Plugs all looked lean if anything except for 4 it was carboned up a bit like running rich, but not fouled., also I for got to mention I tested commpression and got: 155 on 1, 150 on 2, 125 on 3, and 120 on 4. and I have not actually been a technican fo cars since 1997, so I may be overlooking something, but not much.

 

Does that 35 psi spread between cylinders 1 and 4 seem normal to you? Or is the pressure bleeding off before you read the gauge?

 

Well, I have the factory manuals and they state that there should not be more than a 70% difference from highest to lowest. They also state that they should be above 100lbs. 70% seems real excessive to me not to mention 155lbs vs. 100 lbs. But to answer your question, yes that is excessive spread for an engine that has been meticulously maintained with only 37750 miles. unfortunately the lowest is 120 which is well above the manuals standard. These readings were also taken with the engine at operating temp. I stopped the engine, immediately removed the air cleaner assy and plugs and checked compression.

 

My 07 LT 2.4L has had its share of the 304 codes. Dealer replaced the sparkplug once but it came back after a couple of days and would go away after a couple of days. The mechanic told me if it was the injector it would be doing it all the time. Funny thing is it got better mpg with the check engine light on than when it was off. I was very late one day and I ran the crap out of it. Pushed it up to the red line several times during the 19 mile trip home. I guess that fixed it because it has been about 6 weeks now and no light. It is also getting getter mpg with the light out, although I have never got the high mpg some on here say they are getting.

 

Yep Ive replaced all the plugs. Glad to hear yours is gone. Mine was real bad and was constant all morning to work and to the dealer. My mil has also started flashing, which means it is disabling the #4 injector to protect the catalytic converter from meltdown. I just took it in so we will see. I will be real interested to see what they say. I gave them my last filter with some of the metal shavings that one bulletin says is normal due to the engine casting process. I also told them about that I have tried swapping injectors, coils and flushed the fuel rail 5 times and taken samples of the fuel, non of which had a pinhead of water. I also told them about the compression readings and that all the voltages and resistances to ground for the coil and injector connectors checked out good.

 

Well, Just talked to my Service adviser. They have determined it is a bad exhaust valve (or crack in the head) on 4. Seems like I was on track with the low compression. I told him that they might want to check #3 too. He said they will check them all once the head is off (I was hoping he would say that). He will get back w/me tomorrow with more details and a GM rental. Looks like it will be covered under the 5yr 100 k mile power train warranty. Thank GOD fer that. I will keep y'all posted.

 

Just talked to the chevy house and #4 cylinder was bad exhaust valve and seat. # was going out too. He said that they have a new tech that just came over from Saturn. He has done 3 of these on Sats. I asked If this was common and he said that the saturn guy had seen several. Bummer. I hope it lasts after the repair.

 

I have a 2007 HHR. Love it.
Check engine light came on about 5 months ago. Diagnosis meter showed "Misfire Cyl 2."

Changed the plugs, cleared the memory, and the check engine light went out for about 2 months. Then I switched the coils for cylinders 2 and 3 around and cleared the memory to see what happens. The "Misfire Cyl 2" code appeared again within a few days.

I just changed the injector for cylinder 2 and cleared the memory again. Started and idled it for 15 minutes with no check engine light. Will wait to see what happens.

My problem with the check engine light being on is my gas mileage dumps and there is a noticeable loss of power.

 

My 07 2.2 had the same code. Tried all the remedies fellow posters said. I ended up taking it to the dealer and they determined it was bad valve guides in cylinders 2 and 3. Replaced under the powertrain warranty.

 

Nice to hear good news once in a while