LNF Idle Surge

[JBravoXC3]

Cold starts are awful. Or when it's a damp morning. It starts fine but then the RPM's jump all over the place and the car barely runs. After 30-45 seconds it calms down and idles ok, but at warm idle still does not seem right. The SES light is on. We haven't touched the timing at all (except trying to adjust it to fix the idle, that we read on another threat here) or fuel so I'm not sure why this is happening??? It's even worse with the AC on.

I'm a tuning n00b, my cousin has been teaching me and doing the tune. This is his first LNF though and it's much more complicated than his Buick GSX, so we really don't have anyone to turn to for help. So then I registered here!


I have a copy of our tune, see attached.

Also we have disabled the post cat O2 sensor. Is that the same as disabling the catalyst warm up? (I had a ZZP downpipe)

Anything will help, feel like 2 blind guys trying to find our way out of a maze

[JBravoXC3]

Oops didn't attach the tune. You'll see it's not much different from the GMS1

[HNRClothing]

http://www.hptuners.com/forum/showthread.php?t=36029

[JBravoXC3]

tried that weeks ago didn't seem to work

[silverbullet08]

holly cow that was a old thread lol. I really dont remember posting it.
Try posting up a log of cold start and letting it warm up all the way through a couple minutes past when your STFTs start reacting. A copy of the file your working with will help also. The thread posted above was mainly aimed toward the people who forget to tune for the higher load that AC creates on this motor. Do you have the cat warm up disabled? if not your going to be using a higher rpm cell than your normal idle cell. That will caue it to run funky till idle settles.

Sorry just noticed you posted the file.

[silverbullet08]

Test this out, this is like a spoon fed file for you. This file has a few changes to help with idle, some changes I do on all lnfs and some of the other stuff is to help smooth things out. The cam tables in there are just for the cat warm up delete and a little better milage out of cruize. You may be able to gain more milage and or power out of them but you need to do some reading to get into that area of tuning. If this doesnt help then you probably have another issue somewhere that needs to be looked at. Like I said this is just a base file for you to start with and get you going. There is a lot in this file that could be changed but I left it the way you had it due to not knowing what mods you have ... and so on. let us know how it works and post a log!!!

And your codes you turn off for a catless downpipe are still in effect, probably why you have a check engine light

[projectlnf]

for some reason when i turn off cat heating on a cold morning it will not idle at all i have to give it some throttle and it picks up and i have to hold it at 2000 to get it to about 120 ect and then it will idle

[cobaltssoverbooster]

Mine doesn't idle at all with cat warmup off

[gmtech16450yz]

Ok guys, hang in there. I'll post up the fix for all of these idle and ign timing problems as soon as I get back from my trip.

[stromboli86]

Mine used to do the same stuff after i turned the cat warmup off, then it got better after i started messing with the camshaft cold tables and raised the cold desired idle speeds. If it was actually still cold out i could mess with it more but thats not the case lol. If i remember correctly the car liked the intake cam value around 0* to 3* rather than 10* like warm idle, dont remember where the exhaust cam was tho... think it was also near 0*

I also noticed once turning off cat warmup, it does not disable the catalyst heating idle tables. It uses catalyst heating until 104*F, it will switch between the idle cold and warm tables according to the Cat heating Factor table. Then it moves to the Base Angle idle cold and warm tables and follows the Idle Factor table for those. Basically i used all 4 idle tables to ramp from around 0* to 10* once warm for the intake.

This is what i noticed in the short time i messed with it so it might help

Edit: or just wait til GMTech post the fix!

[gmtech16450yz]

http://www.hptuners.com/forum/showth...637#post297637