Engine surge

Jim Schultz

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Dec 22, 2019
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San Antonio Tx
I have a 2012 GT 500 with about 80k miles. Very little mods as far as I know. Only exhaust and a mild tune.

The issue I’m having is under moderate acceleration the boost surges. Seems to only happen under about 10PSI boost. Will drop 5 psi then come back. Under full throttle it doesn’t do it but I’m sure its not working correctly

I just want to know which way to start looking. Injectors, vacuum leak or throttle body.

This all started after the dealer cleaned the injectors and has got worse over time. Started minor and now its just annoying.

Any help would be great.
 

moncho

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Seems like your rapidly loosing vacuum and intermittently activating the bypass valve on the blower. Since it started right after the injector work it's conceivable that they don't have an injector/s sealed properly which would likely present a vacuum leak.

If I'm way off I'm sure someone will chime and set it straight.

Cheers,
Ray
 

Catmonkey

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The vacuum lines to the bypass are thin vinyl material and with high mileage can become brittle and break easily. Your dealer might have cracked it in the injector cleaning process. You might want to take a look at that and see if you can find any codes stored in the PCM.
 

Mojo88

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I'm a firm believer in the "Occam's Razor" principle. Occam's razor simply states that of any given set of explanations for an event occurring, the simplest one is most likely the correct one.

If it started immediately after the dealer worked on the car, then it's most likely that the dealer disturbed something IMHO. As others are stating, could be broken/cracked line, or maybe dealer knocked off (or loosened) something unintentionally. Get in there with a good flashlight and look closely at everything. Wiggle things around and see if something's loose. A small crack in a vacuum line might not even be visible unless you wiggle the line. The car is 8 years old with 80k miles, so that means some of the plastic lines/fittings could be a tad brittle.
 

PM-Performance

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I think it would be pretty sad if the lines deteriorated already on a car this age, but agreed that it is likely a vaccum leak.
Check all the vaccum lines yourself. Smoke testers can be had for cheap as well.

#1 reason to start learning to work on cars yourself. Dealers charge lots of money and can still break things/not do things right just as much as you can. Plus side is you know how to diagnose it when things go wrong if you learn to work on the car.
 

Jim Schultz

New Member
Joined
Dec 22, 2019
Messages
3
Location
San Antonio Tx
I have a 2012 GT 500 with about 80k miles. Very little mods as far as I know. Only exhaust and a mild tune.

The issue I’m having is under moderate acceleration the boost surges. Seems to only happen under about 10PSI boost. Will drop 5 psi then come back. Under full throttle it doesn’t do it but I’m sure its not working correctly

I just want to know which way to start looking. Injectors, vacuum leak or throttle body.

This all started after the dealer cleaned the injectors and has got worse over time. Started minor and now its just annoying.

Any help would be great.
 

Jim Schultz

New Member
Joined
Dec 22, 2019
Messages
3
Location
San Antonio Tx
Thank you to everyone who has responded.

I need to clarify how the dealer "cleaned" the injectors. They hooked up some kind of spray can and sprayed that through the engine while it was running. Kind of a BS way to clean them IMO. I did check all of the lines and they are in great shape. No issues that I could find. So that leads me to the boost valve or possibly a code. Can I check the boost valve and if so how?? As for the codes I'll check on that when I get the oil changed as I have that done by the dealer for now. I am using a different dealer too btw because I wasn't real happy watching them clean my injectors.
 

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