Cold Start issue - won't run without pedaling the throttle

[travisty75]

My searching has left me with more questions than answers. I've posted this question on a Facebook group (Goat Rope) and received some helpful guiding from a couple of guys, but I'm just taking wild swings with the knowledge they've shared and I can't make any good progress.

e67, 4.8, 218/227 112+2 cam, otherwise stock. Paid for a tune from a reputable Mail Order place, and the customer service and the tune itself was enough to make me start learning this myself. VVE/MAF are really close in the closed loop areas, but the truck won't cold start worth a damn. It will crank over and light off quick enough, but the transition to Open Loop after that is rough, and the truck dies very quickly. I can restart it, but it doesn't stay running without throttle input until there's a little heat in the motor (I'm guessing?).

smokeshow suggested I look at the Open Loop IVT table, and I increased it by about 10% in the lower rows and that helped it hit targeted fuel numbers, but it still doesn't stay running at all. Other threads have indicated drastically increasing these values (increasing the values by 60% total) are what's needed, so I tried that and it wouldn't even start. I dropped back to the increased IVT values, and can at least pedal it to keep it going.


The truck runs and drives well enough, and to be honest I'm sure I could eventually stumble upon the correct combination of values to get it going... But I'm hoping someone can fast-track me by pointing out my failings with my current calibration.

[Gustavo]

48 97x_SD_MAF Cal_22.hpt

[travisty75]

Thanks for the help Gustavo!


Looks like you decreased the FA multiplier by about 45%, turned Proportional Air back on and increased the proportional airflow by 10% (or is that stock? I know I softened mine in hopes it wouldn't overshoot so far), added a gram of air to the base running table up to 800rpm, stepped up the idle in the colder temperatures by 100, idle startup airflow decreased by 5 points-ish... anything I missed?

Would you suggest I just up the base running airflow by another gram and then blend out/interpolate the following cells?


This took a significant amount more time cranking before lighting off, and it also never flared up like the calibrations I've had in the past. It did seem much less lazy after the initial crank/fire though, but I'm attributing some of that to the fact that the engine is still warm.

[hjtrbo]

Add 4g/s to the startup air. See what that does

[07GTS]

set the effective area max fail ecm2175 from 60 to 200 will help it start, also set the dynamic high rpm enable disable higher like 8000, 8100

[travisty75]

Add 4g/s to the startup air. See what that does

set the effective area max fail ecm2175 from 60 to 200 will help it start, also set the dynamic high rpm enable disable higher like 8000, 8100

Cheers, boys. Those suggestions helped a ton. It still has a little dip at the start, but I'll keep tweaking the associated parameters to bring that in line.


GTS, is the idea behind the higher dynamic switching to keep the MAF/VE blended through the rev range?

[07GTS]

looked like u were trying to be SD only just that wasn't set but if u have maf then u have to set few things back, just from your tune i havnt looked at ur logs

[travisty75]

looked like u were trying to be SD only just that wasn't set but if u have maf then u have to set few things back, just from your tune i havnt looked at ur logs

No sir, it's still a MAF vehicle and I didn't have any intentions to make it full SD.

This cal is based off the one I received from the tuner a couple months ago and I've just been adjusting the MAF/VVE to get it inline (he didn't do any VVE tuning). I'm reading a bit more into what you're saying, but it may have been better to start with an unmodified tune. Would you suggest I start with my factory cal and transfer all of the fuel/air tuning stuff over?

[07GTS]

got into the engine diag and set the maf stuff back to stock then leave ur high low as it was, my change before from 60 to 200 shouldn't affect it if it's using the maf

[hjtrbo]

Still wants more air. Add another 2g/s

[07GTS]

may even have to set the maf DTC's back to stock as well, its been SD tuned with failed maf at some stage and not set back correctly for maf usage

[travisty75]

Still wants more air. Add another 2g/s

may even have to set the maf DTC's back to stock as well, its been SD tuned with failed maf at some stage and not set back correctly for maf usage

I added another 2 grams to the Startup Airflow, and after observing a small wobble in the idle during the warmup process, I pulled a gram out of the base running air flow. Throttle input was zero, throttle blade was steady, fueling was constant, but the timing was dropping to 11* when it was overshooting, and would spike to 24 to bring it back up. That appeared that it was getting excessive air and the spark was trying to contain the idle.

It still does it slightly in this log, but it's much more calm.

07GTS - Everything is back to stock as far as I can tell. I used the File Compare tool and found anything out of line and corrected it.

Thank you both for your help with this! It's extremely satisfying to be able to turn the key and not have to do anything to keep the truck running.

[07GTS]

try this few more changes u missed, maf s/s startup i just put figures in there u should see what it needs based on ect and put values in if it needs it, log looks like its running VE as its set to fail still so using this will change it, the maf will show values even when failed and not used, u can see dynamic is following VE not the maf so this tune changes may throw things out but its the way it should be with maf

[travisty75]

try this few more changes u missed, maf s/s startup i just put figures in there u should see what it needs based on ect and put values in if it needs it, log looks like its running VE as its set to fail still so using this will change it, the maf will show values even when failed and not used, u can see dynamic is following VE not the maf so this tune changes may throw things out but its the way it should be with maf

Cheers. I was going off my factory calibration which had the MAF S/S zeroed out. It is attached, in case you were curious.

I also see the other tab I completely missed. Thank you for helping me with that! The log attached is with your changes. It is the smoothest it has been since we've had these cold temperatures. I can't tell you how grateful I am for your help here.


Regarding the MAF S/S table, should I be looking for that to reflect how much air the MAF sees at the desired RPM range for a given temperature? There's not a whole lot of information I can find regarding this table.

[07GTS]

the maf s/s is the values for just at startup when the maf isnt flow steady yet so its a value it can look up as a estimate for where it should be running, once u heat up thru the temps just put the dynamic airflow value in each one and maby add couple g/s more to help with startup should be fine its only used for short time, that log looks better u can see its using the MAF now where before it wasnt and fueling is closer, now u just have to get the vve sorted once the maf is good to tie it all together