Needing a tune? - Chevy HHR Network


2.4L Performance Tech 16 valve 172 hp EcoTec with 162 lb-ft of torque

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Old 02-02-2017, 07:52 PM   #1
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Needing a tune?

I have a 2007 chevy HHR 2LT 2.4L Automatic.

I have a K&N intake and a gm performance exhaust made by borla, but I changed the muffler to a dynomax vt for drone reasons.
(which is basically the same as having all gm performance parts that they offer from the dealership)

The car is great, no problems, but...

I was looking under the car today and noticed all of the stainless steel is black!!!

After a quick google search, exhaust turning brown or black may be a sign of a car that runs rich.

Can the added intake and exhaust made the car run lean but then the computer compensates and instead makes it run too rich?

Could this be the cause in my case? and if so how can I fix that?

Is it a sensor in the intake or exhaust that is going bad, or does some type of tune up need to be performed?

Is there a such thing as a dealership dyno tune that can be performed to adjust the computer to the upgraded parts?

Or does that just happen to stainless steel? This is the first time I have had a stainless exhaust.

Please let me know, thank you.
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Old 02-02-2017, 08:29 PM   #2
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I didn't see any results that said that running rich causes what I think you are describing. A rich fuel mixture would cause the tailpipe, or the tip, to turn black with soot. And would likely throw a code.

Stainless turning a light brown, from heat, could be normal. If it's black, it sounds more like an oil leak is distributing itself onto the exhaust parts, then baking on. It could also possibly be road grime baking on. But mostly oil.

Kinda like when you crack an egg on the edge of a stainless frypan, and some of the eggwhite trickles down to the underside, baking on, and not getting much attention when it's time to clean.

Stainless steel won't easily rust, but if you want it to stay pretty, it needs to have the contaminants cleaned off regularly. Easy to do on a frypan, not so much on the underbelly of a car.
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Old 02-02-2017, 08:39 PM   #3
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well when looking at it it is uniformly discolored. The resonator and muffler and short steel pipe I had to add by the muffler are all still shiny silver color.

The exhaust tip is shiny stainless on the outside, but if i want it to shine like new I have to clean off the black dust coming out from the inside and surrounding the edge.

I feel like it is baking and the discoloration is happening due to heat?
Possibly because of a rich mixture being burnt off???

No check engine light!
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Old 02-02-2017, 09:30 PM   #4
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The inside of the tailpipe tip on my SS stays black and sooty. Clean it and it will soot back up in 100 miles.
If you have soot collecting on the outside of the exhaust, you've got an exhaust leak.
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Old 02-02-2017, 10:27 PM   #5
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well its not oil, and its not soot on the outside.
Its blackened 304 stainless steel?

I mean shiny stainless 304 to now black pipe, its dark and I don't think it can be polished back to shiny.
I have a 1,000,000 mile warranty on it, but need to know if its the car causing this, catalytic converter, or indeed an exhaust defect?
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Old 02-02-2017, 10:44 PM   #6
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I don't know how its running??? There is no codes on the vehicle, no pending codes, nothing.

Apparently running lean causes the exhaust temps to be incredibly high, so I don't know if its lean causing burnt exhaust pipes or rich causing black soot on tip.

But as of right now I have both of those things happening.

I guess I will be pulling the plugs to check the condition, but other than that... it's either spending $100 for a check up at the dealership, or just buying all three oxygen/air sensors in the intake and exhaust for the same price?
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Old 02-02-2017, 11:16 PM   #7
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Here is a picture of the pipe color.



Here is a picture of the steel pipe section and burnt area on the muffler.



I know the joints need tightening but those areas are all behind the sensors.
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Old 02-03-2017, 10:31 AM   #8
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Looks like normal heat discolouration of a stainless steel exhaust, if you want it shiny and mirror bright, then you can't drive it , just show it!
Now , I know you bought your HHR and modified it with the intake and exhaust to keep it clean and drive it , so here my creedo, if you can't see it whilst driving , it's just fine!! Pedal down and enjoy!
My pipes are Walker SS and they are the same disappointing cruddy looking burnt, but they do their job!
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Old 02-03-2017, 10:55 AM   #9
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Well ok then, sounds good to me! :)

I will still pull the plugs and have a look, just to be sure.
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Old 02-03-2017, 11:27 AM   #10
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Remember, don't try and gap them or even check the gap!
While you have your hands dirty, check the hose from the valve cover to the elbow at the throttle body for oil and oil being sucked into the throttle body
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