Idle surges and dies. Cam w/ 114 LSA

[RPM-silveradoSS]

I am a novice tuner and am fighting with the idle surge and die. When it surges mostly at parking lot manuvers and staging. I just dont know what to do to correct it. I has done it more so now that it is getting cold. The list of mods is: 6.2L LS3 w/ 24x reluctor, Comp Cam 224/230 dur. .581 in. / 591 ex. @ 114 LSA. Factory 90 mm throdle body fly-by-wire. K & N cold air intake. Factory MAF 03 silverado SS. NGK TR-6's . 3200 stall converter. I got my idle low but even with it up at 800 it still does it. Any Ideas?
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Attachment 15439

[kevmar]

try doing a RAF test "running air flow" at cold in park then the next morning in Drive. May take several times to get it right, after each time drive it for atleast 50 miles and let sit for 12 hours. Good luck.

[SSUte01]

If you are confident that your RAF is good then the most common cause of surging with cammed cars is over fueling. Sometimes you will need to have a 'measured' lean idle to have an actual AFR that you need. I know that sounds confusing but my point is that just because your narrow bands or even most widebands are telling you that it is at or near stoich doesn't mean it that is really happening at combustion. Sometimes you just need find the 'happy' AFR to get at or near happy combustion. For your cam try leaning your fueling out using the scanner to see if that improves things. I have found that a measured 15.5 - 16.0 is often closer to the real stoich on cams with that profile, but having said that each are different but I am fairly confident that due to the cam being less efficient at idle that you are over fueling somewhat.

Also the reason I think over fueling is that this condition is usually exaggerated by cold weather because of the over compensating bias calcs.

To correct you either have to command a leaner AFR and make actual AFR equal commanded or as I prefer command stoich (OL idle is my preference for cammed cars for this very reason) and then if you find that commanded AFR of 16 is 'happy' then go back and mult your VE/MAF (whichever you are using) by (14.63/16 or 0.91)

After all that be aware that your RAF will need re doing for stable idle conditions everywhere as fueling has a large impact on 'desired RAF'. And you may need to do some fudging of OLFA to get the 'real' AFR you are chasing on warm up. These are about the only times where the actual AFR (as you measured it) is different to the commanded AFR, without more complicated equipment I am not and have never been confident that our inexpensive widebands are accurate at idle with cams even a little larger than stock like yours. I am sure many disagree but that is what I have found with various widebands/cams.

Hope you get it sorted

[SSpdDmon]

I am a novice tuner and am fighting with the idle surge and die. When it surges mostly at parking lot manuvers and staging. I just dont know what to do to correct it. I has done it more so now that it is getting cold. The list of mods is: 6.2L LS3 w/ 24x reluctor, Comp Cam 224/230 dur. .581 in. / 591 ex. @ 114 LSA. Factory 90 mm throdle body fly-by-wire. K & N cold air intake. Factory MAF 03 silverado SS. NGK TR-6's . 3200 stall converter. I got my idle low but even with it up at 800 it still does it. Any Ideas?
Attachment 15438

Attachment 15439

I'll give you the same advice too...

http://forum.efilive.com/showthread.php?t=4661

I know it's "the dark side" for some of you folks...but, see if you can find these tables in HPT.



You issue may be timing related too. If your timing is bouncing around during decel and light throttle application, it may be perpetuating the problem.

[Bill@HPTuners]

Originally Posted by SSpdDmon
http://forum.efilive.com/showthread.php?t=4661

I know it's "the dark side" for some of you folks...but, see if you can find these tables in HPT.



You issue may be timing related too. If your timing is bouncing around during decel and light throttle application, it may be perpetuating the problem.

You should make up an HPT version of that thread

All of those tables should be under Engine-idle if im not mistaken

[RPM-silveradoSS]

This may be a stupid question, but what is RAF? I was lucky when i figured out a knock sensor issue. I am VERY new to tuning. I have tried tweeking the timming a little and rasing the idle and it seems to have gotten worse. It idles fine when just sitting their. When u touch the gas and the RPM's come down they dont stop or it will try to save itself and serge then die or stablize.

[Bill@HPTuners]

http://www.hptuners.com/forum/showthread.php?t=9552

[vortec]

you need to command a higher idle and work on base running airflow table
Throttle cracker will cause that problem also.Throttle cracker is way to aggressive