TrevorS

iTrader: (1)

Aprox 9500mi and my VIN is after the engine harness TBS serial break.

Was just pulling out of a stop when the engine stumbled, seemed reluctant to rev, and the Xmas tree lights turned on . I proceeded gently and it seemed to recover, but I took it easy to my destination. Didn't feel right for another intake system glitch (which would probably be traceable to me ), but on the trip home, it behaved perfectly normally. Got home, hooked up my new scanner, and it reported a P0353,which is a coilpack C problem -- I take that to be cylinder #3. I reviewed the freeze frame data and nothing I recognized seemed strange -- not that I'm experienced with the jargon .

So, I cleared the CEL and all I can do now is see how soon it recurs. If it does, I guess I'll try swapping with number 2. But really, that doesn't seem all that many miles for this problem to be showing up -- wonder what the failure rate relationship is with engine compartment temp (a header raises the temp compared to the OE shielded manifold)?

TrevorS

iTrader: (1)

Thought I should mention a couple things. The header has only been installed for 1300 miles (downpipes roughly align with cylinder #3), and when I first tried out the scanner the day before the CEL, it reported there had been exactly one misfire, also cylinder #3. I should have checked for misfires again before clearing the CEL, but didn't think of it and then it was too late. Think I'll check that periodically.

Am thinking it may make sense to remove and reinstall that coil pack in case it's just a contact quality issue. I'll wait for the next sign of trouble though -- was completely normal today.

ScionFred

iTrader: (1)

I highly doubt that slightly elevated engine compartment temps have anything to do with this. Given the prevalence of early XB2 coil failures, the TSB for the same and service reps telling customers that the coil packs have been improved (design, material or construction flaw fixed), I would wager that you have a #3 coil pack going bad.

Try moving coil #3 to another cylinder and see if the misfire and/or coil failure CEL moves with it.

Another possible solution for those out of warranty and looking to extend their coil life is to re-gap your spark plugs or change them to .032 gapped plugs. I had to do this when I installed my turbo and haven't noticed or have any reason to expect any significant degradation in idle quality, performance or fuel economy. If by chance you extend your coil life by 20k miles at the expense of 1 mpg, you'll save more than the cost of one replacement coil per 20k miles.

My 07 coils are still fine after 48k, knock on .032 gapped NGK iridiums...

NocturnalxRS6

A forced induction vehicle generally requires a closer gap than n/a. I wouldnt recommend .032 at all unless youre boosted.

ScionFred

iTrader: (1)

I see your point and agree in principle but my engine spends the vast majority of time out of boost yet still runs like stock. The smaller spark gap hasn't caused any noticeable effects out of boost. I imagine there could be a slight increase in unburnt fuel and loss of fuel economy but I haven't noticed any. Much like running 5w30 oil instead of 0w20 has theoretically cost mpg but not enough that I can actually measure it.

TrevorS

iTrader: (1)

Just checked the misfire monitor and there's been no recurrence. I plan to hold off moving anything until a pattern develops. I think my first step if it does start recurring will just be a remove and re-install. If it continues, then a swap with number two.

NocturnalxRS6

I just noticed your mod list, I wonder if a good dyno tune will help your problems if you havn't done so already not mention a very noticable performance increase. And if it doesn't work youll still get something out of it

TrevorS

iTrader: (1)

Perhaps that's true, but I'm very much aware that air flow through the radiator no longer takes heat away from my lower pipes and the heat shields that used to help keep the heat directed down from the engine cover area are no longer present. Combined with the hotter running single pipes coming from the head (due to the pipes below them being insulated) the changes do result in higher temp air flowing under the cover and around the packs. How much higher? I don't know, but it's pretty apparent when I open the hood immediately after shutting off the engine. I'm thinking the short interval between the header mods and the CEL to be suspicious, and 9.5K on the clock just seems a little early.

Seems to me that without installing a piggyback, there's nothing to tune ! Also, not clear how that would assist with a coil-pack CEL (no other non-dumb problems experienced so far).

Thinking of a piggyback, I was looking at the Unichip and contacted Unichip.com with a simplified version of my mod list, expressing serious interest in their product, and requesting their input on whether they had anything in the can that might be suitable or whether it would require a tuner. After almost a week went by without reply, I tried again. It's been six days since that second try and it's appearing clear they've no interest in talking to me. Maybe it's because I mentioned I intend to continue using 87 octane???

I also looked for the nearest Unichip tuner, and he's about two hours away with a minimum cost (according to his published rates) of around $350. All in all, not a very encouraging scenario !

ScionFred

iTrader: (1)

Well, it seems to me that we don't know whether insulating your header collector and s-pipe have caused more thermal energy to be radiated through the un-insulated head pipes than the reduction the insulation provided. We do know that some thermal energy, previously radiated underhood, is being re-directed through the exhaust system aft of the engine bay now.

We also don't know the effect of removing the exhaust heat shields. Hot air rises and AFAIK wouldn't be deflected downward out of the engine bay by those exhaust heat shields in the first place. My understanding is that the increased surface area provided by the heat shields would increase thermal radiation to the surrounding air while reducing the surface temp of the exhaust system and shields. Let's just say that I am not as convinced that your underhood temps are any higher than before. Frankly, despite my cast iron exhaust manifold and turbo, I haven't noticed any change in underhood temp. It was hot stock and it's hot now. But then I must confess that I can't tell 170F air from 180F air just by how it feels on my skin.

If you think that heat may be causing your coil problems, why not remove the engine cover? That sound-deadening insulation under it looks like pretty effective thermal insulation to me. Surely removing it would reduce the temp of your coils.

TrevorS

iTrader: (1)

FWIW -- after wrapping the lower portion of the header, there was a definite impact on the color of the single upper pipes (less black and more brownish), took it a good week for the color to restabilize. Plus there was an apparent temperature increase under the hood with very apparent metal contraction after shut off, distinct and pronounced "pinging" that I hadn't previously heard. Let's face it, if the lower pipes are held at a hotter temp, then the upper pipes are going to be hotter as well, nature of the game. In my view, I have a heat column rising amidst the four down pipes and splashing in the vicinity of the third coil pack. Whether or not that "should" cause a problem I've no way of knowing, but it at least seems as though something may be going on !

The OE heat shields provide a reflective surface that although they radiate upwards, also definitely deflect downwards. That deflection is completely removed absent the shields. Also, at least to me, the temp difference under the hood between OE and my current is more than striking. What effect that would have on the coil-packs, if any, I've no way of knowing. However, my experience with electronics in general is heat can be a major aggravating factor !

Please understand, I'm not saying this interpretation is necessarily correct, but I can't help but think it's a real possibility.

ScionFred

iTrader: (1)

I don't know Trevor. All I do know is that ordinary people like me need dynos, drag strips and thermometers to assess hp, tq and temp as accurately as you seem to be able to do simply by postulating a theoretical outcome and then confirming it subjectively.

I haven't made it to Harbor Freight yet but when I do buy that infrared thermometer, I'll be happy to loan it to you so you can take some actual measurements. Personally I've seen too many times that my sensory perception of things isn't always confirmed by more scientific methods. Especially when I have preconceived ideas of what to expect beforehand.

No offense meant although I can understand if some is taken and hopefully forgiven.

TrevorS

iTrader: (1)

No problem man, I'm experiencing what I'm experiencing with my xB2 and mods and the outcome will be the outcome! Just got to see if a pattern develops on cylinder #3. I've ordered materials for wrapping the single pipes, but it's not my first choice -- kinda like it the way ir is ! (FWIW -- theory counts for a lot to me, blame my academic background !)

ScionFred

iTrader: (1)

Cool. IMO you're on the right track by wrapping the header pipes. If you want to further reduce your coil temps, removing the thermal/sound insulating engine cover should reduce them significantly more. The heat radiating off the valve cover is certainly hotter than the surrounding air.

TrevorS

iTrader: (1)

Well, well! Just having one of the warmest days around here for awhile and while stopped awaiting a light change (just like last time) I once again got a CEL on coil-pack three and the engine began stumbling. The misbehavior cleared shortly before the light changed, but I did feel another stumble while gathering speed. Seems pretty clear heat's the trigger for the problem (while cooler outside or the vehicle is moving, the engine compartment temp is lower and the failure doesn't occur). Don't know if it's specific to that particular coil-pack or that above-the-vertical-pipes location, but I do know the problem never occurred before wrapping the header verticals leaving the upper singles unwrapped. Looks like it's time to install the upper header wrap and see if it reoccurs.

I copied down the pertinent OBDII freeze frame data so if it happens again, I can look for any interesting differences -- though given it occurs during idle, I doubt the readings would change much.

TrevorS

iTrader: (1)

Goes in Sunday, here's hoping the CEL doesn't repeat.

TrevorS

iTrader: (1)

Took a lunch run with the fully wrapped header and on getting back immediately popped the hood to check engine compartment temp -- way cooler! Guess I could always be surprised, but I'm expecting that CEL to be history !

ScionFred

iTrader: (1)

The CEL will be back, just give it time.

On a more positive note, the newly wrapped header looks great and should perform better than the previous partial wrap.

TrevorS

iTrader: (1)

You're a hard task master Fred ! Still, no question I'll be disappointed if it occurs again, however, if it does, next step will be to swap the #1 with the #3 coil pack and again cross my fingers ! Should there be another failure, it may well not be until neighborhood June of 2012.

ScionFred

iTrader: (1)

Sorry Trevor but I call 'em as I see 'em and even a "way cooler" reduction in subjectively perceived underhood air temp after performing a mod subjectively expected to make a big improvement is not likely to revive a failing coil pack, IMO. I could be wrong of course and I do hope that this extra header wrap somehow helps but I doubt it will.

TrevorS

iTrader: (1)

Well, that repeat CEL only took 210mi, so if I've misinterpreted the scenario, it shouldn't take too long for another to show up -- if that happens, I'll report it!