Manifold Swap Diagnosis Help

[Jakewright600]

Hi all, I have a manual 2016 GT and I did a 2018 ported manifold with 47lb injectors. Got it all on and put the tune on and upon start up it seems to be working itself out like usual after a new mod and tune, but then rpm’s started climbing and climbing while in neutral until eventually I shut it off when they seemed to level off around 2500. headers were glowing red

the next day I double checked everything again, re flashed the tune and it was basically doing the same thing, but I took it around my neighborhood to see if it just needed to learn the tune. While driving and in gear it was completely fine, but when you clutch in to shift the rpm’s spike up again to like 1600-2000. Car did throw a p0507 for high idle.

I think I’m running lean based off my headers glowing red the first time, but am at a loss as to what could be causing the rpm spikes and high idle…vac leak? Bad injector? Bad sensors?

brand new here so appreciate any help or input!

thanks!

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[Rusty67]

Sounds like you have a vacuum leak. Try getting a can of brake cleaner and spraying it in different spots around the motor. Don't go nuts and spray all at once. Spray a little bit in a specific spot and wait for the engine to change what it is doing. That can help find the leak. It is possible a gasket isn't sealing or that you have a line that is not all the way on somewhere under the hood.

P.S. don't use carb cleaner, it will damage rubber.

 

[SheepDog]

Vacuum leak. Like Rusty67 said, spray short bursts of brake cleaner around the throttle body, intake piping, intake manifold, basically anything after the MAF sensor. A more precise way to tell if you are spraying in the correct area, is to have your tuning device or OBD2 dongle/app showing Short term fuel trims. If you are in the right spot, you will see the fuel trims change towards negative when the engine sucks in the brake cleaner.

 

[Jakewright600]

Thank you! Will give this a try tonight!

 

[SheepDog]

Thank you! Will give this a try tonight!

If you are seeing the exhaust manifolds glowing red, you have a large leak. Don't drive the car until you can fix it

 

[K4fxd]

Have you done any logs? An idle log will show a vacuum leak. Many things can cause the high idle. The glowing headers can be caused by retarded timing trying to reduce idle.

What tuning device?

 

[Jakewright600]

Have you done any logs? An idle log will show a vacuum leak. Many things can cause the high idle. The glowing headers can be caused by retarded timing trying to reduce idle.

What tuning device?

PBD tune with x4…I sent in idle logs and asked if they can tell anything from it, but haven’t heard back yet.

 

[K4fxd]

Do you remember what the short term fuel trims are? "STFT"

 

[Jakewright600]

Do you remember what the short term fuel trims are? "STFT"


Here is the initial idle log. Has 2 Short term fuel trim columns.

figured this was easier than trying to explain it

 

[K4fxd]

It sure looks like it is getting unmetered air.

 

[Rusty67]

Quick tip for when you are spraying to try and find the leak. You should use the straw the can comes with to keep the spray pattern nice and tight so you can be more precise as well as get it directly into the nooks and crannies under the hood without over spraying everywhere else. Helps to keep the guess work down.

 

[Jakewright600]

Found a big ass vacuum leak in a hose. Thank you all!!

 

[NGOT8R]

Found a big ass vacuum leak in a hose. Thank you all!!

Can you please post a pic of the hose that was the culprit?

 

[Jakewright600]

Already replaced and tossed it, but It was one of the ones that we repurposed from the brake booster etc. line. Im assuming we knicked or hit somewhere and missed it first time around. Also we reused the gasket from the original manifold on the throttle body, switch to the new one this time, could have also played a part.

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