(Resolved:) Rough Idle, no codes

Reprise

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Jul 22, 2015
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Putting this in as a placeholder; I'm not broken down, but starting the truck up after stopping for lunch, it started idling very rough. Power seemed to be ok while driving to my next errand.

Hooked up Torque pro, and everything seems ok. I captured a couple of logs, etc, and will review when I get home.

As for recent changes, I put 1oz / 30ml of tracer dye in the crankcase today, on the drive cycle before it started idling rough - but I know that's not the issue. No noises to indicate a lubrication problem.
As for maintenance, she got a set of the proper AC Iridiums a few weeks back - the old ones looked fine - only issue was that they were Bosch. And she has a fresh oil change.

Started again as I write this, turns right over. Will see what the ride home is like. Started idling like crap again in the time it took to thumb these 2 sentences out on my phone. Maybe a little bit better? Perhaps bad gas - it has a new inline filter, though. Fuel pressure is reported as about 32 psi by torque -?

On edit - 1 min after I sent this post, my SES light came on. Misfire cyl 3. At least I know where to start looking. I suppose it has to repeat for a minimum # of cycles b/f it throws the code.

More later; I know first things to check / swap are plug wire & coil.
 
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Reprise

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@MRRSM - thank you for that link - very helpful.

From what I see, the odds are that the coil will need replacing; I'll be working on this later this afternoon.

Guessing that AC Delco is the way to go here, as with most things electrical (?) - but it looks like I may have trouble sourcing it locally. If anyone can recommend a non-Delco brand, feel free to post. My concern is around availability, not cost. Thx.
 

Mooseman

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Dec 4, 2011
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Ottawa, ON
Just looking at RockAuto, there are two possible types; round or square. If yours are round, Delphi is/was OE. Easy way to tell is that the round one has an aluminum heatsink on top.
 

Reprise

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Sorry... I should've been more clear - 'availability' meaning 'today via retail' vs. ordering online, as I didn't want to have the truck down for the weekend. :duh: BTW, I have the round ones w/ heatsinks - apparently, those were prevalent on the Gen-III engines (?)

I do have some good news, however - it appears my issue was a loose plug wire. I noticed when I pulled off the top / coil end of the wire that there seemed to be excess movement on the plug end. Replaced the wire, reset the misfire code, and she's all clear over 3 restarts and 20min or so of idling in the garage.

I'll drive her around a little later to ensure all is well.

One last question for the forum...
Regarding coils...I know people have had to replace them on occasion. When one goes, are others 'not far behind' ? Reason I ask is because I'm seeing sets of 8 (Delphi, others) for about half the price of what it would cost to replace 8 individually. The ones that are on there now all appear to be factory OEM (and the truck has just over 141K on it). Appreciate any / all replies.
 

Mooseman

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Dec 4, 2011
25,260
Ottawa, ON
Not necessarily. On the I6, one that often fails is #4 because the water drips off the cowl lip right onto it. On V8's, I don't see that as an issue. Maybe it was subjected to more heat or some other factor killed it. Probably just a fluke.
 
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