# Bizzarre random zero boost problem?



## obermd (Mar 3, 2012)

First, some base info on the Cruze 1.4T MT drive train. The Cruze is a torque controlled drive system so having low or no boost is normal. Also, full boost doesn't come on until 2500 RPM and then only if the car needs it to respond to the throttle input.

However, you're describing a lack of power and it certainly doesn't sound right. If you can take it in when it's doing this but don't turn the car off. Have the service tech drive it so he can feel the difference between the car not having boost and after turning the car off. You didn't say where in Colorado you are but if you're near the south side of Denver give Ed Bozarth Park Meadows a shot at it.


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## obermd (Mar 3, 2012)

I don't know if you've tried MedVed in Castle Rock, but years ago they finally diagnosed an fixed a 70,000 mile stalling problem in my wife's Dodge Intrepid. I don't know how their Chevy service is but based on your location and my experience it would be worth a shot there. Whatever you do stay away from Daniels Chevrolet and anything owned by Will Perkins.


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## originalkontrol (Oct 30, 2014)

Thanks for the ideas, obermd. 
"First, some base info on the Cruze 1.4T MT drive train. The Cruze is a torque controlled drive system so having low or no boost is normal."_ 
I've never heard of this type of thing... Low or no boost is normal? Is there somewhere you know of I can learn more about this system?_
As far as the dealer goes, I went to Al Serra north, but I will hit up ED Bozarth tomorrow! No Perkins or Daniels, HEARD. Medved...eh, I had a very simple issue with an 03 Dodge Dakota a few years back, and they were one of three dealers I took it to, even told them exactly what the problem was, and all 3 times I was told they could find nothing. Then I finally explained to the last guy how to properly check for the problem at which point they were like "OH!... yeah, sorry". But I won't hole that against them. I figure the more people I ask about the issue, the more likely i am to find an answer! Thanks for your ideas, and again if you could direct me toward some info about the Torque controlled drive system, that would be most excellent! 
Cheers,
Erik J.


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## obermd (Mar 3, 2012)

Tell the service advisers at Ed Bozarth I sent you.

The ECU in the Cruze manages the turbo boost levels to maintain the torque needed to maintain speed or accelerate. When decelerating you are literally running with zero boost in this car. We've seen this multiple times when people get Trifecta or VTuner performance tunes and discover they get nowhere near the 20 PSI boost those tunes promise. If the car doesn't need it the ECU simply doesn't spin up the turbo to provide it. What you're reporting is one I don't remember seeing before and makes me suspect there may be a sensor going out.

Mike.


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## Slammed2014Eco (Feb 13, 2014)

Yea, I've never experienced the issue that your having so that's odd... most I've had is when I get on it the turbo hiccups almost then reboosts lol


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## originalkontrol (Oct 30, 2014)

Thanks guys! Obermd, I will def check out Bozarth and let them know you sent me! As far as I know, my car is totally stock (for now)... I kind of thought the car might monitor/adjust boost depending on need... It does seem to sort of undulate a bit under medium throttle... I just assumed this might be normal? Oh goody sensor issues! LOL, I suppose the thing that surprises me the most is that for such a major change from the motor, no cel's, weird.
Slammed, maybe we're getting similar undulations under medium throttle?


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## Slammed2014Eco (Feb 13, 2014)

Yea, I've noticed it hiccup or medium to heavy throttle. The tune that I have has helped with that a bit but it does still happen from time to time.


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## spacedout (Dec 7, 2010)

What octane fuel you running? When I run 87 octane regular on hills I can feel the car detune itself to the point I'm starting to loose forward momentum even down shifting a few gears. Usually when this occurs though its pretty obvious, you can see the tach drop more than a few hundered RPM and if monitoring the torque app, knock is occurring at the same time.

Doesn't happen every time, though enough I will never run less than midgrade again. My car runs its best on 93 octane with 10% ethanol which is a bit hard to find in my state. Most stations here offer 91 octane no ethanol as the premium grade. Sure 91 is better than 87 on hills, but no where near as good as 93.


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## Slammed2014Eco (Feb 13, 2014)

All of us in colorado run at the max of 91 that I'm aware of, we don't get 93 here =<


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## obermd (Mar 3, 2012)

Definitely run 91 in Colorado, even in the winter. Also, I wonder if the undulation you're feeling is DFCO. Do you guys feel it on downhill runs?


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## spacedout (Dec 7, 2010)

Slammed2014Eco said:


> All of us in colorado run at the max of 91 that I'm aware of, we don't get 93 here =<


Higher altitudes don't need as high of octane, that's why you guys also have 85 octane regular.


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## obermd (Mar 3, 2012)

The Cruze will NOT run on 85 octane, even in Denver. I've tried both it in both my ECO MT and my son's LS MT. He thought his car needed service - I didn't tell him.

If you search you can find 93 in Denver - it's just not real common.


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## spacedout (Dec 7, 2010)

obermd said:


> If you search you can find 93 in Denver - it's just not real common.


Using google I found quite a few forums with people listing stations in Colorado with 93 octane, however most of the posts were quite a few years old. 

From my understanding of how elevation effects octane requirements, 91 should preform as good as 93 at your elevation. I believe the reason for less octane required at altitude has to do with lower barometric pressure causes less heat in the cylinder when compressed. From another website:* Altitude - pressure, 14.7 psi at sea level, 12.2 at Denver (5,000 feet) 10.1 psi at 10,000 feet (many Colorado passes are 11,000 feet) 8.3 psi at 15,000 feet (Colorados highest roads are just over 14,000)
*
However how does the turbo effect this? Would think it wouldn't need to boost as much to create the same amount of power as at sea level(the torque limiting the stock ECU does), but the boost pressure the turbo adds seems the engine would act more like it was at a lower altitude & require higher octane than most other normally aspirated cars in your area. Think the cruze 217-220F normal operating temps probably also have some effect on the octane requirements.


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## obermd (Mar 3, 2012)

The Cruze's 1.4T is actually more efficient at altitude, especially on the highway. The ECU can compensate for the lower atmospheric pressure up to somewhere over 11,000 ft by increasing the boost from the turbo. Based on when my ECO starts gasping for air the turbo (stock tune) maxes out around the tree line (11,500 ft in our central mountains (I-70 on the north and US 50 on the south).

As for fuel economy anything above 4,000 ft or so seems to improve highway fuel economy by reducing the aero-drag on the car. I actually get 1-2 MPG better fuel economy running on Cruze control in Colorado than I did in NY and Pennsylvania at the same 65 MPH. On the 500 mile round trip from my house to Grand Junction and back I average ~47-48 MPG. Crossing PA and NY last summer I averaged ~46-47 MPG. The average speed is actually a little higher on the Grand Junction run as there is a 35 mile stretch of 75 MPH highway with the rest being 65 MPH. The 75 MPH stretch is a relatively constant sloped elevation change from 6,000 ft at the entrance to Glenwood Canyon on the west and 7,500 ft at Avon on the east.

The drawback is that we have slightly less off the line power until we spool the turbo.


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## jblackburn (Apr 14, 2012)

Knock causes the car to dump off boost (slammed14eco). These engines knock a LOT, even on 91 octane.

As for the OP...I really have no idea. What you describe isn't normal; the car is severely detuning itself for some reason...probably sensor-related, but whether it is knock sensor, cam phaser, airflow-related, I have no idea. If you can cause it to happen on a fairly normal basis, a couple pulls with a dealer scan tool (maybe ask to go for a ride with a tech) may show them something to look at.


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## Slammed2014Eco (Feb 13, 2014)

Odd, I thought finding 93 octane here was like finding e85 lol. I've seen very few places that have either and they are typically in between the large cities I know there are 2 places in between denver and colorado springs that have e85 but I've never seen 93 since I've been here 5 years now. I've heard these cars do knock a lot so that's not really suprising I'm assuming that it loses that boost for a second to compensate for the knock?


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## jblackburn (Apr 14, 2012)

Slammed2014Eco said:


> I've heard these cars do knock a lot so that's not really suprising I'm assuming that it loses that boost for a second to compensate for the knock?


Yeah, it opens the wastegate and dumps it off. Builds again very quickly because the turbo's so small.


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## obermd (Mar 3, 2012)

OP - any update on your boost issue?


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## originalkontrol (Oct 30, 2014)

Haven't figured it out yet... Went to Ed Bozarth, and explained the issue. Greg said he's never heard of that with anyone else. He offered to make me an appointment, but I now that it has happened twice with similar circumstances, I'm going to see if I can intentionally reproduce it, and maybe even get it to the dealer while it's not boosting. Also have a friend who is going to let me borrow a scanner that you can run while you're driving and can actually record 30 seconds of live data and play it back. goes through all the things the computer and sensors are doing. Hopefully that will give me some ammo and direction for the service guys to use. But either way, I'll def keep you guys posted!
Cheers!


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