Car Studdering / Loss of Low End Power

Hey All, ive recently started to experience an issue and i am at a loss as to what it might be. Back end story, the car is an 05 LGT, stg 2 tuned. Recently just did a brand new 16g and turbo inlet. Replaced the yellow top feed injectors with blue top JDM ones. New Plugs done 400 miles ago, all fluids changed. Had a vacuum leak from manifold to MAP sensor and replaced the hose, did idle relearn and it was fine for 50 miles then the problem returned. Currently has 234,000 miles on it and has run great up until a few weeks ago when this who issue start.

 

Now for the issue, when giving the car gas, i will build boost but car will hardly move. From a dead stop, in sport mode, car will start fine then bog down and build boost at the same time. Ill be at 10psi on boost and only doing 40 mph. This morning, with it being cold here in NY i got out into traffic and the car wouldnt go very fast, literally had my foot to the floor, and had 7psi and was crawling, then the boost hit and the car sped up. I can here the air getting sucked into the intake and all, so i know boost is building. I do have a manual boost controller (yes I know) it works and was recently replaced 6 months ago, car has been running fine with it. Wanted to reach out to the forum and see what else people might have to add. I am swapping the pedal assemblies and seeing if that helps and i am going to clean the throttle body as well. MAF was cleaned as well as the MAP sensor also.

 

Any help or input would be greatly appreciated.

Did you get a protune after the turbo and injector changes?

Yes car has been protuned for 7 years, on the turbo. I did not get the car retuned when i swapped the injectors as they were the same CC from what i was told. car ran great for a few weeks after the injectors. This issue just started around beginning of November.

Do you have any way to log?

 

You are going to need some data to point you in the right direction.

 

Fuel trims, target boost vs actual boost, requested torque, etc.

 

Couldn't hurt to start with a smoke test.

Couple of thoughts.

Which tranny? Any thoughts that the clutch or torque convertor is slipping?

 

I wouldn't be positive that the yellow top and blue top are the same, I'm pretty sure there is some difference between them, but not sure if it would cause what you are describing.

He said sport mod, So 5EAT auto. You need a retune after 7 year man. have a tuner look it over soon.

having a friend hook up romraider this weekend and check everything. I also got a spare pedal from a friend in case its the throttle position sensor on it. Car has been bulletproof since Mike Botti tuned it. The transmission shifts great no issues of slipping. Its the low end build from a dead stop. Shifts fine from first to second and then starts to build boost and then it builds boost but the car doesnt take off like it used to. I also got my friends ap but it is not married to the car, im not sure i can log anything. Also i am getting absolutely no codes what so ever on the scan tool or the AP. A retune was in the future. Smoke test did reveal a leak in the turbo inlet so that is one reason i replaced it.

He said sport mod, So 5EAT auto. You need a retune after 7 year man. have a tuner look it over soon.

 

 

 

Manual has si drive as well.

 

Did you get it retuned for the new turbo? Or did you have a 16g on there before and just replaced it with another?

 

You won't get anything from the ap unless it is unmarried from their vehicle and married to yours is my understanding.

 

 

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Car was previously tuned on the 16g, after 118k on it it blew a seal and i got a brand new exact replacement 16g. I replaced the peddle assembly from a working LGT my friend had with no difference. I am going to replace the entire throttle body tonight. The spare he gave me i clean up and scrubed any crude off it. Also cleaned the pins for the plug. Fingers crossed this is the issue. If not it will be going to a shop to be looked at and then a re-tune. The AP is unmarried that i got from my friend. I have not married it to my car as i didnt want to mess up anything on the ECU with the exisiting E tune on there.

Marrying it shouldn't mess with your existing tune. If you have a non open source tune you wouldn't be able to change anything but I think you should still be able to log, and then you could divorce it. But shop is always an answer too. Mine is about to go into the shop just because I don't feel like dealing with weather.

Issue has been resolved. It was the existing throttle body position sensor. Took the old throttle body off and man it was covered in carbon build up and a film of oil. Swapped it out for a used one that came off a working car my friend had, swapped it over, plugged it in, car idles great, throttle response is back, AFR is stable and gas mileage has returned. Ill be adding throttle maintenance to the records now. Car drives great.