TheGreenDragon
Dopamine-seeking Missile
I've had my 2015 Sonic LT Turbo, 6 speed manual for just under 20,000 miles now. I think it has exactly 19,500 on the odo right now. Car has been in and out of service department for warranty work about 6 times; always for cosmetics and never performance issues. I have never replaced the spark plugs, air filter, and the oil has always been changed at 3,000 miles. Internals are completely stock.
Well, I've begun to notice something odd lately. When I first got the car, the turbo would spool at just above 2,000 rpm. If the A/C was on, the turbo would spool closer to 2,500. I didn't know how to shift at first, so everything was very jerky.
Lately, however, the turbo has become unpredictable. There are some days now where I could swear the turbo doesn't spool until 3,000 rpm. I roll on the gas, shift to second and feather out with gradual throttle, and WHAM. I get a lurch, like the car just doesn't have enough power to make the transition.
Following that, if I mash the gas once the gear change is complete, the car grumbles along like a naturally aspirated engine, when suddenly it hits 3,000 rpm and surges forward. It does this 'surge' twice on really bad days. Once at 3,000 rpm and again at 3,500.
I have no idea what is going on. Intake manifold looks good (and I don't have the equipment to test for boost leaks) and the dealership gave me a car health report last time I brought it in, which said all my filters and plugs were fine.
I thought this was my imagination, until I got a "good day" where the car had consistent boost through the entire rpm range. That night and day difference made me realize that I really do have something wrong; it's just so subtle that I couldn't tell it was there. Now it bugs the crap out of me and makes me want to punch the console when the car refuses to spool.
Any ideas?
P.S. The "good days" generally tend to be pretty warm outside. Not sure why this is the case, but having a really warm day generally solves this strange problem.
Well, I've begun to notice something odd lately. When I first got the car, the turbo would spool at just above 2,000 rpm. If the A/C was on, the turbo would spool closer to 2,500. I didn't know how to shift at first, so everything was very jerky.
Lately, however, the turbo has become unpredictable. There are some days now where I could swear the turbo doesn't spool until 3,000 rpm. I roll on the gas, shift to second and feather out with gradual throttle, and WHAM. I get a lurch, like the car just doesn't have enough power to make the transition.
Following that, if I mash the gas once the gear change is complete, the car grumbles along like a naturally aspirated engine, when suddenly it hits 3,000 rpm and surges forward. It does this 'surge' twice on really bad days. Once at 3,000 rpm and again at 3,500.
I have no idea what is going on. Intake manifold looks good (and I don't have the equipment to test for boost leaks) and the dealership gave me a car health report last time I brought it in, which said all my filters and plugs were fine.
I thought this was my imagination, until I got a "good day" where the car had consistent boost through the entire rpm range. That night and day difference made me realize that I really do have something wrong; it's just so subtle that I couldn't tell it was there. Now it bugs the crap out of me and makes me want to punch the console when the car refuses to spool.
Any ideas?
P.S. The "good days" generally tend to be pretty warm outside. Not sure why this is the case, but having a really warm day generally solves this strange problem.
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