Idle surge/trouble 408, decent cam size.

[sslow 4.8]

Hey, been trying a couple things that I know how to do, been having a heck of a time getting it to idle.

It does these things:

*Surges cold start
*Surges warm start (not as bad)
*Will cut off in P/N after a quick rev to 2500 rpms (idle drops low, surges, dies)
*Will cut off immediately when put into gear.
* will idle IF and only if i play w/ the throttle for a while and it will only idle clean after doing this when hot.

Tune is attached.

Specs on car:

408 Iron Block (6.0 bored .30 over)
12:1 Compression
Trick Flow 215 Heads
Cam motion 243/245 650/650 112lsa

fast 90/90 intake
reg. tb... wire driven.
90mm tb
85mm maf
255lph walbro
42# inj.
61 psi fuel pressure
kooks 1 7/8" lt headers to 3"

[sslow 4.8]

ttt... thanks

[Sam88gta1]

There is alot of info on this forum just have to search for it.

You need to search for the Russ K idle config and also read all you can about how to use it correctly. If you have any questions be sure to search first.
You are a few simple changes away from having a near perfect idle.

[sslow 4.8]

Thanks Sam. Thats why i posted... been searching for a while on ls1tech about things and here and have been working on this tune for 3 days. I dont have a whole lot of time to mess with things as I work between 70-80 hours a week, but Ive been around for a while, i understand about searching before i post.

I did the idle config in hptuners. That part is fine from what I understood. Im trying to figure out now what else I could be possibly missing. I was asked earlier yesterday evening if it was ol or cl... and its ol. So that might have something to do with it... never tuned for idle in ol before. But then I was told that it is easier to tune in ol.

There is a guy on performancetrucks.net that posted a very nice and step by step idle tuning for hptuners. Going to follow that and see if it gets me anywhere.

Link to that:
http://performancetrucks.net/forums/...highlight=idle

[sslow 4.8]

heres the thread. they combined them this morning after i asked for it to be stickied :thumb:

http://performancetrucks.net/forums/...ht=idle+tuning

[Sam88gta1]

That is good info but some things were left out and need to be adressed. The main reason most cars will not idle is cause of the amount of fuel that is induced on startup. Fixing that and the underspeed timing table will cure 80% of your problem. If you can't get it straight I'll post a modified tune that will idle like a charm.

[SMOKINV8]

Running Airflow is the main part of your problem, fueling is the other primary part. IME, the underspeed table can help bandaid things, but it isn't usually the root of the problem.

[sslow 4.8]

thanks, yep we got it today. I almost took a video of it and posted it... sounded like pure music.

I took that link i posted and did it step by step, doing the in gear idleing tweaks tomorrow. That is an awesome step by step for hptuners beginners or for those who havent tuned for a cam in a quite sometime like myself, lol.

[sslow 4.8]

That is good info but some things were left out and need to be adressed. The main reason most cars will not idle is cause of the amount of fuel that is induced on startup. Fixing that and the underspeed timing table will cure 80% of your problem. If you can't get it straight I'll post a modified tune that will idle like a charm.

the underspeed and overspeed tables are mentioned as well as forcing it into pe mode and making the 0-1200 inclusive columns to 1.00 just to push it to 14.7 afr at idle. (open looping disable mode during all this of course)

cant wait to try that part out tomorrow.. right now we just got it idling w/o any throttle help whatsoever.. feels good to have it that way after failing miserably the first time, lol.

I'll post the tune when im done w/ the idle tomorrow. thanks again.

need to get that base airflow re configed, that config for base airflow on this forum is a great cfg file to use when logging the idle, very very simple.

[Sam88gta1]

the underspeed and overspeed tables are mentioned as well as forcing it into pe mode and making the 0-1200 inclusive columns to 1.00 just to push it to 14.7 afr at idle. (open looping disable mode during all this of course)

I'll post the tune when im done w/ the idle tomorrow. thanks again.

need to get that base airflow re configed, that config for base airflow on this forum is a great cfg file to use when logging the idle, very very simple.

There is no need to force it into PE at idle to correct the a/f while in OL or CL.

[Sam88gta1]

Running Airflow is the main part of your problem, fueling is the other primary part. IME, the underspeed table can help bandaid things, but it isn't usually the root of the problem.

Filling in the underspeed table with positive values isnt a "bandaid" of any kind. If he removed the extra OL fuel he wouldnt need but 50% of the running airflow he is currently commanding.

[sslow 4.8]

pay no attn to my first attached tune, that was a hack job from his previous tuner... New tune is attached.

and the forcing the pe mode so i know what the afr thing is temporary until he gets his front o2s fixed. Replaced that one and it still wont read, has a short somewhere, thats the reason for the OL and forced pe mode.

[sslow 4.8]

i'll post the new tune later. But i think i got it. Idling like a champ.

Problems that we stumbled on was going into gear it would just cut out. Something interesting there is that he is on the th350 w/ nothing telling the computer that it is in neutral or not. Basically the computer constantly thinks its in gear, but it still starts? Im not sure how that is. But it is reading off of the "in drive" tables while in neutral... after i figured that out it really made way too much sense, lol.

[Sam88gta1]

i'll post the new tune later. But i think i got it. Idling like a champ.

Problems that we stumbled on was going into gear it would just cut out. Something interesting there is that he is on the th350 w/ nothing telling the computer that it is in neutral or not. Basically the computer constantly thinks its in gear, but it still starts? Im not sure how that is. But it is reading off of the "in drive" tables while in neutral... after i figured that out it really made way too much sense, lol.

I modified the last tune you posted but I cant get the file to upload.
You could flash it to a 6 speed tune and copy paste everything over.Thats how I do it when a 4l60 is no longer used.The PCM is always "In gear".

[sslow 4.8]

Oh alrighty... need an email? [email protected]

thanks for that. Which one did you modify the very last one i attached?

Frost had mentioned to me about the short pulse and offset for the injectors. Is there a chart for how to set these up according to fuel pressure and injector size?