Josh

iTrader: (9)

Hey Guys,

I've tried everything I know to try and I still can't get my car to idle smoothly. It idles fine when I start it and just let it sit there, but as soon as I hit the gas it continuously surges to around 1400 RPM then back down to 500.

Here's what I've done so far...

1. Adjust throttle blade until IAC counts are around 30-40 and reset TPS.
2. Shift IAC table to the right until Idle Desired Airflow is higher than Dynamic Airflow.
3. Use the HP Tuners histogram to adjust the RAF. Twice.

My VE table and MAF were tuned with a wideband and the car is running in open loop with the MAF.

I've used the VCM controls to add and reduce spark, but neither seemed to have much effect. I also disabled the Spark Idle Control using the VCM controls and it had no effect either.

Significant mods are AFR heads, 228/232 110 LSA cam, and a ported FAST 90 with a NW 90mm TB. The car is an M6.

I'm at a loss and would really appreciate your input.

Thanks,
Josh

MY99TAWS6

iTrader: (3)

This is just a thought and I just got hptuners and really haven't studied it much yet but can't you simply crank up target idle speed a few hundred. In my 97 talon with race cams I could get it to idle like a baby by just going up a few hundred rpm.And it had surging and all I did was take out a few degrees of timing under the rpms where it was surging. Simple as pie. But hptuners looks a lot more complex.That can be a good and bad thing. I have pretty crappy idle with my setup right now one reason bought hp tuners.
I have fast 90/nw90 and b1 cam 221/221/558/558/114 lsa.Don't want to have to drill hole in my throttlebody if can do it with tuning. Also have a screw on my nw to adjust blade opening.
But first thing I will try is crank up idle speed.

MY99TAWS6

iTrader: (3)

Oh to be clear my gt7 is not installed yet. It might go into stock motor and it might go into 408 or 427. Sure it will idle like huge baby in those.

RedHardSupra

iTrader: (1)

what's your MAP, RPM and VE and spark values at cells where you want it to idle?
is it stable at any conditions, as in any particular temperatures or rpm or anything?

you can pretty much ignore WB at idle with a cam that big, it's gonna be way off. tune with your nose

DaddySS

Did you look at the idle sticky, check you high octane vs base timing table?

SSpdDmon

iTrader: (10)

Personally, I think increasing the base timing is a myth. My 232/238 cam idles just fine in my M6 with 22*~22.5* of timing as a starting point. Increasing base timing in an M6 is a great way to ADD to the surging problem on decel common in cam'd cars. Not to mention, higher timing in the high/low octane tables for low rpm and low-to-moderate cylinder air mass cells is a good way to make your knock sensors go crazy. My experience shows bigger cams actually like less fuel down low and therefore require less timing to burn the smaller charge during lower rpm driving situations. Setting up the idle spark controls and IAC idle controls correctly is the way you want to tackle idle problems once the RAFIG process has been completed.

P Mack

iTrader: (6)

Is your tps reading 0 at idle? Are your stit and ltit close to 0 if you log them them from a cold start until its warmed up? Do you have stall saver enabled? Have you messed with the throttle follower tables at all?

Josh

iTrader: (9)

Thanks for all of the responses. I've attached my current tune and a log that I just completed from start-up to operating temperature without touching the gas.

The TPS is at 0, both the STIT and LTIT are close to 0, and the spark ranges from 23 to 27. I haven't noticed any real pattern, it just seems to do this all of the time.

Please take a look at the log and tune and let me know if you have any suggestions.

Thanks much,
Josh

http://www.joshwhite.info/tuning/idle_6-10-07.hpl
http://www.joshwhite.info/tuning/idle_6-10-07.hpt

P Mack

iTrader: (6)

Can you use attach it as an ls1tech attachment? That site makes you install software to download it.

Josh

iTrader: (9)

Sorry about that, I didn't realize it asked you to install software. I originally tried to attach it but it wanted to open in the browser. Hopefully you guys will have better luck with it than I did.

Thanks again,
Josh

Slowhawk

iTrader: (12)

Some cars are just a bitch and don't tune well like other's. I have found this a while ago that some 90mm TB's IAC ports are too damn small.Port them out and the hanging idle/idle dropping goes away. Idle timing seams to have little affect but the idle timing swing can make a big difference.

P Mack

iTrader: (6)

Try making your idle spark in drive table look like this and see if it makes a difference.

Josh

iTrader: (9)

Thanks, P Mack, I'll give that a try and see how it does.

If the tune and log files weren't accessible before, please use the following the links.

http://www.joshwhite.info/tuning/idle_6-10-07.hpl
http://www.joshwhite.info/tuning/idle_6-10-07.hpt

Josh

My90Iroc

iTrader: (26)

Some things that worked for me when I had similar problems were leaning out the 400 rpm cells of the ve table. Even though you never hit 400rpm those cells affect everything between 400 and 800. If they're rich and your idle drops it magnifies the surging.
I also run real low timing, 16 degrees because that's what the setup liked in order to stabilize the idle. Make sure when you're changing the idle timing you're doing so in the Idle timing tables, not the main spark tables. Also shift your over/under speed correction tables left and right to see how they help the idle searching. I actually tightened mine up and that seemed to help the car find idle a little quicker.

I actually have thought about what slowhawk said regarding the iac ports being too small. I'm glad he said that so now I may port mine just to help with the iac correction for idle.

Josh

iTrader: (9)

I played around with my tune some today to try out some of the suggestions that have been made. I first tried increasing the idle timing, but that didn't seem to help matters, so then I knocked it way down to 14 degrees and it idled incredibly smooth.

I was excited until I drove the car and pulled back into the driveway, at which point it started surging again, though not quite as badly as it been before. Why would it idle fine until I actually drive it?

I've attached an image of what my spark table looks like now. Should I smooth the transition?

Thanks,
Josh

Josh

iTrader: (9)

New post didn't seem to show up on the forum index, so I wanted to bring it up.

Josh

nikon1999

iTrader: (22)

yes thats a big transition.. in terms of surging when your coming down from a stop, whats your throttle cracker look like? ...also stated have you checked your tps reading? did you drill a hole in the throttle blade at all which would affect the raf...just some thoughts

Josh

iTrader: (9)

The throttle cracker is zeroed out and the TPS reads 0 when it's closed. There isn't a hole in the TB, so there shouldn't be anything there to throw the RAF off.

Thanks,
Josh

P Mack

iTrader: (6)

I've found the important thing about timing is not whether it's high or low, it's important to have the spark decrease with increased rpms around idle so it counteracts surging on its own. It reacts much faster than the IAC. The other important thing is when you change your idle spark table, you also have to change the main spark tables to match, otherwise your idle will change as you let off the throttle to come to a stop. Here's what my idle spark looks like right now and my idle is rock solid at 750.

SSpdDmon

iTrader: (10)

The IAC is pretty quick. I use my throttle cracker in the same manner you use your base timing table. My 1000rpm & 1600rpm cells are zero'd out for every mph. My 400rpm cells are ~1.5grams/second for every mph.

The key with idle on cam'd cars (which I've said numerous times) is to limit IAC influence for the first 20~40 of rpm delta (above/below desired). There are two tables that you can tweak to help the IAC at idle - direct airflow correction and learned airflow correction (should be in idle learning section). If you zero out the the 0 & 20 rpm cells in the learning table and the 0/20/40 rpm cells in the direct, then it should help quite a bit. Also, download an '01/'02 M6 f-body tune and look at the idle spark correctors for when idle is high/low. They are a lot less aggressive than the pre-'01 cars. Might be a good area to tweak on your car. Just becareful as the rpms are scaled differently. While looking at the low idle spark correction, make sure it doesn't just drop off after 300rpms. Once mine hits ~8*, I level it off the rest of the way across. Otherwise, it just 'gives up' if rpms get too low.