843de

With those readings, and the condition of the plugs, I'm beginning to suspect the misfire is due to a failing injector. So I'd skip the leakdown test for now.

The GM tech can verify it with a scope, weak injectors will give themselves away with odd waveforms like the lack of a good "pintle bounce", or delayed firing.

Now if you're extra lucky, the new plugs may clear things right up.

silver2LT

I was quite happy with those cylinder pressures, I was really expecting the worst. Previously, The miss occurred after swapping the coil pack within several minutes of idling with the AC on - after the compression test and ultimately putting new plugs in, the misfire monitor ran and completed. I had the HHR running almost 30 minutes with the AC on yesterday but I can't call it fixed yet, I haven't even had it running long enough for the evap, and the rest of the emissions monitors to complete.

I will keep a close eye on it, my wife drives the HHR mostly but we'll have to swap this week.

I mean I've ruled out just about everything but the injectors themselves, so if it returns I could either put them on my cleaner rig I built a while ago or just get 4 new ones, they're not real expensive as they go.

Thanks again folks

donbrew

My eyeball said the gap looked a little too big, could be just my eyeballs.

sleeper

silver2LT-
fwiw: generally with worn valve guides, you can notice oil burning smoke out tail pipe at idle, or right after slowing down to idle & then accelerating..

Vacuum is greatest at idle. It will suck oil down the guides if they are out of spec.

I don't think guides are the issue here..

But the wet / black you mentioned may be over-rich fuel carbon. Hopefully it is not oil.

silver2LT

Surprise! Took two days but the miss returned for cylinder 4. I've just gone ahead and ordered 4 ACDELCO 2172907 injectors and hopefully can just be done with it.

A little odd though, cyl 3 and 4 both look sooty; the fuel feed line comes in directly next to the 4th injector, and next to that, the 3rd wonder if debris is clogging them up or something... I'll have to check out the inside of the rail when I have it apart.

And just for my own info - can't the valve(stem) seal take some lateral movement if the guide was wearing poorly? in which case you "might" not see oil burning ?

thanks

sleeper

Yes, that is true. A comp test won't detect worn guides..

Leak Down test will, 'if' that were the case..

Hope you have the fix.. Sooty doesn't sound like a clogged injector. nome sain.

silver2LT

I was tending to think the soot was due to misfires.

I've got all 4 injectors replaced. I also noted (through the injector holes) that the intake valves for 1 & 2 are very clean and 3 & 4 had wet-ish deposits on the umbrella part of the valve just above the seat(but still relatively clean). The valve stems were spotless and there wasn't any trace of oil anywhere. Certainly no evidence of oil leaking down the valve but the engine never burnt any anyway.

Another thing of note is I had RUST in the fuel rail which I believe caused all this likely. Everywhere something was brazed to the rail, rust was present. For example, there was rust on the inside where the schrader is brazed, rust where the end cap is brazed and although I didn't see it, I'm sure there was rust in the dampener chamber. I spent a good while soaking the rail in evaporust, then brake-cleaning it out and reinstalling it. Looked pretty good inside once I was done with it.

Immediately the engine ran with a smoothness I hadn't seen in a while and a CONSIDERABLE amount of vibration I had previously was gone.

Been driving it for 3 days and so far so good. All monitors are complete and ready. I'm going to start adding MMO to the fuel in this vehicle like I do some of my others. (It's really the only "additive" I believe in)

So, hopefully that'll do it - it's looking like it's fine now though at least thus far.

Thanks again folks

843de

Rust, well I'd like to say that I'm surprised by what you found as the root cause of the misfiring.

Unfortunately with the known hygroscopic characteristics of ethanol, I think this may be the direct result of running E-10 gasoline which is hard to avoid.

When possible, I do go out of my way to purchase "real gas" AKA non-blended fuel, just because of residing in the humid southeast. E-10 gasoline will attract and capture approximately 50% more atmospheric moisture than un-blended fuel.

In the future you might seek out un-blended fuel in your area, or consider a monthly fuel system treatment. I use Chevron Techron fuel system cleaner every fourth tankful.

silver2LT

You and me both, but while I do believe Ethanol likely played a massive part and I hate the the fact that it's in our fuel, I think the manner in which it's driven played a pretty substantial role too. It's only driven 6mi a day in town during the week and sometimes on the weekends. It often has a tank of fuel for a week or more. I am in NJ where I do not believe there are any "real" gas stations available. I have a Sunoco card and fuel all my vehicles there for that reason.

As for additives, I still don't like to use them with the exception of Marvel Mystery Oil so that's what I'll use. I add 4oz per gal. in my older vehicles, I'll just start including this one.

It seems like every time I change a fuel filter these days, there is ALWAYS some amount of water in the canister before the filter. Always. I hate this corn industry crap.

donbrew

Just curious, were is there ferrous material in the fuel system? The fuel rail looks to be aluminum alloy to me.

You will be surprised when you try to change the fuel filter on your HHR. It' not your father's filter, it is part of the fuel pump that can only be accessed by dropping the tank.