TRSCobra

I've got a 2006 Z06 with heads, cam, and bolt ons and when it's cold and I'm pulling out of my driveway it's very hard to keep the idle from dipping into the 300rpm range or even sometimes stalling after I give it a little gas to get the car moving. It's been doing this for a while on this tune, but I typically let the car warm up for a few minutes and it was fine. Lately it's been doing it at full operating temp, and even stalled out on me in traffic this week. I've attached a few logs of while it was cold and did the issue.

Wondering if my MSD intake bolts are loosening up? I used to retorque them every few months but I've been busy lately and it seems to run fine otherwise.

idlestall2.hpl

idlestall.hpl

BlindSpot

Looking at one of the logs, it appears to be an idle fueling issue. From ECT @ 79* all the way up to 130*, STFTs are fighting up to a 20% overfueling. Everything else - timing, injector flows, MAP, etc, appear to be reacting to the RPM surges and not causing them. So, guessing at an idle fuel warm up adjustment. I don't see a vac leak with a cam, just the opposite. It also could be the O2 sensors are overly sluggish on warmup if they're in LTs, but still impacting idle fueling on warmup.

Posting the tune might give some clues

TRSCobra

Overfueling huh? I've also noticed the AFR being a bit richer than commanded during WOT runs at the track as well, but its been that way for a while now.

Here's the current tune file I'm running: erik-06-c6-z06-235-245-nw102-mf108-tune-4-edit1-5-16.hpt

sevinn

Take some fuel out in your open loop eq tables and I normally delay closed loop to 120*F or so.

BlindSpot

Yeah, and, something else to look at, since you're seeing this condition creep in over time:

What heat range plugs? One, but more like two steps colder is going to give you a rougher cold startup, especially if the plugs are the copper or copper/copper TR6 or TR7's. I've had gaps widen pretty quickly in the copper plugs, and if they're cold too, they could be contributing.

TRSCobra

Thanks! I'm a complete newb with tuning and this software so I'll look into how to go about making those changes.


I'm running Densos IT-22 if I remember it right. They are iridium but equivalent heat range to the tr7. I had some issues with knock and swapped out the TR6IX to see if it would help. No change but I left them in. Since I've had some timing adjustments made and that helped. Maybe I'll put the Tr6 back and see what changes with the idle.

TRSCobra

So a little update:

Found 3 of the plug wires gave varying resistance readings while being bent, replaced the set (oriellys under warranty). New set gives consistent readings. Replaced the IT22'S with a new set of TR6IX gapped to .035", and for the hell of it, I also replaced the 12 year old 42k mile O2 sensors with new OEM units.

No change. Even in closed loop today pulling up to a red light after 50 miles it started bouncing from ~300 rpm-1300rpm and wouldn't stop til I feathered the gas.

I doubt it's tune related since it was never this bad until recently. Also, the car seems to run great at WOT, trapping 133mph at my crappy local track.

Ed@TheVetteDoctors

Quick look but you have your long term fuel trim min/max set to -13 (.87) and +0 (1.0). Will never be able to add fuel. Set to 1.20 (allows 20%).

Will keep looking when I get a chance

Ed M

jbomx363

Whatever he said... he fixed the issue I had which sounds just like what yours is doing.. though mine was an LS3.

Idles great now!

TRSCobra

Well i tried the LTFT min at 1.2 and I'm not sure how much to add to the open loop EQ tables without picking an arbitrary number.

Reading more into this, it seems it could be related to either the throttle follower or idle adaptive spark control (overspeed/underspeed). Any ideas?

TRSCobra

Update: So I increased the airflow final minimum under 2k rpm approximately 20% and it's gone. The idle hangs ever so slightly in certain circumstances, but I can definitely live with it til I re do the entire idle tuning.