P0300
Secondary DTCs: P0036, P0054, P0128, P0141, P0455, P0442

C0292-1A
C0040-00

We replaced air filter and added Seafoam to fuel, which is presently E85. The dashboard temperature gauge doesn’t work. There is a tear in the air inlet hose to the air filter.

 

You need a new #2 O2 sensor
A new ACDelco 131-158 thermostat. That part number only. That is why the gauge doesn't work.
A new EVAP vent valve
Possibly check for a rust hole in the EVAP tube in front of the driver side rear tire.
New front hubs. Maybe somebody disturbed the right front ABS wire during the brake work.
There is some problem between the EBCM and the ECM, probably a wire connection
Don't agonize over the torn air hose, it can be repaired with metal duct tape or replaced with 3" (I think) vent tube from HomeDepot.
The P0300 is probably a product of all of the above.

I don't know what they think is the difference between primary and secondary codes;.Codes are classified as current, pending or stored/historic.

 

After buttoned up and driven about 15 miles, it started running very poorly, like it is on three cylinders, and stalling at intersections.

 

I agree with the frequent advice to not attempt to gap them. That requires some force. The iridium center wire is a bit brittle. But unless you're really ham-handed, there should be no problem gently probing with a wire or a thickness gage. And checking the gap of old plugs might provide a clue of HOW old. The electrode does erode, albeit slowly. The last set I changed, unknown age, looked pretty good, but the gap was well over spec, though I don't remember how much.

The tuner crowd gaps those plugs, reducing it apparently to prevent blowing out the spark at 30 psi boost, lol.

Also, I just got delivery on a set of 109's for a non-HHR (LTT V6 if anyone cares.) No sleeve to protect the gap if bumped. (Hope they're not counterfeit.) I will be checking the gap.

I saved some old plugs. Now I want to try to gap one and see how easy it is to slip and break it.

 

I have a plug in the garage with a very gently broken whisker. I keep it as a reminder. Touching it was enough to break it.

 

We replaced the spark plugs today with the recommended AC Delco Iridium plugs. From my phone, I will add a photo of the plugs removed.

 

Is it running better?

 

Shoul be, those are not recommended plugs and this photo shows why

 

Definitely running better on the AC Delco Iridium plugs!

Thanks for the advice. Start to finish only took one hour.

 

Those were waaaay overdue.
Is coolant disappearing? The second plug looks steam clean. The first one may have been loose