Hoping someone has so insight that can help me track this down...
Has 118,000 miles only on cold starts it will crank a long time them when it starts it sounds like it's running on 3 cyl's for perhaps 1/2 min. then it smooths out. Other info... no codes other than I did get a rich mixture code that I cleared 2-3 weeks ago but never came back. I am running standard Speedway or Sam's Club Regular gas I assume to be about 10% ethanol but Torque reports the ethanol mix to be 40-47% over the last 5 fill ups. Also it reports the long term fuel trim to be -14+%
I changed plugs (old AC-Delco's had about 40k on them and they all looked good no odd coloration) now trying Bosch +4 plugs --- It made no difference

#4 plug had oil to the top of the hex from when the fill pipe fell off and top of the motor got covered with oil splashing out the valve cover. cleaned that coil and reinstalled it no change. tried a new coil in # 4 It made no change either.

It has 2x times failed to start. later after letting it sit and using WOT it started. (I am assuming it flooded because of the long crank time).

I have installed a new upstream O2 sensor. It did not make any difference.

Once it has ran for a Min or so it's fine and does not seem to be low on power but the fuel mileage is down about 5-6 MPG HWY from normal

Does anyone have any suggestions?
Thanks
Dave

 

Welcome to the site

I would first check fuel pressure. Make sure it holds rail pressure. ( rail pressure with engine not running)

You may have an injector leaking down and can cause a flooded condition when starting cold.

There are other thinks like the fuel vent solenoid or canister purge solenoid that can make some strange symptoms.

 

How old is the air filter ? Could be clogged
Clean the MAF sensor , use sensor safe cleaner
Clean the throttle body, use throttle body cleaner
And yes check fuel rail pressure could be a dirty fuel injector
Please use the search window for instructions on how to do these tasks

 

Codes tell you things. Vac leaks can take weeks to get tested by the computer.
My money is on the purge valve. The one under the hood. That can make for hard starts and rich/lean codes. Bt the MAF can do the same.

 

Thanks for the idea's !!! Cleaned the MAF a couple of weeks ago. Air filter has under 10k miles and still looks clean/ can see light thru it. Will try the rail pressure test and cleaning the TB. and see what happens. Probably be a day or two to get time to try them and see what happens.

Then if still no change will try the purge valve. Also going to try gas from the top tier dot com stations to see if that changes the ethanol % or help with the starting. I know it's the DI motors that the gas makes a big difference with deposits on the valves but still confused why I am showing 40+-% ethanol....

 

Give this thread a read. Maybe not exactly your problem, but an interesting read. https://www.chevyhhr.net/forums/prob...e-after-43987/

A FYI. There have been previous posts that state HHR engines don't really like non- AC Delco plugs. Safe bet is to use the factory AC Delco Iridiums.

 

The plugs that came out were the AC Delco Iridiums. Did not notice a difference with the Bosch +4's but was going to look at them when I replace the air cleaner bracket that broke by the #1 exhaust... My thought process with the +4's was that the plug gap is not shrouded like the AC Delco Iridiums by the side electrode. That post was a most interesting read. Makes me wounder what would happen with a few tanks of E85??? then go back to the Top tier gas? would that perhaps force the ECU to re think it's fuel maps???

I am going to wait till the weekend to check out the ideas.... (it's only 3 deg out LOL).

Will post what I find when I look at the plugs and look at the other ideas fuel pressure ect...
Dave

 

My reason for the comments about sparkplugs. There have been posts on here before about people having issues with the non- AC Delco plugs. I recall things from running bad to even Check Engine lights coming on after a plug change.

Many of these were fixed by going back to the factory iridiums. It seems the Ecotec engines were designed around this type plug. My opinion is, best to stay with what works.

 

X2 what Firemangeorge posted I have tried those Bosch plugs changed them out after just 3,500 miles

 

I've been having this same problem with my wife's 07 for a while now. Seems like a bad fuel pump, but I changed that, I changed the purge solenoid, still doing it. Just replaced the engine over the summer and cleaned the throttle body, so that's not it. I guess I'll clean the MAF next and see what happens. Although, fuel pressure was dropping to around 20 over a 12 hour time period. Never thought about a leaking injector