banditorama

I have supercharged my 2007 chevrolet HHR LS and since this it has been throwing a p0300 misfire code and idles very roughly. When I got the car back from the dyno shop the tuner told me the idle issues was probably because of the spark plugs. I gapped them in at .035 like the person from ZZPerfomance had said and the car still misfires. I then checked for vacuum leaks and found a loose hose which smoothed idle out a little but still misfiring only at idle. The car has 60# injectors and a 2.9 belt plus a new intake manifold from the cobalt, I don't know if maybe it has something to do with different airflow or something. The car runs great but I really want to get this problem solved because the car needs a retune due to a slipping clutch when I first took it in. I don't know maybe it could be the tune or the larger injectors, anyone have any suggestions?

SS fan

Welcome to the site !! Should be a couple guy's who might know around here somewhere.

American & Proud

First, Congrats on Supercharging your HHR.

Did you buy the ZZP Kit? Or did you piece your own together?

The ZZP Kit comes with 39 and now 42# injectors. So give us some more Details about your install.

I will be using 60# injectors on my install, and from what I have read they and the 80and up injectors have a tendancy of a little rougher idle. Takes more Tuning work to get them dialed in properly. Are your 60# injectors Flow Matched?

Alot of that Tuning time will depend on if your tuner actually has real experience tuning our ecotec motors With a Supercharger. A Tuner can have alot of experience tuning one type of motor or several, but if yours is the first one he's tried tuning 2.2 or 2.4 thats supercharged he's not gonna get it 100% on the first try.

He may know the 2.0 and say the 2.2, but Not the 2.4, if he lacks the experience with the motor you have it will take more effort on his part dialing it in.

As I said the bigger injectors have a little rougher idle in our application but he should be able to get it dialed in pretty good.

Get your clutch replaced with one that can handle the new HP or you'll burn up another oem one pretty darn Quick from what I have read. I have an automatic so I don't have that problem to worry about. Double check everything and have at refining the tune your guy started so far.

Lots on info on the Cobalt SS forums.

Hopefully the others that have supercharged their HHR's will chime in and give their thoughts as well.

banditorama

I have the zzp stage 2 kit and i'm not sure if the injectors are flow tested. Also I replaced the stock clutch with the stage 2 zzp kit. The car runs great outside of the idle problems I really think it's the tune cause he couldn't finish it but I want to be certain so I don't have to bring it back after the second tune.

Jon Bond

Did you get this fixed? A tuner should be able to tune the car for an idle. The programming for the idle PID's is separate from WOT and spark/fuel tables. Sounds like MAF table or fuel injectors are not dialed in.

Also, in my experience here at the shop- use a plastic zip tie on any vacuum lines that run to any intake port that is pressurized by a turbo/supercharger. Under boost, they will balloon up and leak boost out which causes air/fuel miscalculations.

prod

yeah from what I have read, the spray pattern on the 60# injectors is not optimal for our engines, makes it hard to tune for a smooth idle. 42# are easier and should have just enough flow for a 2.9" pulley.

Jon Bond

You are correct about spray pattern affecting idle. All readers should know when upgrading fuel injectors in multi valve engines require a split spray pattern with a 30 to 60 degree spray angle for good driveability and good fuel economy. This is often over looked and one of the largest tuning issues I have seen.