ported with a hole drilled into the butterfly. The broken engine had a perfect tune with LS1-Edit. The old engine's cam was 224/224 .571/.571 114LSA.

Car runs great except for idle at complete stop. It will stay at 850 rpm for a little bit then starts swing from 250 rpm to 1500 rpm, up and down, up and down.

Idle will stay 850 rpm while coasting in neutral and when I first start up. But the momment I come to a complete stop, it starts the up and down thing again. So what the heck is wrong with this thing?

I checked for intake and exhaust leaks and found nothing yet... BTW, if I turn on AC. The car idles perfect... I turn off AC, the idle starts bouncing like a yo yo.

The autotap shows LTFT around 15 or so while cruising. And bank 1 is always 1 point or 2 points higher then bank 2.

So I have the following questions:
1. What do you think the problem is?
2. What should I be looking for in Autotap.
3. How do I tune it in LS1-Edit? I just bought it.

Thank you all

 

There are several tables that are different with the A/C on; I'd start looking at how they are different and copy them over. Something like what you describe is common after camming an LS1. Does it do this only when the engine is hot or when cold?

 

This is when engine is hot.

My old cam was 224/224 .571/.571 114
New cam is 226/230 .569/.571 113

The tuning is the same between two cams. I would think that there shouldn't be too much difference between the cams. I've just purchased LS1 edit, which tables I should be looking into?

Also, is my part-throttle LTFT OK? It is hovering over +15%. Need to bring it back down to 0 right?

 

As close to ) or slightly negative will do fine. Any positve LTFT and the computer will dump extra fuel when you hit WOT

 

benelliwang, I had dying at stop issues with my intercooler I made for my truck. To help this, I cracked the throttle blade by turning the little torx screw on the throttlebody open some. Well unknowingly I past the 0.5volts that the PCM reads as no throttle. I went to 0.6volts on the TPS sensor, and when I would come to a light it would idle for about three seconds and then all of a sudden start searching for a new idle -eventually killing itself.
Just a stab here, and since you have a diagnostic program look to make sure at the closed position the Throttle Position Sensor reads 0.5volts and 0% throttle. If it is not it jumps into another table which makes it hunt for idle like I had and what it sounds like you may be seeing.
Good Luck man. Keep us updated (we all learn by updates to problems). Ryan

 

* * *

What are your IACs set at?? What are your RAF Values?

Here is where to look in Edit:
LS1Edit Go to ->Idle and Limiters Tab -> IAC Park.....what are the values at 40*C and up???
LS1EDit -> Idle and Limiters Tab -> Idle Air Idle Air (Running Air Flow or RAF)- what are the values 44*C and above??
Make sure you have driven around enough for the LTFTs to have stabilized (Learned). Then you want them to average between 0 and -7 %.

If they are off +15% then you need to Scale The IFR (Injector Flow Rate Table) by 85%. This tells the PCM that the injectors are 15% smaller than previously. The PCM will increase the Injector Pulsewidth by 15%....and fueling will increase 15%. O2 sensors ,at this point, should see AFR=14.7 and thus no fuel will be added...in theory. Rescan after driving around for awhile and see where your LTFTS are at. If still slightly positive then rescale until slightly negative. How much is "awhile"..somewhere between 25 - 50 miles.

LS1Edit -> Fuel Tab -> IFR Table Scale (multiply) the whole table - Not individual cells.
Hope this helps some. Good Luck.
joel

 

Thank you guys, these posts exactly what I am looking for.

 

keep us posted.
joel

 

Remember guys, this is a vette - it doesn't have an idle air control valve when idle tuning a vette, you still use the same fields in 'edit but the system reacts a bit differently. You might have better luck opening the hole up a little larger if the throttle blade ends up being open too far to keep it idling.

 

A big thing with a Vette is to do an idle relearn..This really helps the Vette set it's idle and keeps the rpm from dropping under the set rpm.

 

BTW this is the setting from LS1-Edit file I got from the tuner:


IAC Park at 40C = 19
IAC Park at 60C = 14
IAC Park at 80C = 10
IAC Park at 100C = 9
IAC Park at 120C = 9
IAC Park at 140C = 9


Idle Air In Gear at 40C = 12.48
Idle Air In Gear at 60C = 10.32
Idle Air In Gear at 80C = 7.68
Idle Air In Gear at 100C = 7.68
Idle Air In Gear at 120C = 7.68
Idle Air In Gear at 140C = 7.68

Idle Air In Neutral at 40C = 0.00
Idle Air In Neutral at 60C = 0.00
Idle Air In Neutral at 80C = 0.00
Idle Air In Neutral at 100C = 0.00
Idle Air In Neutral at 120C = 0.00
Idle Air In Neutral at 140C = 0.00

 

Yep, I agree with Slowhawk ..I'd do an Idle relearn . Your IAC and RAF values seem Okay..Maybe a little low, but it idles fine on start up, so I'd leave them alone for now. Here is the Idle Relearn procedure for a Vette - Automatic and Manual Trans:


Automatic Transmission:
1 Turn off the ignition

2 Restore the PCM battery feed

3 Turn Off the AC controls

4 Set the parking brake and block the drive wheels

5 Start the engine

6 Allow the engine coolant temperature to reach 176 degrees F

7 Shift the transmission selector into the drive range

8 Allow the engine to idle for 5 minutes

9 Turn on the AC controls (Omit for 2000-01 model)

10 Allow the engine to idle for 5 minutes (Omit for 2000-01 model)

11 Shift the transmission selector into Park

12 Allow the engine to idle for 5 minutes (Omit for 2000-01 model)

13 Turn off the AC controls (Omit for 2000-01 model)

14 Allow the engine to idle for 5 minutes

15 Turn off the engine for 15 seconds


Manual Transmission:

1 Turn Off the ignition

2 Restore the PCM battery feed

3 Turn Off the AC controls

4 Set the parking brake and block the drive wheels

5 Transmission in neutral

6 Start the engine

7 Allow the engine coolant temperature to reach 176 degrees F

8 Turn on the AC controls (Omit for 2000-01 model)

9 Allow the engine to idle for 5 minutes (Omit for 2000-01 model)

10 Turn off the AC controls (Omit for 2000-01 model)

11 Allow the engine to idle for 5 minutes

12 Turn off the engine for 15 seconds.
joel

 

I just did all this and it helped a TON
http://www.ls1tuning.com/iboard/index.php?showtopic=9

 

So, for an '00 or an '01, you'd simply start the engine and let it idle for 5 minutes? Then turn off the engine for 15 seconds and it'll be done?

 

Actuall in my 2001 GM service manual it says to wait 30 seconds. Not sure where the 15 sec is from?

Sorry - I've been doing it wrong, all along, because I hadn't checked it! It worked at 15 tho.
joel
HAPPY THANKSGIVING!!!!