1

I have a 2013 Chevy Cruze 1.4l Turbo LT with 100k miles on it. I am the original owner.

Overall this car has been very reliable, but a few months ago it started having intermittent decrease in engine power when accelerating (about 1-2 changes in power output per second).

This can happen when starting from rest but at other random times as well, at lower or higher speeds, usually when trying to accelerate. This happens usually for a certain time (usually not very long - seconds to a couple of minutes), after which the engine runs fine for a while - minutes up to days or even a week or more.

One notable experience is: while on a long freeway drive at 70-80 mph, everything was fine for about 150 mi, after which I felt a sudden decrease in engine power (also intermittently) and was unable to reach speeds higher than 65 mph or so. After about 5 minutes I stopped the car but did not see anything obviously wrong with the engine (idle was fine). After I started again, the symptoms disappeared, and was able to drive for the next 7-800 miles without any problems (over several days). At some point the problem started again, and after a while I saw the engine light come on too. The engine code I got for this indicated a faulty knock sensor. I replaced it with a new genuine GM one, but that didn't fix the problem.

One other symptom that also happens randomly (when starting from rest or during a drive) is a slight but noticeable pinging noise, with the same frequency as the RPMs. This noise is usually on for several minutes after which it stops and it seems to happen more at the beginning of a drive. The power loss and pinging noise don't seem to be correlated.

Here's what I have done so far to try to fix this, either myself or at the shop

  • changed engine oil
  • changed transmission fluid
  • replaced spark plugs
  • replaced the coil box
  • inspected the air filter, which seems fine
  • cleaned throttle body
  • replaced purge valve and cover
  • replaced intake manifold
  • replaced knock sensor

and yet these symptoms keep happening.

Because of their unpredictable and hard to reproduce nature, is very difficult to demonstrate these symptoms to a mechanic, so they don't really know what to do.

Any suggestions?

ADDITIONAL INFO: it seems that the pinging/ticking noise happens mostly after starting a drive. As far as I could tell, the noise doesn't start immediately, but after a few minutes, lasts for a few more minutes and then it dies down and doesn't reappear until the next drive. I'm not sure if this indicates a correlation with engine temperature - in some cases it happened during a new drive but not long after the previous drive, so the engine wasn't cold.

Improve this question
2
  • I would suspect this vehicle needs premium gas since it's a turbo? Have you been using lower grade fuel?
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Jun 21 at 0:12
  • From the manual: "Recommended Fuel Use regular unleaded gasoline with a posted octane rating of 87 or higher". That's what I've been using.
    – Ady
    Jun 22 at 1:58

1 Answer 1

Reset to default
1

Your turbo includes a wastegate and a wastegate actuator. The wastegate is supposed to open and "waste" some of the air pressure that the turbo produces if the turbo pressure exceeds a certain threshhold.

If the wastegate or its actuator are sticking or malfunctioning, all sorts of mayhem can ensue. A wastegate can operate normally and then get stuck open or closed for a time and then return to normal operation for a time.

If the wastegate becomes stuck open, the turbo won't produce sufficient pressure and airflow that the engine needs to accelerate, to climb hills and to maintain highway speeds because the lack of sufficient airflow past the MAF sensor will cause the ECU to reduce the amount of fuel being injected to each cylinder. You will lack horsepower.

If the wastegate becomes stuck closed and the engine is operated at high RPM, you'll get excessive turbo boost and therefore excessive compression, which will cause pinging or engine knock. The knock sensor detecting the knock will cause the ECU to retard the timing and/or reduce the amount of fuel being injected, again limiting power at higher road speeds or higher RPM.

Any decent scan tool connected to your OBD2 port will display manifold absolute pressure. Pressure can be monitored on the scan tool by a passenger as you drive, and soon enough, you'll learn what a normal manifold pressure is under various operating conditions. Then, when the car decides to malfunction, check the manifold pressure. If it's much higher or lower than expected for those operating conditions, that confirms that your turbo's wastegate or wastegate actuator (or the wiring to it or the software that controls it) is malfunctioning.

On the turbo-equipped car that I drive most, the maximum manifold air pressure is supposed to be 2.0 atmospheres (about 29 psi or 60 mm mercury). It's below 1.0 atm at idle, and when driving sedately it's just a little over 1.0 atm. But if I downshift and accelerate with the pedal to the floor, the manifold pressure will shoot up to 2.2 or 2.3 atmospheres momentarily, when I feel the power drop off a little and the pressure immediately drops to 2.0 atm. The ECU has adjusted boost to limit the manifold pressure. It will then stay there at 2.0 atm all the way up to redline.

I'm not suggesting that you should replace anything yet -- I'm giving you a way to diagnose the problem to either confirm or reject the wastegate malfunction theory.

Improve this answer
10
  • This is something they checked and demonstrated to me at the auto shop, that this "wastegate" was apparently functioning normally. While one person was pressing the throttle to higher RPM, then depressing it, the mechanic showed me how the "stick" coming out of that device was moving in or out properly to release turbo pressure. One other detail (that I mentioned in my post) is that the pinging is not correlated with the loss of power, which seems to be inconsistent with how you described the case where the wastegate becomes stuck closed.
    – Ady
    Jun 21 at 3:35
  • @Ady Good, we're halfway there: we know that the wastegate is not sticking while the car is parked and a mechanic is watching. Now all that's left is to confirm that it's not sticking while you're out driving with no mechanic in sight and the engine is misbehaving. The same wastegate can function and malfunction at random and it can stick open, closed or mid-way. Your case is vexing because whatever is wrong only happens when no mechanic is around, so you must become part of the diagnostic team and be prepared to take measurements in the field when the car malfunctions.
    – MTA
    Jun 21 at 11:54
  • Yes, you are right. I'll see if that component can be cleaned or replaced.
    – Ady
    Jun 22 at 2:00
  • @Ady Sigh . . . if you want to replace a part without proving that it's the root cause of the problem, that's your right, since it's your money. But in the long run, spending a modest sum on basic diagnostic equipment that can be used on any car and learning how to use it is a better long term strategy than throwing parts at a problem and hoping for a fix. If you're not the DIY type and you just need to get past this at any cost, I get it. Just be aware that you're rolling the dice if you replace parts based on theory rather than solid evidence.
    – MTA
    Jun 22 at 12:15
  • My car was at the dealership repair shop for two weeks where they did repairs worth $1.4k trying to fix this problem, and it's still happening. Spending $20-30 for the part and changing it myself for free seems like a bargain. At worst, it won't fix it, and will be no worse off than before. I see no downside.
    – Ady
    Jun 22 at 14:32

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .