Help me troubleshoot this misfire - 2006 Chevy Aveo 1.6L

[NibbanaBanana]

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 should.

Any ideas?
Thanks.
Nibbana

 

[bullwinkle]

I would do a compression test to see if compression is down somewhat. How does the plug in the misfiring cylinder look? Any fouling at all of the new plug?

 

[Nick1994]

Agree with compression test.

Original fuel injectors at 263k miles?

 

[Hirev]

I would be suspicious of a spark plug. What plugs did you use? Do you or anyone you know have a scan tool for cars that does cylinder misfire counts? I would start there.

 

[dubber09]

How difficult is it to replace fuel filter on your car, if easy may be try that, esp if never changed?

 

[Jetronic]

decarbon the cylinders, I suspect you get glowing carbon in there under hard acceleration.

 

[GSCJR]

decarbon the cylinders, I suspect you get glowing carbon in there under hard acceleration.

This and make sure your EGR system is working, the carbon build up can plug the EGR passages.

 

[Oliveoil2]

If the plugs were changed and there was no mention of carbon fouling, then I’d be suspicious of paying for cylinder head cleaning. You probably got either a set of fake plugs (where did you purchase them?) or a bad plug wire if you used aftermarket.

 

[zrxkawboy]

You probably got either a set of fake plugs (where did you purchase them?)

^^^prime suspect

 

[NibbanaBanana]

Thanks for the responses. The car doesn't have a replaceable fuel filter. Just a sock on the fuel pump. I don't suspect a fuel problem because under any other load conditions it runs fine. Full throttle over 2000rpm is perfect.

As stated I used Denso wires so not the discount wires. I ran my spark tester and test light over them while it was running and they don't seem to be leaking voltage. At least not at idle.

I can't remember what plugs I put in but I think they are the same copper plugs that I've been running for the life of the car. Probably Champion, Motocraft or AC Delco. I just swap them every 30K and never had a problem. I will pull them and take a look. Unfortunately no sophisticated scan tool but I may have to get one.

 

[supton]

Unfortunately no sophisticated scan tool but I may have to get one.

I think you are stuck, time for a good one, to prevent chasing the wrong path. (I’ve been putting off getting one too.)

 

[D60]

Did OP state if he's getting misfire codes for a specific cylinder(s)? Or a P0300?

If new wires fixed it for one month why are we not at least ohm'ing wires or swapping (if possible) to see if the misfire follows?

If no hard codes look at pending codes

 

[NibbanaBanana]

Did OP state if he's getting misfire codes for a specific cylinder(s)? Or a P0300?

If new wires fixed it for one month why are we not at least ohm'ing wires or swapping (if possible) to see if the misfire follows?

If no hard codes look at pending codes

No codes.

 

[NibbanaBanana]

I think you are stuck, time for a good one, to prevent chasing the wrong path. (I’ve been putting off getting one too.)

What do you recommend?

 

[D60]

I'd take it out and try to make it misfire repeatedly and look for pending (and hard) codes. And can you get Mode 6 misfire counts on these? Even many ~$15 readers can do it -- often under Onboard Monitoring.

If you get a P0300 it's not much help but it would be nice if the ECM identifies specific cylinder(s) it doesn't like. Misfire counts will let YOU do this manually.

Older Ford trucks are notorious for a high threshold before even thinking about setting a code, but you can see misfires in the Counts.

 

[Trav]

Thanks for the responses. The car doesn't have a replaceable fuel filter. Just a sock on the fuel pump. I don't suspect a fuel problem because under any other load conditions it runs fine. Full throttle over 2000rpm is perfect.

As stated I used Denso wires so not the discount wires. I ran my spark tester and test light over them while it was running and they don't seem to be leaking voltage. At least not at idle.

I can't remember what plugs I put in but I think they are the same copper plugs that I've been running for the life of the car. Probably Champion, Motocraft or AC Delco. I just swap them every 30K and never had a problem. I will pull them and take a look. Unfortunately no sophisticated scan tool but I may have to get one.

That is usually (not the only possibility) a problem in the ignition system. This engine uses a waste spark ignition, double platinum or other double precious metal plugs eg NGK 2978 can really help in these systems. Check the wires, you would not be the first guy to get a bad part that failed shortly after install, check the resistance.

 

[supton]

What do you recommend?

Can't help you, I've been putting it off myself for years. I'd look in the tool section, maybe post a new thread (since every year something newer/better comes along). I'd make sure it supports multiple vehicles or can be flashed to add vehicles, since one never knows what the future brings (or you just accept that the scan tool might be only good for a few vehicles, and maybe not the next one--but probably costs less than one trip to a dealer & their diagnostic fee).

 

[zzyzzx]

I still want to know WHERE they bought the replacement plugs and plus wires.

 

[D60]

Even this VERY basic Launch cReader 319 will pull Mode 6 data. This is NOT a recommendation of this tool. I just keep it in my JL because it's tiny. Presently $28 on Amazon with a 20% coupon (for me, at least) but there's also a 3001 model for $18 that looks VERY similar.

I don't think these are built by Launch -- if you note the layout of the buttons a lot of low level readers are basically this rebadged.

Go to OnBoard Monitoring

Scroll to Misfire Data Cylinder X (four cylinders should only show 1-4, six cylinders should show 1-6 and so on)

and select each cylinder individually. Here on my '19 Wrangler Cyl 1 has a VALUE of zero, meaning zero misfires.

If your scanner reads "EWMA" that's just Exponentially Weighted Moving Average and you can disregard the acronym. It's just "VALUE" for all intents & purposes

 

[JTK]

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

As in pretty much flooring it from a stand still?

It would be neat to be able to trend fuel trims when it acts up. Unless you have lots of oil in the plug wells, it sounds like you have the ignition part of it (hopefully) out of the equation. Unless the engine twist/movement from the acceleration is causing an ignition wire to rub, an injector wire to rub and short, etc..

~260K is a lot for this segment of engine if she's all original.