So I recently had my builder install a number of new parts in my 2003 Z06: AFR 215 heads, custom cam 227/231 .61x (both spec'd by Tony Mamo), ported Fast 92 intake, ported LS2 throttle body, ATI balancer, ID injectors, Johnson lifters, chromoly pushrods, Yella Terra rockers, etc. The car makes awesome power but the tuner and I have had issues getting it to run well over time. In particular, the car has random stalls when clutching in and coasting to a stop, especially when you clutch in above the set idle rpm (900). We notice that it gets much worse over time, after setting things in the tune. Last night, the tuner started the car and it ran roughly, he blips the throttle, and it dies. Same thing happens 3 times in a row. So he pulls the tune, and "turns off" the idle relearn process on a hunch (sets it to turn on at 281* coolant temp, off at 282*). Flashes the ECU with the new tune (that was the only change). Car fires right up, maintains a perfect idle. Blips the throttle, and idle falls right in place, no issues. He's going to drive it a few days to make sure the conditions stay good.

Just out of curiosity, has anyone ever had issues like this? How could the idle relearn degrade the tune so badly that the car won't idle under certain circumstances? Is it safe to turn the idle learn off permanently? Me and my tuner are very particular (we don't like to hack - i.e. drill TB plates, hack settings in the tune, etc.). We were just wondering if anyone else has experienced or heard of anything like this regarding the idle relearn process.

Thanks.

 

Interested in what you figure out here....

I'm sure you eliminated the obvious of a vacuum leak? Main cause of idle issues.

My car acted the exact same way as yours with my initial tune, but my tuner was able to correct it. But, I am not positive on what settings in particular he tweaked. I believe mine was just throttle blade % and a little fuel scale tweak.

My symptoms (2000 automatic C5) were:
When I first started the car (cold) it would stumble and some times finally rest on desired rpm on its own. Other times it would die
If I turned the air on it would kill the car at idle
If I took off too soon when I put it in gear it would die.
I sometimes would have to start the car and rev it around and let the throttle out slow to get it to idle.
Sometimes when coming to a stop the idle would bounce and I would have to "save" to prevent it from dying.

To temporarily fix it (kinda) I was able to unhook my PCV and looped the vacuum line on the passenger side between the 2 ports (I think TB and intake) that the PCV went to.

When I looked closely at the passage this allowed a little extra free metered air to pass into the intake with the throttle blade closed - that wasnt crank case air.

Doubt it applies to your situation... But that was my experience.

Your situation with the idle relearn is interesting to say the least.

 

So when he first uploaded the tune it idled OK but over time got worse to the point it wouldn't run?

 

We've probably tried changes and flashed the ECU at least 2 dozen times already, if not more, making tweaks here and there based on other information we've gathered from people with similar issues. After he flashes, it seems "better" for a little bit, but quickly degrades as the idle relearn is taking effect, to the point that the car starts and idles very roughly and if you just blip the throttle it dies. Under normal load, cruising and accel though it's great. It's only on cold starts, and when clutching in and coasting to stops that the issue rears it's ugly head.

 

Seems like the car is learning some incorrect info to me.

Dead spot in the "TPS" in the drive by wire? (theres no actual TPS in these but it does read throttle blade position twice with opposing resistance)

Have you guys ohmed out or checked out all of the sensor readings using his tuner software? (Drivebywire, MAP, IAT, MAF, etc)

 

It's odd, why would the car drive really good for a while and then degrade over time if there is a dead spot or issues with the sensor readings? That is what's been baffling. Everything looks just fine mechanically, electronically, and in the tune and while we are logging the data. We're going to see how the car drives this week with the idle learn process turned off. Wish me luck!

 

what kind of tune are you running?

Closed loop

Open loop

The LS1/6 platform is very hard to work with when you have this issue. It's like we need a missing table to be able to adjust.

here is an old thread on the HP Tuners forum where I was chasing the stalling issue http://www.hptuners.com/forum/showth...nd-idle-swings

and here's another thread where I had an issue with the AC on http://www.hptuners.com/forum/showth...ut-of-the-blue

 

I'd have to ask my tuner that (open/closed). I'm not nearly as versed in this stuff as he is. I've followed your threads on HP Tuners very closely. Our situations are similar, but not exact. The car runs pretty well after he flashes the ECU. A/C on or off, no difference. It's completely random when it starts happening, all different temps, etc. My tuner has tried adjusting the TC, TF, rolling idle, etc. Nothing has fixed it permanently yet. We'll keep grinding away. Thanks...

 

You might be able to find someone near you with HP tuners or EFI live to come by and try to help you figure it out... Might save some money for tuner time. Check out and post on the regional section of the forums.

If you can get some logging/tuning software hooked up and posted some logs on here - someone might see something and be able to point you in the right direction. The guys in these forums are very knowledgeable and willing to help.

I'm interested to hear what exactly your sensors are reading when it starts freaking (watching as it gets worse) and what change the ECU is making that is screwing it up . Also curious what the wideband is saying as this happens. Also out of curiosity - how long is this transition from PCM flash to it "going bad" ?

I am new the the LS1 world so I have no answers - but very interested in the cause/solution.

 

By idle relearn, do you mean the "adaptive idle" section?
There is a whole bunch of stuff to mess with there.
Your cam is small, very much like mine.
Idle shouldn't be too tough to get working, and I say "should" with a grain of salt.

If it works with the items turned off, why not leave it that way?

 

My tuner is also the builder/fabricator who did all the work on the car. He doesn't charge me anything while working on this issue. He uses EFI Live.

It seems to take a few hundred miles before the issues start getting really bad. At first, if I clutched in coming to stops keeping the RPMs under idle (900) when clutching, the car wouldn't die and the RPMs would hold ok. After a few hundred miles, even doing this method of clutching wasn't working. The RPMs would dip too low and I'd have to blip the throttle to save it. Very frustrating. Now it's at the point where just starting the car can be a rough idle, and you just blip it and it dies. Only after he tuned out the idle relearn and reflashed did the car start fine, idle fine, even after blipping. We'll see if it holds... We just don't know why, at this point, the idle relearn may be messing with the tune? We can't think of any other explanations at this point.

 

Yes, I mean adaptive idle. If the car stays running great with it disabled, we will just leave it that way. But like I said, we're both kind of ****, and don't like to "hack" so we'd like to rule out anything else in the mean time before turning off a function of the computer that came from the factory.

 

yep, I turned my adaptive idle off long time ago.

I'm still curious as to what kind of tune you're running. OL or CL

 

Would be helpful if you or him could post a log/tune file.

I had a similar issue that I fixed by enabling rolling idle, following some of printmanjackson's post on the HPTuners forum.

 

Just an update... Turning off adaptive idle has made a HUGE improvement. Along with a few other minor tweaks, the car is finally running well!

 

I have a BAD idle issue that sounds very simular. Going to have to try that.

Thanks

Bill