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Engine shuddering and surging - Details inside


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I forgot to look at these yesterday. I'll try to pull them up on the work computer later.

 

I believe all af corrections are from the forward o2 sensor in the up pipe and the maf sensor. Since you don't have a splash shield, you could either have a weird grounding issue or more likely a shorted or exposed wire at one of those points. Is it the stock air box set up?

 

Also in the car wash it should only mess with the first a/f value as you'd be idling I believe.

 

 

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The engine is completely stock with the exception of AP flash and air pump delete.

 

I'm with you on that front O2 sensor which is why I have been questioning it. Seems that I'll be going for a pair of OCV's and an upstream O2 sensor on my next parts purchase.

 

FWIW, AF Correction shows mostly zero when idling when the car is dry. This can be seen in the 3rd log.

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I'm interested in this as well because I have the random 800-300-1000-800~ RPM shudder on idle. It's not all the time either. Providing ANY gas what so ever 'fixes' it and get it back to normal. I have another shudder around 2300 RPMs, but supposedly that's the fuel pump.
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  • 2 weeks later...

Front O2 was installed last Friday and I noticed damaged insulation on all of the wires for the old O2 sensor. It appeared the wiring was also damaged due to corrosion.

 

After a few hundred miles of driving, the part-throttle highway surging has pretty much gone away completely. Keep in mind I am nitpicking this detail as I believe the OCV's are also at play here.

 

There is, however, the ever so slight shudder effect still happening during small throttle inputs at low speeds. This effect has also been reduced greatly but not eliminated. Again, an improvement with the replacement of the front O2 sensor.

 

The wet conditions are no longer a factor, likely due to the broken insulation and damaged wires on the old O2 sensor.

 

So, in my opinion, a huge step in the right direction just by replacing the front O2 sensor. The engine certainly runs a lot better.

 

Unfortunately I did not capture the before and after values of the O2 sensor readings otherwise I would have put those up for comparison.

 

OCV's are next...

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  • 11 months later...

So I finally picked up a pair of factory OCV's and those will be installed soon, hopefully this weekend.

 

I am wondering, though, can OCV's be bad enough to throw an engine misfire code? I've seen 3 CEL's in the last week...2 of them were for Cyl 4 misfire and the other was Cyl 1 and 4 misfire.

 

Doesn't do it in Intelligent mode but it has happened while in Sport Sharp mode all 3 times. Haven't checked in Sport mode but I doubt that really matters.

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Usually, if they throw a code, it's pertaining to a timing issue. Mine failed without a CEL, so YMMV.

 

In Intelligent mode, isn't that akin to an "economy" mode? Meaning the turbo is in low boost? If so, you might just have a simple vacuum leak. Higher boost pressures will expose more vacuum leaks.

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I'll check the vac lines when replacing the OCV's. The reason I asked about the relationship between the CEL and OCV was because of the CEL for Cyl 1 and 4 misfires.

 

Any thoughts on a coil or two failing? They were new when the engine was installed (~30,000 miles ago) however, they aren't the factory coils.

 

Also, I failed to mention that the CEL's showed up during WOT only. I do have a logs each for Intelligent and Sport# modes respectively.

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Stock intelligent mode limits boost to 8psi I believe.

 

Unlikely a coil failed after only 30k, especially two I would think. But just swap them with two and three. Easy enough to test.

 

Can't help beyond that.

 

 

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You can swap coils as Nonamedude said to see if the misfire code follows those cylinders. I never screw around with aftermarket ignition/spark/timing components ever. Always go with tried and tested OEM for those.

 

Good luck getting those out though. They're a pain. Recommended to do it from underneath.

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You can swap coils as Nonamedude said to see if the misfire code follows those cylinders. I never screw around with aftermarket ignition/spark/timing components ever. Always go with tried and tested OEM for those.

 

Good luck getting those out though. They're a pain. Recommended to do it from underneath.

 

 

I was lucky enough to have the engine out. Just went ahead and bought all new ones. Pretty sure I went with whatever the oe brand is instead of buying from the dealer though.

 

I've heard easy mode spark plugs is to unbolt dog bone and jack up the front of the block.

 

 

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Yeah, I hadn't realized my mistake with using aftermarket coils until it was too late.

 

As it turns out, I won't be changing anything this weekend as it's very cold and we have a bunch of snow on the way...

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  • 2 months later...

Update:

 

The misfire was solved and definitely not related to the OCV's. The misfire ended up being a bad coil.

 

As far as the OCV's are concerned, I installed a brand new pair earlier today. The surging and shuddering has been completely eliminated!

 

:):):)

 

:cool:

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