05 CTS-V idle issues

[AADrcw]

Alright I'm trying to help a friend straighten out his CTS. I am still learning HP tuners as I go and I have never messed with tuning on a cammed car so bear with me on this.

The car is a 05 LS6 with a T56, He bought it with a cam already installed but shortly after buying the car a lifter failed and it trashed the cam. He ended up pulling out the motor and having the entire thing gone through. It had all new bearings, rings, and gaskets installed along with a Texas Speed MS3 cam (237/242 .603"/.609" 112 LSA). The rest of the motor is stock except long tube catless headers and a K&N intake.

The problem is at idle only when the car is warm, as soon as you start it the RPMS will drop to 250ish and 9/10 times die. If you start it and feather the throttle for 15-45 seconds the car will then idle at 850 with no surging. Its only on startup once warm. On cold start after sitting overnight the car starts just like it should.

The other problem is at idle only it is throwing lean codes and the fuel trims rocket to 25% on both banks which results in it dumping insane amounts of fuel. Once you start moving the trims are almost spot on usually 0 to -1 with the occasional 1 or 2 here and there. even rolling with it in neutral and the RPMS at 850 like it would be idling it is fine, so much so that the trims rolling with it in neutral were 0 every time I checked, As soon as you come to a stop and the speedo reads 0 the trims go straight to 25% again and you can physically hear the engine change tones from all the fuel.

I attached the tune file that is on the car right now, I have not touched it in any way so its exactly as it was when he got it back from the mail order tuner. I have never tuned idle so I don't know where to start, I don't know if the entire idle needs retuned or if something may have been fat fingered and it ends up being a simple fix.

Thanks in advance for any help you can give.

[mowton]

post a log of the event as well. Interested as to how the O2 sensors are behaving. Your issue appears to be in your adaptive idle area. Log LTIT, STIT as well as Dynamic AF, MAF AF, Advance and adaptive idle spark to name a few.

For starters I would pull like 40% out of the 400/800 VE column, 25% out of 1200 column and 10% out of 1600 column.

Thanks,

Ed M

[AADrcw]

Alright, He will be heading over here within the next 45 min so I can grab a log when he gets here. Will the stock config with what you listed added work for a log or would there be anything else I should add?

[mowton]

Alright, He will be heading over here within the next 45 min so I can grab a log when he gets here. Will the stock config with what you listed added work for a log or would there be anything else I should add?

Stock .cfg plus add will be good to start.

Here are a couple of other changes you may need....
Friction Airflow Initial -- subtract 2 from --40 to 133, subtract 3 from 154 to 284
Startup AF Initial -- Add 2 from -40 to 176, subtract 1.5 from 176-212 and subtract .5 from 248 and 284
Base Running Airflow>Idle Airflow -- add 2 to entire table
Stoich - Set to 14.2
Long term fuel trims>LTFT enable>min learn -- reduce 200% to 3%
PE enrichment EQ could be 1.17 across the board
In PE, make hot pedal the same as cold pedal
Idle Adaptive Spark Control>Overspeed -- shift entire table one cell to the right
Idle Adaptive Spark Control>Underspeed -- shift entire table one cell to the left

Thanks

Ed M

[AADrcw]

Alright here are 3 logs without changing anything on the tune yet.

1 is after the car sat for about 15 minutes and then started without giving it any throttle

2 is starting it again only feathering the throttle to keep it running

3 is restarting right after shutting it off, no throttle input to keep it running

Also on the changes you posted, This is a newbie question but when you say subtract 2 from friction airflow initial, all the numbers are 1.XXX and 0.XXX so how would I go about that?

Thanks again for the help, This is really helping me learn all this. I've only messed with tuning bolt on stuff so this is all new to me.

[mowton]

Make sure the units are in g/sec.....will have to check each of the changes

[AADrcw]

Alright we tried your changes and it still is acting the exact same as before. it still tried to die on startup and as soon as it starts to idle right the trims shoot right to 25%. Is it possible that its not in the tune and could be something else causing this?

[mowton]

Please post the latest tune file as well as supporting logs. Is it have a stock Throttle Body? Is it ported? Is there a hole drilled in the TB Throttle plate? A vacuum/air leak will drive trims to positive. Also, let it idle for a longer period of time (couple of minutes) and how does the car drive otherwise?

After the above and based on the findings, we can asses the startup issue again and lets try and tune some of the low level air model stuff using the MAF. Set High RPM disable to 400 and log the LT+ST trims (set up a histogram for this) to see if trims come back in line. could help point to an air leak.

Ed M

[AADrcw]

Alright here is the tune with the adjustments made, The log for that looked identical to the ones posted above (I would post it but I forgot to save that log I can go and get one for you now if that would help). We let it idle for about 10 minutes with that file on it and there was no change, once the idle caught itself and the trims shot to 25% they stayed there. it won't die or surge once it catches itself but it will constantly dump fuel.

He is using the stock throttle body with no hole drilled in it, I just went out and checked to make sure.

What would be the best way to set up a LT + ST histogram?


Thanks, Cody

[AADrcw]

To add this is only happening when sitting still. As soon as you start moving the car runs perfect and the trims are all around 0. Even coasting with the rpms in the same range as idle the trims are right where they should be, As soon as you come to a complete stop they shoot back to 25%.

[mowton]

A longer idle log and log from idle to moving showing the trims returning to 0 would help as well. Could try adding 1.5 g/sec now to the Base running Airflow.

Ed M

[mowton]

To add this is only happening when sitting still. As soon as you start moving the car runs perfect and the trims are all around 0. Even coasting with the rpms in the same range as idle the trims are right where they should be, As soon as you come to a complete stop they shoot back to 25%.

Try these settings for the startup issue.....

AADRcw startup tables.png

Thanks

Ed M

[AADrcw]

Alright Ill make the changes and flash them later this evening when he gets off work to see what those will do. At the same time I'll get some better logs for you.

Thanks again.

[AADrcw]

I was able to get it to start and idle perfectly. It ended up being the overlap from the cam combined with the headers was tricking the o2 sensors into a false lean condition. I ended up using a hybrid OL for idle and CL for eveything else set up to fix it. Once I did that its all good now.

Thanks again for the help

[mowton]

Interesting, that fixed the startup issues as well as the 25% trims at idle? Could you post the final tune and logs so we can see the cause and effects for the memory banks?

Thanks and congrats on getting it sorted out.

Ed M