Asking the Mechanics for Help with 2008 Chevy HHR

[DDTSGM]

Yes, I drive a chic mobile when I'm not in my truck. Much better mileage.

Anyways, the HHR has a fresh factory re-manufactured engine in it (long story). Shortly after I got it back the check engine light came on while I was driving in town, several moments later when I looked, it had reset, then it came back. It was a weekend so I ran to Auto-Zone and read the code - it showed an intermittent misfire in #1 and suggested new plugs or a coil pack. Since the plugs were fresh, I figured coil pack and decide what the heck, replace them all. It reset for a bit them came back on, so I checked it again, same code.

At this point I pulled the plugs and #1 looked a little oily to me. So, I took it back to the chop that had replaced the engine. They check compression, plugs, injectors, etc, did a factory reset and the mechanic drove it around with their scanner hooked up. No problem. They also told me that they had placed #1 plug in #2 hole so that if it threw the code again and it was #2 they'd know it was the plug.

Today, 47 miles after the service it threw the same code. I forgot to add that at several points the check engine light started flashing and it was running rough while stopped at a light, returned to non-flashing as I pulled away from the light, which indicated to me that a cylinder wasn't firing.

At this point, I'm paying for whack-a-part. What would be the next step?

[fixer]

What did they do to check injectors?

Did the plugs get replaced?

I've seen new plugs be defective with the ceramic/porcelain cracked and it wasn't noticed during installation. after a few miles driving the carbon tracking was pretty obvious. And the misfire was random.

I would try a new set of plugs with the right heat range and factory part number then go from there.

Basically...

if data is not showing major corrections on fuel trim, but a misfire is still being flagged, and you are getting symptoms of a misfire on only one single cylinder, then there might be a deeper mechanical issue.

Compression tests are good to get a quick understanding of any major issues. A leak down test can indicate a more certain test of "compression integrity".

Was the cylinder head replaced with the engine?

[farscott]

If there is oil on a spark plug, a gasket or seal is a culprit. I would check the valve cover gasket as that is a known issue with the HHR engines.

[AKDoug]

If there is oil on a spark plug, a gasket or seal is a culprit. I would check the valve cover gasket as that is a known issue with the HHR engines.

I don't know anything about HHR engines, but lots about other engines. Why would a valve cover gasket be a culprit on an internal engine issue? Head gasket I could see.

Misfiring is going to be ignition, fuel delivery, compression or contamination. You've already ruled out ignition. Injector function needs to be checked, compression and leak down need to be checked, and head gasket needs to be checked.

[Erik]

As far as I can tell from the OP, ignition hasn't been ruled out - just a bad plug. Could still be the coil pack or wires. Could also be something internal to the PCM, which can be much harder to diagnose or the wiring harness. Let the shop follow up on the diagnosis unless you don't trust them. They should be able to test the coil pack and pull the plug again to see if it's oily. A random intermittent issue like that doesn't sound like a gasket; more like a loose connector, bad sensor, bad ignition component or wiring. From a die hard GM guy: GM electronics suck.

[0ddl0t]

Oily plugs concern me, especially on a brand new engine. Is the plug fouled again now?

What caused the original engine failure?

[JRB]

If it's still the same #1 code and the coil pack and plug have been replaced, and the code is coming back that quickly, as fixer already stated it's time to move an injector to another cyl like they did with the plug and coilpack on #2. An injector is the best case scenario here.

Start with a leakdown test on all four cyls and see if #1 is low. Compression tests can find big problems but on a poorly rebuilt engine I've seen decent compression but poor leakdown if something got screwed up with the ring gaps or cyl hone or whatever. At which point it's time to start a warranty claim on that reman motor. Oily plugs have me leaning this way, unfortunately.


If the leakdown and compression are both good and the injector swap doesn't move the problem, try an intake leak test/smoke test/etc to see if there's a small intake manifold leak in the runner to cyl #1. Typically that would throw CEL's for other things too like MAFS values read by the PCM being out of wack, but with the short duration of your PCM resets they might not have had time to 'fail' enough to throw their own CEL. I don't expect this to be the case, but it's a possibility that's easier than replacing the whole engine.

Easiest way to do DIY that test is get some flammable brake cleaner and spray a short squirt the gasket seams of each runner as the engine is idling. If the idle goes up briefly when you hit a spot, you know there's a leak at that spot. Only downside is on inline engines you it's usually a PITA to get to the underside of the intake manifold to accurately hit the underside of each runner, but getting to the top of each runner tends to get the injector seals as well as 70%-80% of the whole runner by proximity. It's just not a perfect

I don't know anything about HHR engines, but lots about other engines. Why would a valve cover gasket be a culprit on an internal engine issue? Head gasket I could see.

Misfiring is going to be ignition, fuel delivery, compression or contamination. You've already ruled out ignition. Injector function needs to be checked, compression and leak down need to be checked, and head gasket needs to be checked.

Oil that leaks into the spark plug valley on a DOHC engine can get in between the plug and plug wire or coil pack. The added resistance is sometimes enough to cause a misfire or spark blowout under load on turbocharged engines.

[DDTSGM]

Thanks to all.

Yes, the head was replaced, it was not a short block. That being said, the ignition components are all 12 years old and have been removed and replaced couple times.

Yes, I trust the shop, I tend to keep vehicles a long time and they have done some major work for me with no complaints, and, it's a long story, but they treated me very good on the engine replacement deal.

ETA: They checked the injectors, did compression, don't know about leak-down as I didn't keep the receipt (dumbass).

Right now I'm focusing on ignition as the source. I'm fairly comfortable with non-electronic, cam-in-block, carburetor engines; over my lifetime I've rebuilt and or replaced several. I'm definitely out of my depth with this ignition system.

At this point I was thinking my next step might be to replace the ECM-PCM, but that is getting a little to pricey to be playing process of elimination.

Don't know if it is related, but right before this happened, my automatic power door locks stopped working, I replaced the fuse, worked for awhile then it popped again.

[DDTSGM]

Oily plugs concern me, especially on a brand new engine. Is the plug fouled again now?

What caused the original engine failure?

Timing chain slipped.

[AKDoug]

Oil that leaks into the spark plug valley on a DOHC engine can get in between the plug and plug wire or coil pack. The added resistance is sometimes enough to cause a misfire or spark blowout under load on turbocharged engines.

Copy that, as I said I'm not familiar with that engine. You would think, though, that they would have caught that if changing the plugs.