TL;DR: 05LGT 165k - running poorly, lack of power but reading full boost. Shop replaced O2 sensor, injectors, now doesn't reach full boost, new scary rattling noise.
OK. Sorry for the potentially lengthy post but I'm at a loss for what to do about this.
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Let me start by saying this shop has done all of my work on the car for the past 6 years and for the last 5 have been awesome and friendly.
Began a few months ago, car would stutter and hesitate under acceleration, and really feel underpowered when it smoothed out. I have the Torque Pro app so I can monitor some things including boost (17.5psi, which is correct for the max boost per my stage 2 tune at this shop), and I was reaching that number even though it didn't feel right. So I bring the car to the shop and describe the problem.
Shop tests it and says I'm running lean, blames O2 sensor. I OK the work and it is replaced. I pick the car up, and it is great again, everything is reaching the correct numbers, the car feels responsive and pulls hard just like it used to. I'm happy. UNTIL that same day, it begins hesitating again and again feels underpowered. I check the boost numbers, it is still hitting the target of 17.5psi, but stuttering and feeling slow again. I call shop back and say hey, that problem came back.
Shop says O2 sensor could have been masking another problem, explains that injectors would be the next thing to replace to fix this issue (to their credit they mentioned injectors when I picked the car up from the O2 sensor replacement). I'm hesitant to do it since I'm trying to sell the car and don't want to put more money into it than I could sell it for, but I OK the work again after getting reassured that this is the most likely cause of the problem and the shop owner would try this if it were his own car.
Work is done, I pick it up and drive it home. No longer stuttering, but still feels not quite right. I load up Torque and see that I'm now only hitting 13psi instead of the 17.5psi, and there is a light metallic rattling noise when boost starts to build. I am not happy. I call the shop and explain that there is a new problem, ask about what they had to do to the car.
Shop says they replaced the injectors. I asked if they had to change anything with the tune. Shop says no. I tell them I'm reading 4psi low and there's a new mechanical noise under acceleration, maybe something went wrong with installation? Shop gets immediately defensive, tells me my car is trying to fall apart at every corner. I ask why nobody told me there was a new noise and the car wasn't hitting full boost. Shop says they do a pressure test but don't take the cars out for a drive after service and floor it, and running lean could cause the turbo to reach higher boost pressures since it is running hotter, so new injectors running correctly makes less boost. (You don't need to floor it to get the noise to happen. You can't drive without the noise happening). Shop offers to inspect the car for free (after much questioning on my end) but says it sounds like my turbo is dying and I am going to end up putting a lot of money into a dying car.
A couple of things bother me about this. One is that they didn't test the car before calling me and telling me it is done. Another is that on both occasions the owner called me and asked for payment over the phone while telling me the work was complete. (what business makes you pay for something before you pick it up?) A third is that this latest issue seems very different than what I brought it in for and just HAPPENED to pop up after bringing it back from getting work done.
Could somebody help me sift through all of this information? I don't know enough about these cars to make sense of any of it. Will a lean running turbo make higher boost? Wouldn't a dying turbo not hold that boost even if it was running lean? What could have gone wrong with an injector install? I get the feeling that this job was rushed but have nothing to back that up with.
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