p0300 missfire on highway

[cooldude919]

This only seems to happen when im on the highway in 5th gear. Car will sputter / run really rough and the wideband goes very lean, then if i just push in the clutch and let the rpms drop im good to go for a bit again. Sometimes it does this every 10-15min, sometimes less sometimes more. Car runs fine around the city, only happens when crusing on the highway.

http://www.dsmtuners.com/forums/problem-diagnosis/241406-my-p0300-fix.html

seems similar to this thread. Could it be the alternator?

Im running the cheap xtd flywheel and clutch, i thought i remember someone saying a lighter flywheel could cause these problems?

My profile is pretty much updated, but let me know if you need anymore information.

 

[PieEyedPiper]

Welcome to the club.
My only solution has been to use Pennzoil Platinum Synthetic 10w30. You know, the stuff with the gimmicky "molecules that break apart and recombine" schpeal. It seems to be the only thing that has had significant impact for me. Only one CEL/P0300 code in the last 6 months, literally, compared to dozens a month sometimes with Mobil 1.
I'm convinced something else entirely is at work, but so long as I've got this cursed plague of doom at bay, I'm not gonna f' with it.

 

[Twistaye]

Well, looks like a logical place to start, I'd probably go ahead and change the alternator, even though it's not cheap, it might be the best bet you have so far. Your symptoms sound like his, and if the voltage problems were affecting him so much, then maybe it'll help you? Although he said he would get his cels from just driving to the store, and you only have problems on the highway. They can test your alternator at Autozone, maybe that's one thing you could do? Hope you get it figured out

 

[cooldude919]

Welcome to the club.
My only solution has been to use Pennzoil Platinum Synthetic 10w30. You know, the stuff with the gimmicky "molecules that break apart and recombine" schpeal. It seems to be the only thing that has had significant impact for me. Only one CEL/P0300 code in the last 6 months, literally, compared to dozens a month sometimes with Mobil 1.
I'm convinced something else entirely is at work, but so long as I've got this cursed plague of doom at bay, I'm not gonna f' with it.

Interesting. I do use mobile one normally. I suppose this is worth a try to see what happens.

 

[cooldude919]

Well, looks like a logical place to start, I'd probably go ahead and change the alternator, even though it's not cheap, it might be the best bet you have so far. Your symptoms sound like his, and if the voltage problems were affecting him so much, then maybe it'll help you? Although he said he would get his cels from just driving to the store, and you only have problems on the highway. They can test your alternator at Autozone, maybe that's one thing you could do? Hope you get it figured out

Wheres the best place to get a good alternator? I hear bad things about the reman ones, so where should i look, ebay? I have autozone, advance, and oreillys near me.