I get how difficult it is to diagnose like this but I'm looking for ideas:

2009
125k

The issue looks to most people like faulty spark plugs or plugs that need to be replaced. So I did that and it didn't fix the issue. The symptoms:

Sometimes it runs ok but other times it feels rough how the car drives, you give it gas but it stutters. It's more noticeable in 3rd gear and 4th.

Occasionally it gets bad, the engine light turns on and basically it stutters a lot and it feels like the engine is not getting the gas at all. At that point I don't drive it. Occasionally, once it reaches that point, if the car sits long enough, when you get back to it, it's fine for a time.

 

CEL is always misfires.
Coils are the usual culprit, which in turn causes cats to clog up, which can also cause misfires.
Get your OBD scanned for trouble codes.

 

Makes sense.

Thanks for replying, I'll post the results of all this. Since coils seem the practical solution those run about a $100 for stock or close to that?

 

Around $35 each from Advanced Auto with an internet discount.

 

with 125 K miles on this 2009, I would start by checking fuel pressure. low or intermittent variance in fuel pressure will cause these symptoms.

I would start by measuring fuel pressure. If below threshold then I would replace the fuel pump relay, since the contacts inside deteriorate after XXXX cycles causing higher amperage draw and slower fuel pump pressure. If no improvement then it is the pump.

If fuel pressure is normal than I would go down the ignition path of coils wires plugs etc.

 

I see. Thanks for that information. I had him look at the coils and the leading coil was totally out, so that got replaced. At the moment it looks as if that is the issue. Or was. Until I get stranded on my way to work again....

Those fuel pump issues, are they big costly ones? I'm guessing they're not the problem but you know a lot more than I do.

 

Lately I have been seeing this misfire problem due to low fuel pressure / intermittent low pressure caused by relays and fuel pumps, with German & Japanese cars w/ over 100 K miles.

Glad to hear that your problem was due to a coil pack.

 

So it was the leading coil, like he said. I've been running smooth for a few days. Thanks guys, learned a few things.

 

Glad you found a solution to your issue. I had similar issues on my 2005. Was getting intermittent misfires even with new plugs. I swapped the coils and that did the trick.

I would HIGHLY recommend a bluetooth OBD II Scanner paired with an app like Torque Pro. Not only will it help you read error codes, but you can see real time information like engine load, MAF readings, and mpg. Very handy and not expensive.

 

I don't believe faulty fuel pumps trigger CELs.
Mine failed suddenly with no warning at around 40k.
Engine shut off repeatedly for about 30 miles, but luckily I was able to nurse it home.