'07 Mustang GT surging on startup

[Scooter70]

I know that we have some Ford tuners who use other products here so I figured that I'd ask the question and see if anyone has encountered this and has a fix. My father has a 2007 Mustang GT and has an SCT handheld with a custom tune on it. The car is 100% stock down to the air filter. When he starts the car cold, the idle will hang at about 3k for a few seconds before settling down. I talked to the tuner (and have seen it myself in 100% stock 4.6L 3V vehicles) but he's not sure what's causing it. My wife's '06 Mountaineer hangs at about 2k rpm on startup so it seems to me that something in the tune is exacerbating the situation.

Has anyone seen this? Do you have a fix so I can talk to the tuner and have him modify the tune? What parameters should I log to try to diagnose it?

Thanks,
Matt

[jah81592]

You can get your tuner to look in the idle section under startup. There is a idle "adder" which does exactly that for a certain amount of time. Get him to reduce these values.

[Scooter70]

We checked "Idle Speed RPM adder for ECT" but that is only adding 300rpm at 70*F and below. It doesn't explain 3500rpm. I'll have to have him check under Startup.

Thanks.

[Screamn03]

I would start here first:

Check the maximum_allowed_spark_table_cold. If it's been changed put it back to the stock values.

Upon cold start alot of timing is pulled for up to the first 60 seconds of operation to make the cats light off quicker. When you retard timing the motor will require more air to run at the same RPM. If you change the maximum_allowed_spark_table_cold to have the timing not get retarded then you will have to redo certain air tables as well, if you don't you will get the condition you describe of excessive flare up.

Hope that helps you out,

[rob82]

It will be within the Startup ETC position vs ECT for crank. The older mustang's do it to. It was in a very similar table within crank fuel I think.

[Justin@VMP]

There are several reasons why it may happen, and there several ways to reduce it.