RomeDiggy

This problem just started the other day. The turbo is boosting when im bairly on the gas and then it will drop real fast then boost again without any change in throttle. I have no CEL. Should I take it to the dealer? Please help. I think the waste gate is closing too soon or vice versa not sure

09CobaltSS1

It sounds like the MAP sensors possibly aren't registering the boost correctly. Try cleaning them both with a electical parts cleaner. If that doesn't work then they will most likely need replacing.

RomeDiggy

I'll try that and see if it works. Ive only been GMS1 for a year cant believe that the MAP sensors would be bad allready.

09CobaltSS1

Yeah they can get gummed up with oil residue pretty easily which over time can ruin the sensor. Definitely try cleaning them both first before buying new ones and go from there.

Chevycobaltss3

iTrader: (2)

U would be amazed^^^^

09CobaltSS1

Yeah you're definitely right. There's definitely been quite a few of the 3bar maps failing, but he might as well try the cheapest route first before assuming they are bad .. ya know?

tomj77

iTrader: (2)

u sure ur not moving ur foot down a little? have u been driving more than normal aggresivly lately?

09BlueBaltSS

I'm surprised you made it that long without having problems

sick_tight

yeah, i had the issue with gummed up sensors after maf cleaner they worked great. designing a catch can for ***** and giggles now to try and prevent it but i heard that valve blow back is also an issue though

RomeDiggy

I havnt been driving any different. Its weird, I can feel it boost then stop boost then stop. WOT it doesn't do it, only at low boost

slowbalt84

put a bigger turbo on

Boosted4

RomeDiggy

Its not holding boost, I'm leaning towards BPV or waste gate acuator

slowbalt84

fyi i believe there was a tsb on the wastegate actuator

RomeDiggy

Do you have a link to that tsb?

Permafried-

Service Information 2008 Chevrolet Cobalt | Cobalt, G5 (VIN A) Service Manual | Document ID: 2206771
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#PIP4520: Low Boost / Power And/Or DTC P0299 Or P0101 - keywords actuator boost CAC charge control cooler driveability DTC ECM engine gas lnf low maf MIL reduced reducedpwmde SES wastegate - (Nov 4, 2008)


Subject: Low Boost/Power and/or DTC P0299 or P0101


Models: 2008-2009 Chevrolet Cobalt SS Only

2008-2009 Chevrolet HHR SS Only

2007-2009 Pontiac Solstice GXP

2007-2009 Saturn Sky Redline

With Engine RPO LNF Only




--------------------------------------------------------------------------------

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
A technician may encounter a vehicle with a low boost/power condition and/or DTC P0299 and or P0101 setting. This may be the result of a cracked or broken fitting at the turbocharger assembly.

Recommendation/Instructions:
It has been determined that the nipple for the turbocharger wastegate actuator may be damaged causing this condition. If this concern is noted please inspect the area on the underside of the turbo compressor housing for the wastegate actuator solenoid valve. The nipple (see CALLOUT #1) may have been damaged causing a loss of boost pressure. It may be necessary to remove the charge air duct for a closer inspection. See eSI "Turbocharger Wastegate Actuator Replacement" for solenoid replacement procedure.



This solenoid is available separate from the turbocharger and should be replaced as a sub assembly. Do not replace the turbocharger assembly.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION
© 2009 General Motors Corporation. All rights reserved.

Permafried-

There's also this one:

Service Information
2009 Chevrolet Cobalt | Cobalt, G5 (VIN A) Service Manual | View All Bulletins | Document ID: 2312877
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#09-06-93-004: Intermittent MIL/Check Engine Light On, DTC P0299 or P0234 Set (Adjust Turbocharger Wastegate Actuator) - (Jul 21, 2009)


Subject: Intermittent MIL/Check Engine Light On, DTC P0299 or P0234 Set (Adjust Turbocharger Wastegate Actuator)


Models: 2008-2009 Chevrolet Cobalt, HHR

2008-2009 Pontiac Solstice GXP

2008-2009 Saturn SKY Redline

2008-2009 Opel GT

2008 Daewoo G2X

with Engine RPO LNF and LDK (Europe)

Please Refer to GMVIS




--------------------------------------------------------------------------------
Condition
Some customers may comment that the SES light is on. Upon inspection, you may find DTC P0299 (Turbocharger Engine Underboost) or P0234 (Turbocharger Engine Overboost) set.

Cause
This condition may be caused by a mis-adjusted wastegate.

Correction
Note: The wastegate adjustment is sometimes a very fine process. When adjusting the wastegate, only small adjustments should be made. Loosen one nut at a time and only adjust the nut one turn at a time; then tighten the other nut against the shaft and test drive to verify. This may have to be performed several times to achieve the desired boost level. To ensure proper adjustment, the vehicle should be at full operating temperature when testing. The vehicle will be very hot and may need to cool between adjustments. Too large of an adjustment can cause repeat DTCs.

Adjust the turbocharger wastegate. Refer to Turbocharger Wastegate Actuator Adjustment in SI.

Troubleshooting Tips for DTC P0299 - Turbocharger Engine Underboost
To increase boost, adjust the nuts (in) towards the actuator; in essence making the shaft shorter.

Troubleshooting Tips for DTC P0234 - Turbocharger Engine Overboost
To reduce boost, adjust the nuts (out) towards the end of the shaft; in essence making the shaft longer.

Warranty Information
For vehicles repaired under warranty, use:

Labor Operation
Description
Labor Time

J5799*
Turbocharger Wastegate Actuator Adjustment
Use Published Labor Operation Time

*This is a new labor operation number. The next update of the Labor Time Guide will contain this number.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION


© 2009 General Motors Corporation. All rights reserved.

RomeDiggy

Well just got back to my house and got the balt out of the garage. Now its holding boost fine no problems. When it wasn't holding boost yesterday, I was doing a lot of 2nd and 3rd gear pulls.I'm think that the stock BPV is crap when it gets really hot.

80vetteL82

Sounds like some of the many symptoms I was getting the first time my GMS1 MAP sensor went bad...........and the second time my GMS1 MAP sensor went bad