Andrew30

Hello everyone. I've owned several performance vehicles in the past but this is my first turbo engine and I'm not very familiar with them. I purchased an 08 SS about a month ago. It has 110,000 on it and as far as I know is stock other than the GM upgrade. Sometimes while cruising at a constant speed, any speed, the boost will fluctuate like crazy up and down. More or less throttle and it stops. Doesn't do it all the time. Thanks in advance for any help.

RJ_RS_SS_350

Hi Andrew, to the forums!!

While cruising, you shouldn't even be in boost. The boost gauge also shows vacuum (less than zero part of the gauge), which will fluctuate with any change in load(slope, etc) although I wouldn't expect it to in the way you are describing.

Maybe you could catch it on video and post. You could check to see if there are any CEL codes stored, your local mechanic or auto parts store will be able to do so. Pay no attention to the code descriptions, just post up any actual codes here.

Do the RPMs fluctuate also? Do you have an auto or manual trans?

Andrew30

It's a 5 speed. Sorry left that out. It is fluctuating from 0 to 5lbs to 5 vacuum under light load. On my way to work today in 2nd the rpms where bouncing and felt like it was running out of gas. I let off and then accelerated and it built boost and was fine. No codes. Just wondering if this is leading to something. 95%of the time it's fine. When I first got it I put my foot down full boost and 10 minutes later got a code. Lean I think. Cleared it and fine since. Thanks for taking the time to hear me.

firemangeorge

Welcome to the site.

Sounds like you may have a leaking charge pipe or maybe an intercooler leak. Check the intercooler end tanks for cracks ( the stock tanks are plastic.)

Fwiw. I have both the pillar boost gauge and the RPD digital gauge.
Cruising at a constant 50mph, flat road, I will see about 10-12 into vacuum on the pillar gauge.

Also. Clearing a code doesn't fix the problem. You should retrieve the code # and find the cause.

Andrew30

Any advice on how to diagnose that. I have no problem working on engines but like I said turbos are completely new to me.

Andrew30

Just drove the car on lunch break. At first it studdered upon acceleration. Normal driving maybe 5 lbs boost. More throttle and it went to 10 lbs and cleaned up. Power seams to be delayed. Only way to explain it is feels like an on off switch. Lots of power or nothing. No in between.when it's good it's smooth through out.

donbrew

P0171? My guess is fuel pressure. Mentioning codes is very important info.

Andrew30

I don't have any codes right now. I cleared one right after I bought it. I put about 1600 miles on it since then.

donbrew

I moved your post to this thread, I suspect that's what you meant.

Not having a CEL does not mean there is no code stored. Knowing that you had a perhaps, transient lean code helps in diagnosing. Even an occasional code means something, there should never be one in a perfect world.

A lean condition can be caused by either not enough fuel (low fuel pressure) or too much unmetered air (faulty air piping).

Andrew30

just hooked up a scanner and had 2 stored codes P101 mass/volume air flow circumstances range/perf.....and P106 map/bar press circumstances range/perf. Any ideas? Supposedly the dealer changed a map sensor before I bought it. I appreciate everyone's help so far.Thank you