Jared Burton

Hello, so here's the deal. I have a 2008 Chevrolet HHR SS. Same engine setup as the turbo cobalt. I am posting here because not too many people do performance upgrades to the hhr's. The car is stuttering/stumbling when I go more than 50% throttle and the vacuum pressure on my boost gauge went down past 20, which is more than I've usually seen. Idle is also a little bit rough and gets worse when air conditioning is on. We used to live in MN when it was around 20-30 degrees outside and low humidity. This is where/when I got the car tuned. We now live in Florida where it is warmer and more humid. I don't know if it's maybe a mapping issue with climate change or what. I didn't start noticing the car acting up until after we went through the mountain areas of Denver, CO, once we got to lower elevation.

When I disconnect the battery to reset the ECU, the car takes a minute to start. After the initial start I don't have problems with starting the car.

Mod List:
zzp K04 turbo
k & n intake zzp
ported head
bigger fuel injectors
catback exhaust with 1 catalytic converter
zzp intercooler and piping kit

What I've Done Already: (No Check Engine Light)
Spark Plugs
Coils
MAF Clean
K&N Filter Clean

jdbaugh1

iTrader: (1)

So when you open throttle up past 50% the vacuum pressure on your boost gauge decreases? Or are you saying the boost psi is less than 20?

I'll ignore the above statement until you clarify because that would be very strange if you where reading 20 in-hg while driving and with the throttle mashed over 50% When you disconnect the ECU and it doesn't start as well until after it has ran 1 or two times that is usually a pretty good indication that your tune could be optimized a little better because most likely the improvement is from your computer adjusting fuel trims on startup. I think turbo HHR's have a stock wideband that you can read with rpd or some sort of OBD II scanner. Have you taken a look to see what your fuel is doing?

Jared Burton

No no I was just taking notice that my car was holding more vacuum than usually when at idle or deccelerating. instead of the usual 15-20 in/hg it's over 20, but that can be attributed to the elevation I believe because Florida is almost sea level. I just wanted to include it so that no stone was unturned.

I did do a fuel pressure test on the car and my pressure was a little low. So now I'm thinking fuel filter. This sucks because the filter is actually the whole pump assembly and I have to drop my gas tank to replace. Everything seems to be lining up with fuel filter as of now. The car does have almost 100k miles on it with rebuilt motor. I tried reading with scanners from auto shops but none of them have capabilities of displaying fuel pressures, just air/fuel ratio. My A/F is 15-16.

umrdyldo

iTrader: (1)

I was taking it as him saying it goes into vacuum greater than -20 in HG. I'm trying to think why that would happen though.

As said, we need to see your Fuel trims. LTFT, STFT. This will tell us if there is a vacuum or boost leak possibly.

Check all of your turbo charge pipes and check all vacuum hoses for leaks.

ECaulk

iTrader: (6)

Sounds like you need to do a boost leak, clean your map sensors and then get a new log at your new location in Florida. Then get any adjustments made needed to the tune.