Idle surge

[BOTTLE FED]

I am working on a 99 C5 with H/C (mid size cam) with Fast 92 and LS2 TB
The car runs strong!! I have MAF and VE tables VERY close, and after the car is warm, it runs great.
The problem is this annoying idle surge, especially when it's first started (warm or cold temps) It surges, or "hunts" for the idle speed. I have changed idle timing, idle air flow (up and down) and just can't get this eliminated.
Any suggestions?
Thanks

[MMGT1]

Steady state data used to tune VE and MAF first? Is it doing this when you go MAF-less? How much vac are you seeing at idle, manifold KPA? Log and tune and config is going to help...

[BOTTLE FED]

MAF and VE were tuned pretty close. I unplugged the MAF and it didn't get any better, and maybe a little worse. Vacuum is aro
und 14-16.

[MMGT1]

Timing at idle, what are you running? Mid size cam= 235 duration or so?

[BOTTLE FED]

Cam 226-236 .Timing at idle is around 26*.
When the idle "settles down" I can give it some gas and the rpm will drop so low it almost chokes down. It almost acts like a vacuum leak, but I have sprayed starter fluid everywhere and nothing. It mostly does it cold and warm. After she drives it, the idle is USUALLY ok, but it can still act up. Not sure how much they will affect the idle, but The 02 sensors are EXREMLY lazy, so I am going to put a couple in it as soon as I get a chance.
Driving me nuts!

[MMGT1]

Try this... enable PE mode at 0% TPS and set PE to stoich in the idle region of that table. Fire it up and try live controls. Drive your AFR commanded lean with live until it shudders a bit then back it off until stable. Transfer that error to your VE table and see if it helps... might be worth a try here. You can lower timing, *increasing temps, and should get the O2's to react a little better as well. I know you said you've gone up and down, but down will increase those temps. Try PE at idle first though and see what it does

[MMGT1]

What RPM are you aiming for at idle? 8-850?? If lower than 800, bump it up a bit as well

...and what route did they go to install the LS2 throttle body? Did they use the Caspers harness for it? So, with this engine, they've gone from a 78mm to a 90mm TB? Is 0.0191 the factor in your area scaler now?.... see why I'd like to see the tune bud...lol

[Red01Z]

Are you using Russ K's idle airflow config? It sounds to me like your RAF table is out of whack. Like MMGT1 said, if you post a tune then we don't have to guess on some things.

[BOTTLE FED]

I will try to set up HPTuners on this laptop. My desktop with internet connection crashed a couple months ago, and this is one of my company laptops.
I have idle at 800rpm
I have BRF at 13.75. I have moved up and down and it hasn't changed much
It is a LS2 with a caspers harness.
I have the scaler set at .0255. I tried several settings, and it wouldn't run at any lower setting

[MMGT1]

Then something is messed up somewhere else if you cannot place .0191 in the area table. The value I'm giving you there is what you want. Try to get that tune up when you can, has to be something in there doing this to you
Did you have a chance to try OL at idle? How did it react?

[BOTTLE FED]

HC5coldidle1027.hpt

Here is the latest tune

[BOTTLE FED]

I generally don't have much time to work with it during the week. It's pretty much dark when I get in.
I played with the scaler for quite a while after I installed the intake, and it just wouldn't run with any lower figures.
Thanks for checking out the tune. I'm sure there is a lot of areas that are off. I've done exactly what you shouldn't do when tuning, and that's getting frustrated and trying a little of everything...

[BOTTLE FED]

I tried changing the scaler to the recommended .0191 last night and the car would not stay running (didn't crank well either)

[MMGT1]

Did you log that by chance?

[MMGT1]

After start decay delay.... wondering why that value is so high in mid temp ranges first off here
I'm seeing that you have made the attempt at "lean cruise" as well. Did you scan for what fuel cell you are in before setting that table up? Don't want lean cruise at idle, you want 14.7 at idle. I would leave the idle region of the O2 sensors stock which is in the 450mv range. Try that one out and see what it does.
What % TPS is reported at idle? Like to see your scan at idle to see what your TPS reads at idle. Your proportional idle for CL has me wondering here too but just a guess without a scan
I think you went a little far on the Idle Airflow table as well. Go back to stock and add just 2 g/sec to it. Your in the 4-5 range added right now
This car equipped with headers by chance?

[cesar]

is your OLFA table stock?

if its not, its probably that.

try to aim for .94 afr on cold starts..

[BOTTLE FED]

MM


Im not really sure what you're referring to on the lean cruise set up. Didn't know I had changed anything to do with the O2s. The car was originally tuned by a "tuner" when it had just the cam, so SOME of the things may have been changed earlier

I dropped the entire Idle airflow table by 2, because I have been attempting to correct the problem with it by raising it, and figured I went too far, but it had no effect when I lowered it.

Cesar
What range are you referring to setting at 13.8?

Thanks

[cesar]

MM


Im not really sure what you're referring to on the lean cruise set up. Didn't know I had changed anything to do with the O2s. The car was originally tuned by a "tuner" when it had just the cam, so SOME of the things may have been changed earlier

I dropped the entire Idle airflow table by 2, because I have been attempting to correct the problem with it by raising it, and figured I went too far, but it had no effect when I lowered it.

Cesar
What range are you referring to setting at 13.8?

Thanks

The open loop fuel tab under the fuel section on the top left.. should be map vs ect iirc

[MMGT1]

If you look at your O2 switch points for bank 1 and 2 you will see a value in the 500's there. This is our way of forcing lean cruise where the NB O2's are now using the 5xx as its switch point instead of 450's, meaning leaner fuel in CL while in those fuel cells. With what you have your probably 15.1-15.3AFR. If you set them back to stock, you would be aiming for the "normal" 14.7AFR
The previous tuner had gone for a few extra miles from a tank of gas... actually done right, you can pick up quite a few MPG.

[MMGT1]

...wrong thread!