Yes, same problem with my Stage 2 . Spent a lot of time with Tony A on EB tech support reflashing and datalogging with no joy. Replaced the EB throttlebody and the MAF. Still no joy. I put my foot on the pedal when I start it. At least I don't have to pump the pedal like the four-barrel 351 Cleveland on my 70 Torino on every startup... LOL Good luck.
My issue occurs every maybe 15-30 cold starts. Otherwise it’s a weak start that shoots right back up. only occurs with cold starts. From what it seems is this is a bypass valve issue More than a TB issue. But lets see. I am in the process of having the bypass valve replaced. Lastly Edelbrock knows there’s an issue with the TB. Being the size. It’s very hard to tune for. 103mm is wacky. They are making a 108mm from what I’ve heard which should be much easier to tune for andwill probably fix many issues. you have a 17 and it’s a little different. That kit is known to have TB issues. Mine is an 18 and supposedly those issues with the TB are fixed. Who knows.
I don’t use an Edelbrock tune. Their tunes are known to be terrible. Im on a custom tune and have over 50 hours of revisions in it. I also don’t think The issue is tune related imho. It’s more mechanical. The fact that we have similar issues and different tunes proves that part I believe. And if you watch the bypass valve on start up it’s a delayed response. It does not open and close when it should and causes the stall. This issue combined with the awkward TB size I believe is what is creating the issue. It’s absolutely a vacuum issue. My shop installed an air restrictor in the bypass valve to control vacuum better and it did help a little along with freeing up about 2lbs of boost but still needs a little more. If I was to say how “perfect” my tune is it’s probably in the 90% but there’s still that issue here and there that drives me nuts. And my car definitely never stalls when left alone. Make sure the feature to automatically shut the car off after a certain amount of time isn’t on, on the actual mustang. And yes it’s crazy that Edelbrock hasn’t updated something to improve this. They are definitely aware of the issue. My car is going back to dial in the tune a little bit more from my shop. If any place can do it I know they can.
I believe when actually measured ithe inner diameter of the intake tube is closer to 107 or some weird number. It’s not actually 103mm. It’s slightly larger and is awkward in regards to tuning for that particular size.
Tell me more about this restrictor in the bypass valve! How do you mean it freed up 2lbs of boost? You’re making 2 pounds more than before they did this modification?
Wait…so you’ve got a restrictor installed on the bypass valve supply line, to slow the opening/closing of the valve.
When a bypass valve doesn’t open or close when it’s supposed to you can lose boost. If it’s not closing all the way at WOT for example you can lose boost which is common. By controlling the vacuum, it frees up boost that would’ve been there if the bypass valve had been working properly from the beginning. The valve still is opening and closing in a delayed manner on start up but it seems to be functioning better overall now. But this isn’t something I just did. My shop did it and revised the tune based on the airflow change.
honestly I’m not the shop, tech or tuner. I don’t try any of this. They do. I trust them fully with the car. The shop is JDM Engineering and are well known engine builders and tuners. Anything they do in my eyes is the way it needs to be done So if it’s a possibility they have already tested it. From what I gather and understand there’s no air restrictor in the “integrated” Edelbrock bypass valve as is. They modified it to have one So it would function more appropriately.
That would explain why there in a restrictor in the line. Going to the bypass valve. It also explains why it opens and shuts immediately like a light switch without it in the line. This allows you to tame the way it responds with just changing out the restrictor inside the bypass line.
the Bypass valve is opening and closing delayed. It’s functioning better because of an added air restrictor. It did not have this prior to them installing one. I am in the process of getting the bypass valve replaced by edelbrock because it is to be assumed based on the visual and actual evidence that this is the reason this blower has this issue. There’s also the still a chance it TB connected and a slight chance that this is unfortunately as good as it‘s gonna get in regards to their design and my shop is just going to have to keep tinkering away and eventually will perfect it.
Did you leave the restrictor in the bypass line too?