Blow Torch

My wifes A4 car has a mid size cam, AFR heads, 92mm intake with LS2TB and all the supporting mods. I tuned it last summer (HPTuner) and the Car is crazy strong and runs well with the exception of an irritating surge when it is first started (more on a cooler morning) It surges up and down at least 600-1000 rpm, which will causes it to shut off sometimes
I have bumped the idle air flow several times, moved the idle timing adjustmet to the stock 2 /-2 and it doesnt seem to affect it. I have been out of Vette/tuning/modding scene over the winter with other projects, and need to get this straightened out before driving season (now)
Thanks

GoatKart

Did you adjust over/under speed idle timing?

Depending on cam size, a lot of times some level of rpm surge is expected+/- 250 rpm, but these tables can add or subtract upwards of 7 degrees of timing, making it notably worse...

Also, looking at your VE and maf... If you have any huge transitions in the idle area, your going to make your problem worse..


Steady idle comes from steady fueling and steady timing advance... If either is bouncing all over, the idle will too...


What is your advance at idle, and are you seeing it look like a mountain chain when you log it? Something like you command 25 and you see it range from 10 to 36 while its idling (pulled numbers out of my butt)...

Try using the logger to control the timing and specify say 25 degrees... see if your idle steadies out gets worse or gets better...

Blow Torch

I adjusted the over \ under back to 2 / -2
I had it in pretty good shape and was able to run the table at 6\ -6 until I installed the FAST intake and LS2. I haven't been able to get it right since then. I have a 90/90 on mine and it is pretty good but has a smaller cam
Need to find some time to do some logging and look for the things you have point ed out.
I thought I could get it out with idle air flow but raising it doesnt help.

C5 Scully

All the way from Cape Town

Like to join the thread as I have had days of the same problem

HPT Pro and alone

402 forged CR11:1
TFS 235 CNC
FAST 102
NW 102
MAF 102

243/256 - 629/629 - 113* I think its close to the spec

Have scan and log files email: elscullard@hotmail.com

Have done the lamda error on the HPT set-up and done the MAF error to with in 0.99 - 0.01%

I have ajdusted the idle air flow from standard and it was spot on with the given frequency and ended up over shooting and actually pushing the Vette and idle is set at 925 rpm then braking to stay at low speed at idle.... and took it back and parked it again....

The rest is fine and the Vette pulls like a

Please any help will do as I am out of ideas for now.... new MAF calc for LS???? sensor and tune file in HPT to compare....?

C5 Scully

Any advice on the subject will be welcome need to drive slow

CTD

Sent you a email.

C5 Scully

email replied

RonSSNova

You are in good hands with CTD.

Ron (AKA Rattle Can)

C5 Scully

thanks

t100driver

Check your intake, might have a leak.

Blow Torch

I sprayed around everything with some carb cleaner and dont get anything
The frustrating part is it only does it completly cold, so I have one shot to try and fix it, and can't test the results until it completly cools agin, usually the next day

moosifer

What is your initial timing at idle? I have no surging issues running around 12 degrees +/- in the over/underspeed tables. You just have to make sure your initial timing is low enough to allow major corrections. I wish I was on my personal computer to give you the exact numbers. However, I am positive that my over/underspeed is aggressive (compared to stock). Plus, low initial timing (10 degrees or so) gives you the old muscle sound and feel with a mild cam.

Blow Torch

Ill have to check my tune (on another computer) but I think the timing at idle is twice that high. It is in the 24-28* in the 600-800rpm and around .08-.24g/cyl.
****After re-reading your post, I see you MAY be refering to 12* in over under. (Im runnng 8* on my car and it sounds good

moosifer

I just double checked my tune and my base idle advance is 13 degrees up to 1200 rpm through .40 g/cyl then 10 degrees up to 1200 rpm between .44 and .48. My under and overspeed tables go as high as +/- 20 degrees at 200 rpm difference. I dont have any surging issues, but I dont have a monster cam either 219/230 114 LSA. Good luck.

edcmat-l1

It's not timing, it's fuel. It's too rich. Reduce your OLEQ table in the cooler columns, corresponding with the MAP pressure the engine idles at.

Blow Torch

Thanks; Will try that as soon as I can? SUggestions on a target AFR?

Moosifer

That sure seems low....