Hi, this is Shogen4. Oscillating engine RPM surge at idle.

shogen4

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Hi, this is Shogen4. My 2013 SHO has developed an oscillating engine RPM surge at idle. Fine at any load or speed however the engine sound a bit different under high acceleration. If I'm in gear, the car will surge forward a bit while the breaks are applied. When inside the car, it sounds like the radio is on low with a low base setting. Initially, i thought it was coming from another car.

The engine light has been on and checked. The dealer told me the timing chain id loose which has become a common problem for the SHO-V6 Twin Turbo.

Any thoughts?
 

FiveLeeter918

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Good morning, and welcome to the forum.

How many miles are on the car? Do you know specifically which CEL code you are getting?

The surge sounds like a vacuum leak to me that is causing the engine to hunt for desired rpm and it's allowing the car to continue to try to accelerate despite you braking. When it is surging while braking, if you let of the brakes will it accelerate on its own?

I would start by cleaning the throttle body, both map sensors, and checking the engine bay for any leaks or loose vacuum lines.

If you are getting a P0016 code, you're due for timing chains and the issue you're having may be the cams out of alignment.
 

shogen4

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Good morning, and welcome to the forum.

How many miles are on the car? Do you know specifically which CEL code you are getting?

The surge sounds like a vacuum leak to me that is causing the engine to hunt for desired rpm and it's allowing the car to continue to try to accelerate despite you braking. When it is surging while braking, if you let of the brakes will it accelerate on its own?

I would start by cleaning the throttle body, both map sensors, and checking the engine bay for any leaks or loose vacuum lines.

If you are getting a P0016 code, you're due for timing chains and the issue you're having may be the cams out of alignment.
Hi FiveLeeter918,

89,900 miles. Do not know the code however the dealer told me the car has a timing chain issue. I have not check the codes to see if there is another. It surged just once while I was moving up the driveway last night not touching the gas pedal. Will not accelerate on its own. Seem to be associated with the idle surge. Slight brake pressure keeps that from happening. No problems when I'm driving at speed and sounds fine. However when stopped, the engine feels like it wants to surge forward or like cutting out. Haven tried letting my foot off the brake to see what happens.

Thanks for the impute. I'm worried I may have damaged the engine by not jumping on the timing chain fix.

I picked up a 2015 SHO with only 900 miles. Turns out it was storied in a condition warehouse and somehow forgot about during COVID-19. It was used for after market parts laser mapping. Had it check by two mechanics and a bump shop. All agree it was basically brand new. I was under it with my brother and it certainly looked that way. Inside is untouched. Dated 2015 tires with deep tread and with new tire ink markings still on them.
However it's developed a thumb sound from the front that seems to be coming from the suspension. Not a metal sound however like a ratel; not always the same intensity. Sometimes loud but mostly a soft sound.
 

shogen4

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Hi FiveLeeter918,

89,900 miles. Do not know the code however the dealer told me the car has a timing chain issue. I have not check the codes to see if there is another. It surged just once while I was moving up the driveway last night not touching the gas pedal. Will not accelerate on its own. Seem to be associated with the idle surge. Slight brake pressure keeps that from happening. No problems when I'm driving at speed and sounds fine. However when stopped, the engine feels like it wants to surge forward or like cutting out. Haven tried letting my foot off the brake to see what happens.

Thanks for the impute. I'm worried I may have damaged the engine by not jumping on the timing chain fix.

I picked up a 2015 SHO with only 900 miles. Turns out it was storied in a condition warehouse and somehow forgot about during COVID-19. It was used for after market parts laser mapping. Had it check by two mechanics and a bump shop. All agree it was basically brand new. I was under it with my brother and it certainly looked that way. Inside is untouched. Dated 2015 tires with deep tread and with new tire ink markings still on them.
However it's developed a thumb sound from the front that seems to be coming from the suspension. Not a metal sound however like a ratel; not always the same intensity. Sometimes loud but mostly a soft sound.
 

rubydist

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If the throttle plate is sticky, or the throttle body motor is sticky, you can get this symptom.
 
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