Intermittent stumble at startup

[mikel]

Yes, based on the last tune written you posted.

[wcking]

Installed the custom tune last night. No issues yet. I'll keep you posted. Thanks for your help.

[tvalliere220]

my 2013 silverado 1500 with a 5.3 is doing the same exact thing on cold start up with 87 octane tune has cold air intake along with custom exhaust as well.

[wcking]

Unfotunatly the stumble ocured this morning with the custom tune installed.

[xcr-700]

Not sure if we are experiencing the same thing, but my 2006 Avalanche 5.3 sometimes has what I describe as a kickback when starting.

In the old days you might get something like what I am experiencing when starting if the timing was set too high.

It doesnt backfire through the intake, but I have wondered if it was going to, or possibly break the starter.

Its a very strange and hard to describe situation, and it doesnt happen very often but when it does its a bit unnerving.

It only started for me after adding the Diablo tune from my Predator Tuner.

Again it doesn't happen enough to even remember to look into it, so I havent even looked into it.

Not sure if this is what you are experiencing, kickback or "almost" backfire during starting, but thats the best way I can describe it.

GH

[Zach]

Ok, that gave me some good data. The tune I had you load labeled, _test was all stock parameters. This proves that it's something with the truck. When you flash the tune in, whether it be a stock tune, or one of our canned tunes, you're resetting any learned value in the PCM. That could be why the first few times you start it after changing tunes, everything seems better, but gradually gets worse and develops a stumble on start up.

[xcr-700]

Hi Zack,

wondering if its possible to use a Diablosport tool to monitor ignition timing during startup?

When it happens to my truck, it really feels to me like the initial timing is either very high or it jumps to a higher number just as the motor starts.

Would that be captured while logging???

Either way, your idea that its something the truck is doing vs the specific tune makes sense, but in my case its not a regular event, very unpredictable when it will happen.

Thanks

George

[Zach]

You can certainly try to log the startup and I will look at the log.

Just get everything set up and logging with the Key on Engine off, then start it up and let it run for maybe 30 seconds, then stop the log and save.

[xcr-700]

It could take many attempts to get this logged, as in my case it does not happen often. Maybe once every 2 months,,,

If its happening for someone else on a more regular/predictable basis, this might be an option.

GH

[Ill_Born_SS]

Did you ever remove and clean the throttle body?

[wcking]

It sounds like the same issue I have. What your describing is what I experience. in my original post I mentioned "it sounds like a timing issue". I've returned to stock tune and will leave it there for a while in an attempt to recreate the stumble without the tune in it.

[wcking]

Well, yesterday the stumble occured with stock tune restored. I had the dealer reflash the ECM with new updates. They seemed to think it could have somthing to do with the issue. I'll run it in stock configuration for a while and see if the problem shows up.

I want to thank the great support from Zach and others at Diablosport.

[Shadow1120]

Mine did the same stumble the very first time I started it with the 87 tune installed, but has never done it since,been about 2 months now.I've got a 09 sport 5.3.