Problem: Idle hangs/fluctuates between 950 and 1200 rpm on decelleration (clutch in slowing down) until I come to a stop or below about 10mph. At a stop, idle is PERFECT. Recurring problem ever since heads cam last October. I've been through about 50 different tunes.

Mods in sig.

What I've done:

Timing tables: All tables 26* spark in idle, 25* spark at 1000-1200 rpm non load. I've been as low as 22* and as high as 29*.

Maf- enabled stock, enabled tuned, currently disabled.

VE table- stock, and now tuned

Throttle body- screw set till IAC at 56 at warmed up idle, a/c off

IAC vs. Effective area- stock, then changed till desired and actual air match, now stock again.

Throttle cracker- stock, then decreased by different % at 400-1600. Currently set at zero for 400 and 1000 rpm zones. During log, shows ZERO when idle is hanging.

Throttle follower- Stock, shows ZERO when idle is hanging.

RAF- tuned many times.

The attached log is from this afternoon with as many idle things you can log. Also attached is my current tune. I'm so sick of freakin idle tuning (as anyone would be after 50 tunes). PLEASE HELP!

The only thing I notice from the log is that when the idle is hanging (first half of log) the IAC is a little higher. It could be coincidence, or a result of the higher rpms though.

Also, the hanging is slightly worse with A/C on than with off. I've tried tuning A/C tq, but that seem to fix anything, so it's stock now too. During the log, I turn the a/c on and off at different times. You can tell by the IAC position, it's about 20-30 higher when a/c is on.

LOG and TUNE can be found here: http://www.hptuners.com/forum/showthread.php?t=6120

Of course this isn't the only problem I have with my idle. The other problem is that for the first minute after startup, the idle will dip to 400 rpms when I touch the gas and let off. After the first minute of open loop, no problem like this again (in closed loop). I leaned out my idle and my OLFA table in idle regions by 3%, it seems to have helped slightly, but problem is still there. But, one problem at a time.

 

Have you tried cleaning or replacing you IAC valve...?

 

Nope. What would I clean it with? And where is it exactly?

Wouldn't that cause problems with my idle all over the place, and not just consistently during decelleration? My idle is perfect at a dead stop.

 

Don't know if you have this in HPTuners. If you do, try taking about 15~20% out of the table and see if that helps.

 

what are your IAC counts when you are coasting to a stop?

 

When idle is hanging around 1100- around 100

When idle is hanging around 1000- around 80

When idle isn't hanging- around 60

 

To clean it: CRC MAF Cleaner or CRC QD Electronic Cleaner

It is located on the driver side of the throttle body, it has a 4-wire connector, it is mounted with 2 torx bolts:

I borrowed someone's pic.

If it is carboned up, it can slow down the pintle motion (meaning the pintle won't react as quick to PCM commands).

Edit:
When you take it off, don't lose the o-ring.
You may also want to clean the IAC bore in the throttle body.

 

Cool, thanks. I cleaned it with QD electronics cleaner. We'll see if that helps.

I think it's a tuning issue though. It started as soon as I started tuning the idle for the heads/cam package.

 

Also, what's the "Pintel?" I sprayed the tip on the inside of the IAC thing. It looked like a round black rubber boot or something. Shape/size was the same as the tip of an o2 sensor.

 

It may well be a tuning issue, but it pays to make sure your hardware is good.
You got it, the pintle is the tip that moves in/out on the end of the IAC thing.

 

Try making sure your TPS voltage is between .4 and .6

Also, in your pri/sec VE tables multiply the 400 rpm by .75, the 600 rpm by .75 and the 800 rpm by .85. (this made a marked difference on my setup - I also smoothed these drastic changes into the rest of the VE table... haven't logged it yet.. I will tomorrow)

Adjust your TB set screw so that your IAC is reading in the 50's if you can... mine is actually down in the mid 30's.

I don't have heads, but a Cartek 2X cam and bolt-ons and these are the things that helped me fix my idle issues.

 

IAC cleaned. Didn't help. But eliminated another variable at least.

VE tables leaned out in the 400 to 1200 rpm ranges was one of the first idle tuning things I did. Since then, I tuned the VE table via SD.

IAC reads about 56 during warmed up idle, A/C off. I guess I could try to go a little lower.

TPS voltage, I haven't logged, but I will tomorrow and see where it's at.

 

TPS voltage was .57

I just opened it a touch more to .59. We'll see how it does after the idle relearns. For the first drive around the block, so far I'm having the opposite problem as before. The idle is going down to 700-750, till I come to a stop, then it settles at 850.

If it stays like this, I'll probably re-enable the throttle cracker at 400 and 1000 rpm. But, the fact that it's still fluctuating tells me the "problem" isn't solved, just moved.

 

i would think you would want some thorddle cracker action but just not what comes from gm


BTW im still learning my onw idle probs so that is just a suggestion

 

Best of luck man! My car only has problems when I've got the wheel cranked or something. Hanging between shifts is extremely minor and not bad enough for me to care anymore. It just falls off slower than it did before. Mine was actually running up in rpms between shifts when I had my TPS set too high. (.74) Now it's about .69 and seems to run much better. It should probably be lower though.

The car works good though. Not going to screw with it.

For reference I'm running stock cracker tables. I also boosted timing by 2 degree's in the Idle Spark Advance between 0 - 1200 rpm and 0 - 0.32 g/cyl area's of both In Gear and In Park tables (even though I've got an M6 and In Park shouldn't count).

That might be something else that's helping.