Singular knock on warm start

[dontoya7]

I was wondering if anyone else has had the same issue.

Notes about vehicle:

• Car is brand new with roughly 1200 miles
• I changed the oil at 1000 miles using PUP 5w-30 (some burning but not a concerning amount, oil was also clean)
• Didn't get tick after changing
• RPMs were kept under 4k until 1000 mile oil change
• Does not have active exhaust
• Does not have performance pack
• Vehicle is stock

The knock does not happen on cold start. I have to drive the vehicle up to temps, park/shut off, then start the engine for the knock to occur. It's very audible and shakes the car.

Different ways I've recreated the event after getting the car warm:

• Immediately turning the car on after parking
• Waiting 10 minutes after parking and then turning the car on
• Reversing into park will result in a knock whether the car is immediately started or 10 minutes after parking
• Driving into park will also result in a knock whether the car is immediately started or sits for a little

Sorry if this is some trivial fix that I've overlooked or its a non-issue, it's my first mustang and I don't know alot about cars. I haven't had any other issues aside from the knock, the car drives perfectly fine.

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[Xiaoqian]

Thanks for updating it
Somehow we have to get use to it and follow normal D to P steps to avoid it.

What i do is i got from D To N wait for 1 sec
then N to R hold it for 3 secs and put handbrake and then to P
I dont get this jolt at all on startup!
If i dont follow it i do get a little jolt.

You can try this. Some of us have been having the same issue. And this procedure was offered by one of us. I tried and it seems to work for me. Haven't figured why this happens though. And this is the link that you can find people who have the same issue.

https://www.mustang7g.com/forums/threads/knock-noise-at-startup.161027/

 

[Gregs24]

As I replied in the other thread too.

It may be the exhaust popping. My S550 used to do it on a hot start as does my S650. From inside the car it feels like it is underneath you.

 

[erocker]

Well I've definitely never heard my car belch like that on startup.

 

[Zig]

Almost reminds me of the manual transmission 1st gear thump.

 

[Knacht]

I was wondering if anyone else has had the same issue.

Notes about vehicle:

• Car is brand new with roughly 1200 miles
• I changed the oil at 1000 miles using PUP 5w-30 (some burning but not a concerning amount, oil was also clean)
• Didn't get tick after changing
• RPMs were kept under 4k until 1000 mile oil change
• Does not have active exhaust
• Does not have performance pack
• Vehicle is stock

The knock does not happen on cold start. I have to drive the vehicle up to temps, park/shut off, then start the engine for the knock to occur. It's very audible and shakes the car.

Different ways I've recreated the event after getting the car warm:

• Immediately turning the car on after parking
• Waiting 10 minutes after parking and then turning the car on
• Reversing into park will result in a knock whether the car is immediately started or 10 minutes after parking
• Driving into park will also result in a knock whether the car is immediately started or sits for a little

Sorry if this is some trivial fix that I've overlooked or its a non-issue, it's my first mustang and I don't know alot about cars. I haven't had any other issues aside from the knock, the car drives perfectly fine.

Sounds like something inside the cabin.

 

[dontoya7]

You can try this. Some of us have been having the same issue. And this procedure was offered by one of us. I tried and it seems to work for me. Haven't figured why this happens though. And this is the link that you can find people who have the same issue.

https://www.mustang7g.com/forums/threads/knock-noise-at-startup.161027/

I can confirm I haven't heard the knock on a warm start when following these steps so far. I'm also taking the car to the dealership tomorrow for a diagnostic.

 

[Xiaoqian]

I can confirm I haven't heard the knock on a warm start when following these steps so far. I'm also taking the car to the dealership tomorrow for a diagnostic.

Let me know what your dealer has to say about this issue. Even if the procedure works, I still want to know why this is happening to us.

 

[dontoya7]

Let me know what your dealer has to say about this issue. Even if the procedure works, I still want to know why this is happening to us.

I've been to two different dealerships and even went to the second one twice and nobody has been able to figure it out. Since the car isn't throwing up any codes nobody really knows how to approach the issue without taking the car apart for an extensive and lengthy diagnosis.

 

[Starship Enterprise]

As I replied in the other thread too.

It may be the exhaust popping. My S550 used to do it on a hot start as does my S650. From inside the car it feels like it is underneath you.

An exhaust pop doesn’t make the car try to lurch forward, as in my case.

 

[Gurney]

Hi,
Same issue here. Happens only and everytime I start the car if I stopped the car after having driven it in track mode. Pressure is so large it moves the driveshaft (and sometimes the car).

Brought it back to my Ford dealer. They spent a week discussing with Ford Europe technical center and they agreed this was not normal (but they still don't know the exact problem). Ford agreed to replace the transmission under warranty.

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