5.3L swap idle issue Advice needed!!

[53Chevy]

Needing some advice on an issue I'm having. It's a 2000 5.3L with 4L60E in a 53 Chevy truck with a stand alone PSI harness. The engine has a tsp 224 cam 581" 581" 114lsa, pac springs, ls2 timing chain, ls6 oil pump and new maf, iac and map sensors. I can't find any vacuum leaks and the engine has all new gaskets. The problem I am having is that the engine will start and then die right away. The next time I start it it will run and idle good and sound fine. When it doesn't want to run, if you open the throttle just a little again it runs fine. So it's basically a hit and miss stall/no start. At first I thought it must be because of the cam and the pcm not being tuned for it. So most of this tune is copied and pasted from another tune. I am unable to drive it yet because I'm having a drive shaft made so I don't know if there are other issues. Could you guys look at this and give your thoughts please? I am new to tuning so any and all advice is appreciated.

[GHuggins]

Take 10 out of your idle spark advances in your 400, 800 and 1200 columns for drive and neutral and see if that has any effect. Then I would also highly recommend going to the tune repository and copying all of your idle and airflow tables out of a stock 2000 or newer 5.3l with automatic trans setup.

Will also tremendously help if you post a datalog from startup with the problem present.

[53Chevy]

Ok I will try that with the spark advances and I will change the idle and airflow tables back to what it had stock. I have the original stock tune for it. I will try to log a file tomorrow. Or should I just go back to the stock tune and start over? It didn't want idle with the stock tune as well. Thanks

[53Chevy]

So I have tried those suggestions and wrote it in. Still won't start on it's own without a little throttle. Attached are a log of it and the newest tune. What am I doing wrong guys?

[GHuggins]

You said you put a new MAF in... Is it one originally setup for whatever year model you got the operating system out of? Has any tuning at all been done on this? I don't have a way of comparing your tunes right now to check. What happens when you unplug the MAF and try to start it in SD mode? Still start and die? What kind of intake and TB is on this thing? I just had one doing the exact same that wound up being a fast TB issue where air wasn't flowing through the IAC passage efficiently enough. All I had to do to get it going was open the throttle plate up .02volts more on the tps. No matter what I changed in the tune to try and fix it that typically fixes this kind of problem it had absolutely no effect. So was just wondering...

[53Chevy]

The maf is new as the engine didn't come with one. It is for this make and model. Nothing changes when maf is unplugged. When the iac is unplugged it starts and runs at about 1500 rpm smoothly. It has the stock truck tb, intake manifold, heads and coils. So it is basically a stock 2000 5.3l truck engine with a cam, headers air raid cai, new maf, map, plugs, wires and iac. I replaced the iac because of this. It sure sounds the same as what you described. It seems like it is starving for air at startup. So far anything that I have changed also seems to have no effect. I think I am looking in the right area (iac and tps) but not sure how to correct it.

[GHuggins]

Something to try. Not making any guarantee that it helps you, but it shouldn't hurt. Go to your ve table and add 5 percent to your 400, 800 and 1200 rows. Then under idle airflow initial, increase it .5. I think that's the right name? Then see if it helps any at all. Mowton can hopefully chime in as he's better on the Gen 3's. If no effect, see if the throttle plate is adjustable. Hopefully you won't have to do the drill plate trick to fix this.

[mowton]

OK, here goes...Cam isnt too bad (-4 degrees overlap) so lets set idle rpm to 800 (550-590 is too low), Add 1 g/sec to the Base Running AF table and 2 degrees to the stock idle timing.

Put Friction Airflow decay back to stock, (decay has been increased so it has less time to help) and set Friction Airflow Delay to like 25 cam rev's...more time to help before it gets decayed.

Put all the Adaptive Idle Airflow tables back to stock. When we get the idle desired air correct, you won't need that much padding...

Along the stock lines, put the Throttle Cracker enable/disable sspeed and airflow back to stock as well. Do the same for the Cracker.

I am assuming you have installed a stock TB/IAC assembly so put the IAC Steps table back to stock. The steps start at 12 mm2 which is what the throttle opening cresent s/b yield at closed throttle, then the iac steps impart their additional air. While not related, but just to keep everything inline, put the ETC scalar back to .0255 as well.

Now we are going to set up the scanner. Develop a .cfg that utilizes the following PIDS: IAC desired, IAC pos, LTIT PN/AcOff, LTIT Gear/AcOff, Idle Adapt (STIT), Idle Desired Airflow, Idle startup, Commanded AFR, RPM, ECT, MAP, Advance, Throttle Position %, Throttle position (V) and Dynamic Air.

First order of business is to get her started and dial in the IAC. If you haven't already, remove the setscrew from the bottom of the TB and re-install from the top...this will allow easy access for later adjustments. With the .cfg above, and at operating temp, adjust the setscrew so the IAC desired is between 50 and 80 steps and TPS volys is <.8v. Whne complete, turn engine off, unplug TPS and IAC. turn key on (don't start) for 20 seconds, shut off and reconnect connectors. This will complete the relearn process for the pcm and set 0% TPS as closed throttle. Let engine cool down and repeat if needed.

The last step is to log the LT and STIT from a cold start to high temp and update the BRAF based on these results. It is better known as the RussK cfg...

You do want to make sure that before you start tuning the idle/startup, that the VE and MAF are dialed in pretty good. with no drive shaft, suggest you duial them in down from 1200 rpm to say 800 by using the VCM Controls.

I know this is alot, but the Gen III's take a bit more effort then their offspring (E38/E67) :-)

Ed M

[GHuggins]

OK, here goes...Cam isnt too bad (-4 degrees overlap) so lets set idle rpm to 800 (550-590 is too low), Add 1 g/sec to the Base Running AF table and 2 degrees to the stock idle timing.

Put Friction Airflow decay back to stock, (decay has been increased so it has less time to help) and set Friction Airflow Delay to like 25 cam rev's...more time to help before it gets decayed.

Put all the Adaptive Idle Airflow tables back to stock. When we get the idle desired air correct, you won't need that much padding...

Along the stock lines, put the Throttle Cracker enable/disable sspeed and airflow back to stock as well. Do the same for the Cracker.

I am assuming you have installed a stock TB/IAC assembly so put the IAC Steps table back to stock. The steps start at 12 mm2 which is what the throttle opening cresent s/b yield at closed throttle, then the iac steps impart their additional air. While not related, but just to keep everything inline, put the ETC scalar back to .0255 as well.

Now we are going to set up the scanner. Develop a .cfg that utilizes the following PIDS: IAC desired, IAC pos, LTIT PN/AcOff, LTIT Gear/AcOff, Idle Adapt (STIT), Idle Desired Airflow, Idle startup, Commanded AFR, RPM, ECT, MAP, Advance, Throttle Position %, Throttle position (V) and Dynamic Air.

First order of business is to get her started and dial in the IAC. If you haven't already, remove the setscrew from the bottom of the TB and re-install from the top...this will allow easy access for later adjustments. With the .cfg above, and at operating temp, adjust the setscrew so the IAC desired is between 50 and 80 steps and TPS volys is <.8v. Whne complete, turn engine off, unplug TPS and IAC. turn key on (don't start) for 20 seconds, shut off and reconnect connectors. This will complete the relearn process for the pcm and set 0% TPS as closed throttle. Let engine cool down and repeat if needed.

The last step is to log the LT and STIT from a cold start to high temp and update the BRAF based on these results. It is better known as the RussK cfg...

You do want to make sure that before you start tuning the idle/startup, that the VE and MAF are dialed in pretty good. with no drive shaft, suggest you duial them in down from 1200 rpm to say 800 by using the VCM Controls.

I know this is alot, but the Gen III's take a bit more effort then their offspring (E38/E67) :-)

Ed M

See what I meant There's what, dozens of airflow and fueling tables just for startup on the gen 3's?

With the fast 102 junk equiped TB truck I'm in the process of tuning right now, I couldn't do any of the above to get it to keep running cold. Tried changing every IAC and fuel table there was that "should" have fixed it. Only way to get it to run was to set tps to .35v from .33v and IAC counts to 20's when hot down from 50's where it was with hot idle. With it up in the 50's is where I actually caused my problem and it was only present durring colder starts (less than 155ish ect). BUT I also believe the very serious lack of airflow through the IAC passage was my whole issue when it was combined with the airflow demands of the engine and intake. Should have just removed it and bored it out like most advise, but the TP "tweeking" fixed everything for me...

[mowton]

See what I meant There's what, dozens of airflow and fueling tables just for startup on the gen 3's?

With the fast 102 junk equiped TB truck I'm in the process of tuning right now, I couldn't do any of the above to get it to keep running cold. Tried changing every IAC and fuel table there was that "should" have fixed it. Only way to get it to run was to set tps to .35v down from .33v and IAC counts to 20's when hot down from 50's where it was with hot idle. With it up in the 50's is where I actually caused my problem and it was only present durring colder starts (less than 155ish ect). BUT I also believe the very serious lack of airflow through the IAC passage was my whole issue when it was combined with the airflow demands of the engine and intake. Should have just removed it and bored it out like most advise, but the TP "tweeking" fixed everything for me...

Shooting from the hip, that sounds like there may have been a "sneak path" of air not being accountted for...like the hole in the blade was too big?

Ed M

[GHuggins]

Shooting from the hip, that sounds like there may have been a "sneak path" of air not being accountted for...like the hole in the blade was too big?

Ed M

Edit - Sorry mowton, went and reread my post. Meant to say I had to open the throttle plate up to .35v from the previous setting of .33v... It's fixed now.

What I mean by that is that there was no hole in the plate at all... I know I need more air and the iac passage just won't flow it, so I should have either bored out the restricted IAC passage like most do or put a hole in the plate - also like most will do. BUT I found a happy median by just increasing the throttle opening ever so slightly and causing the IAC to close off more when hot. Still has room to close more if need be so not too worried about that. Plus unless the owner is really happy with it, he might be turning around and ditching the LQ4 all together or if nothing else going a different route with it. I've already gotten another 120hp out of it in areas compared to where the last tuner left it (92hp increase peak to peak numbers), so who knows. AND I've still got to finish fine tuning in my fuel and timing tables. She was spitting and sputtering bad when it showed up, laboring bad on the dyno in 3rd gear. Wouldn't even break the tires loose if you tried to powerbrake it - customers main complaint when he was showing everything wrong with the truck?

Anyway 53chevy, more to think about If you do go the hole route, don't forget to add some fuel in those forementioned columns just to get it going and to start tuning.