Weird Boost Issue with LNF

[JAHSMITH]

I've seen people complain of this issue before and I am wondering what the relation is.

Last night while cruising I ran into a problem where the car wouldn't boost over 5 psi. Everyone references cracked end tanks, boost leaks...etc but this isn't the case.

Last night, I held a pretty high rpm cruise speed (4000 rpms) with moderate load (40% throttle) for about 1 minute straight and noticed what felt like a decrease in power suddenly. ( No limp mode lights or anything)

I Let off the throttle and laid back into it and the car struggled to boost up to 5 psi no matter the gear or load. I've seen this one time only previously and it was caused by the same driving style.

I turned the car off and back on and the problem was still present. The reason I don't believe it to be a physical part issue is because both times I Simply pulled over to the side of the road and re flashed the car and the problem disappeared. any LNF guys have any insight to this issue?

[Lazyunionworker]

You can throw a code and not have the light come on. You still need to hook it up and check for codes like under/over boost codes etc.... It takes something happening for 3-4 seconds continuous for the computer to register a fault. Boost leak test it, check nut on waste gate arm(this loosens), vacuum hoses, all the basics. After that, log the car and post it. The two nuts on the waste gate is my best guess at this point. They like to back off. GM fixed this with a little retaining clip when people went in for under boost issue. You have to jack up the car and do all checking/ fixing from below. Hope this helps.

[JAHSMITH]

I've checked no codes and car is holding 20 psi to red line. Also literally after I reflashed the car the problem stopped and hasn't happened again since. There has been 60+ miles and multiple full boost runs 2nd - 4th and no problems.

[Lazyunionworker]

Run it in 3rd and slowly push into it. Between 3000-4500 it will fall on it's face and not go over 5psi. When the fault happens after 3-4 seconds of continuously causing the fault and the computer will put you into limp mode. The engine is using more air than the turbo can provide at that point. 1st and 2nd gear are fine because you shoot by the troubled area/lack of boost so fast. Turn the key off and back on and all is normal again. 1 in 20 times it will actually throw the p0299 under boost code. I battled this problem when I first got my car. Jack the car up, put jack stands under it, get two 10m wrenches, a light, a pair of small hands, read the threads on how to properly adjust the waste gate and do it when it is COOLED OFF. Tighten it a few turns towards the waste gate canister, tighten the nut on the inside, go test, repeat until the turbo supplies enough air to make the engine and tune happy. These are notoriously miss adjusted out of the factory and also vibrate loose. Hope this helps.

[Lazyunionworker]

http://www.chevyhhr.net/forums/attac...5&d=1281714301.

This has a pic of the retaining clip.

[codename Bil Doe]

That was old school tuning trick before hpt unlocked the pcm. People would adjust the screw for more boost. If some works, much more must work better. Maybe done by po?

[Lazyunionworker]

It would have been great if I was doing that to get more boost, but it was a bastard to figure out what was going on when it happened to me. I had to custom bend a 10m wrench to get up in there and three times to get it dialed in right. After all that...three weeks later the nut vibrated loose again. Thus, I ordered the $3.95 retaining clip as not to ever have to do it again. It was a learning experience. Lol

[califcarm]

Has the problem stayed fixed?

I have run into a P0299 3 times now recently without anything I can see wrong in the logs. Might be physical, but seems after going into limp mode it will run through some gears fine (2nd and 3rd, but then do it again after a while). Just wondering if yours is still good after a reflash?