2008 Chevrolet Aveo Misfire uphill (Chevy Again)

[Jetronic]

Cylinder-specific misfires are pretty easily determined by a combination of the consistency of the crank position sensor signal pulses and monitoring the resistance/voltage through the coils. Tiny variations of the speed of the crank through it's rotation make it easy for the ECU to determine whether any specific cylinder is firing or not. The ECU also monitors coil voltage, which relates to resistance across the spark gap. Low resistance, cylinder is firing. High resistance, not firing = misfire. Easy peasy.

that works for coil on plug, not so much for wasted spark, as the spark could be jumping through the wire insulation.

 

[robertfixit]

I see. I am used to older cars without the "misfire" calculation.

In the meantime, I put the camera on Cyl4 and it is also clean along with the #1. The cross hatching is beautiful, I wonder if the engine was rebuilt because it is unlikely with 120k miles for the head to be so clean. The water theory remains, but would it really leak coolant on all the cylinders? Usually not.

I was going to replace the injectors, but I am not yet confident that is the problem.

Pulled the intake pipe, TB had typical build up nothing abnormal and I cleaned it. The air filter was kind of dirty, but again typical.

After all of that, and monitoring O2 voltage, it is running rich quite a bit even in normal driving. I am starting to wonder if there is a vacuum leak somewhere. When the misfire happens it shows 100% load even though it is only part throttle.

In previous threads people have mentioned EGR valve issues. Considering the misfire happens at a specific load/RPM/throttle position, maybe there is leak there.

I am going to cap off the vacuum line to the EGR and see if that changes anything.

Otherwise, I'm stumped. I do not have a coolant pressure check tool. The car does not overheat. I have had cars with blown head gaskets before and usually you get a stumble at first start in the morning because coolant has seeped into the cylinder.

 

[robertfixit]

I bypassed the driver side vacuum lines to see if that might help. The vacuum line to the EGR was cracked. After finding the cracked hose I went AHA!

But, the issue remains...

 

[97prizm]

There was a thread about this here:

Thread 'Help me troubleshoot this misfire - 2006 Chevy Aveo 1.6L'

Jan 19, 2025

I still have a low speed misfire on my 2006 Chevy Aveo 1.6L with 263k miles on the clock. I changed to a new OE coil, new Denso wires and new plugs recently. The car was missing very bad about 9 months ago. I found carbon tracking on the high mileage plugs and changed them. Greatly improved but still a little missing now and then. I changed the wires which completely resolved the problem. About a month ago it started missing again. I now have a new OE coil and it's still missing.

The misfire only occurs under heavy acceleration below 2000 rpm. Other than that it runs and drive as it...

• NibbanaBanana
• Replies: 24
• Forum: Mechanical/Maintenance Forum

I was not sure whether to reply there or just start a new thread.

Anyway, my neighbors car is a 2008 Chevy Aveo5 1.6L with 120k on the clock. It has had a misfire off and on, but I was never able to really look at it because he drives it too much. But, in recent months, it has become worse. It seems to happen only uphill at low RPM, just like others have posted about. The code is misfire cylinder 2

I found the spark plugs 3 and 4 were covered in oil due to a valve cover gasket leak. I cleaned everything out and it was fine again, for a while. The problem returned eventually. I thought it was odd that it would say misfire on 2. I did not know at the time that 2 and 3 shared the same coil.

I pulled the plugs and boy they are worn out. You could drive a bus through the gap. The actual metal was worn along with the tip. I swapped 2 and 3 to see if that would make a difference. It was good again (for a while), and the problem returned. When it misfired, you could actually smell the oil burning. So finally, I fixed the valve cover gasket leak and now there is no more oil pouring into the spark plug area.

With all of that done, the problem remains. I thought *maybe* the constant oil on the plug wires had caused them to fail, so I put new wires, same issue. At this point, I pulled all of the plugs for inspection and found #3 to be cracked in the ceramic (a big one), which was originally on #2, but the code is still for #2.

I ordered new plugs and a coil pack. It needs new plugs anyway and I see that many people have had coil issues. Here is the odd part. I moved the cracked plug to #4, #2 to #1 and went for a test drive. Still #2 is the misfire.

So my question is, can half of the coil go bad? I assumed that a twin fire coil was sort of one piece. I have never seen part of it fail, unless there is some internal crack or something that would cause half of it to not work properly.

As another test while we wait for parts, I switched the #2 and #3 wire. I did not realize it is a wasted spark system and we could do that. Went for a test drive, works fine until the hill, then misfire. What I was hoping for was a #3 misfire, but no codes popped up.

I hope the coil is bad and that solves the problem. I just wanted some input or theories for reference that other people might look up.


Note: I went for iridium plugs. But from what people have said here they prefer copper or platinum for longevity.

I'm oddly enough having a Similar issue with my 1997 Chevy Cavalier.