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Boost issues

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Old 05-07-2018, 05:04 PM
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Boost issues

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Originally Posted by Outlaw01
Good afternoon sir, been reading the forum for a few days and just joined today. I have a 2008 SS with only 54k miles on it. I I hereted the vehicle after my fathers passing and I have some questions about the cool little car. I have been driving it for a year now as a daily driver. The most boost I have ever seen out of the car is 8-10. Last Wednesday while driving to work on the high way I punched it to go around someone. The boost came up to around 8 then all of a sudden just completely dumped back to 0. The car nosed over and would not build boost at all anymore. Still runs fine no mis in The engine or anything like that just no boost. Since then it has happened several times and seems to rest if you will with cycling the key? It has also set the check engine light code was P0299 low boost. Car is completely stock other than a K&N airfilter. Not really sure why all of a sudden it started doing this. The fixes for the issue seem to be all over the place from reading the forum but wanted to reach out to someone that seems to be in the know and has spoken to a lot of people. Just trying to advance my learning curve. Not sure if I should just go they and replace the MAP sensor, the boost sensor and all the intercooler duct work and see what hat gets me or try and adjust the Wastegate to get up to the 14-16 lbs that it should have factory from what I can tell from reading different threads? Nothing looks easy which is fine but just wanted to make sure I cover it all if I have to pull the front of the car off the access the intercooler and ducting. I look forward to hearing back from you and being a part of the forum.

Thanks

jeff
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Old 05-07-2018, 05:06 PM
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Hi Jeff, to the forums!!

I think you'd want to start by looking for boost/vacuum leaks. Here is a link to a homemade leak tester, or you can have a shop test it for you.

https://www.cobaltss.net/forums/how-...ss-lnf-223319/

Do you have the GMTU (GM Turbo Upgrade)? The telltale is Bosch TMAP sensors, with a blue label. If you do, I would look at the lower sensor. These have been known to contact AC components, and the port on the sensor could be cracked.

This is a good start, I'll copy this into a thread proper, so that others can weigh in.

Last edited by RJ_RS_SS_350; 05-07-2018 at 08:19 PM.
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Old 05-07-2018, 05:36 PM
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Car has no upgrades of any type bone stock automatic car with literally an airfilter change.
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Old 05-07-2018, 06:51 PM
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Welcome to the site, check the clamps and tubes for the charge pipes and inspect the intercooler for any damage
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Old 05-07-2018, 08:27 PM
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All the clamps and tubes are tight no issues there. Will try and build an apparatus to pressure check the tubes coming off the turbo. Driving in today was running fine ran it up to 8psi (which is the max boost I have ever seen on the car in dr king it for a year) then all of a sudden the car nosed over and boost went to zero. Once it does that and you continue driving it will only go to 1-2 psi boost. Once I stopped. I turned the car off and restarted it. Then finished drive to work and boost was back. It did show a pending code of P0299 but didnít actually turn the Check Engine Light On. Once it reset is I keep it below 5psi it doesnít seem to trip again. Just have to figure out whatís causing it to trip all of a sudden. And then figure out why I only have half the boost that everyone claims the car is supposed to be set too factory.
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Old 05-07-2018, 08:34 PM
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All the vacuum lines, the vacuum tank, charge piping, intercooler, etc. This can be very difficult to diagnose. You could also check the diaphragm inside the bypass valve, see if it's damaged. This should help with that.

https://www.chevyhhr.net/forums/how-...acement-43763/

That's too bad the pics are all gone from that boost leak tester thread...
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Old 05-07-2018, 10:23 PM
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Yes, you have a problem.
Normal boost on a stock SS should be in the 14-17 psi range.
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Old 05-12-2018, 05:02 PM
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ok here is the update. I built a leak Tester as described in a link I received. Slapped it in and ran the boost gauge up to about 12psi indicated. Found my leak. The intercooler plastic tank is cracked. On the cold side coming out of intercooler to the motor. So now to look for an intercooler preferably all aluminum with no plastic :) also since the front bumper is off any other mods suggested? As far as intercooler duct replacements? Thanks for all your help guys I greatly appreciate it.
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Old 05-12-2018, 06:33 PM
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Here is a how-to that should help with bumper removal. https://www.chevyhhr.net/forums/how-...dlights-32354/

I removed my bumper to install muck collection tanks for my PCV catch can systems.

Some have changed their headlight assemblies to HID, or LED, or darker colored.
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Old 05-12-2018, 07:12 PM
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Looks like I will order the ZZP kit with the large core and duct work to match. :) and maybe some new lights :) if I can find matching fog lights. So that they all look the same. :) LEDs maybe :)
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