07 GT500 coil packs with 105k miles: Test? Replace? Leave 'em?

@shelbygirl - can you be more descriptive of "not accelerating well"

RhinoRacing said:

I would not put the old plugs back in. If anything re-gap the new plugs to 35-38. Make sure the coil packs are fully seated on the spark plug. If they are not they can still fire the plug so the car will run but not efficiently. I would start here and then go from there.

FYI I run a gap of 28 on my GT500 with a 2.9 Whipple and 28 in my Cobra Jet. But I run NGK plugs in both the CJ’s get changed every 10 passes as it runs on 116 octane fuel.

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jewc75 said:

Gap at .028 or .032, most tuners will tell you to do that and most prefer the TR6 plugs as Gabe suggested earlier.

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in general you want to run a bigger gap - in OPs case from what I see in the thread the car is stock, no need to run a gap that small IMO, I run 21# of boost with a .028 gap on a TR6 copper plug, the reason to gap down is to avoid blowout of the spark due to pressures, IMO stock gap at .044 is appropriate in the OP's case

RED09GT said:

0.044" is stock but is on the high side for a boosted motor.
If you are running it hard or taking it to the track, or adding more boost, I'd try 0.035" but if you are just wringing it out on the street from time to time and are at stock boost levels, 0.044" is just fine.

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So what exactly is the factory boost levels for the 2007-09 GT500? If it's between 6-7.5 lbs boost? Then I don't quite understand how 0.044 is the recommended gap specs. I also agree 0.044 is most definitely on the high side for a boosted motor, despite being a stock "07-09" GT500. Needless to say, the recommended gap specs for my "06" GT with Saleen VI blower and 3.6" pulley is between 0.030-0.032 lol.

~8# is stock boost

stkjock said:

~8# is stock boost

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Then I'm definitely at a loss as to how a 8lb boosted 2007-09 GT500 has a factory spark plug gap spec of 0.044 which IMHO is also quite high for a F/I application and is also around the same gap specs for the N/A 4.6L 3 valves

I re-gapped the new motorcraft plugs, from .044" - down to .036" and it runs quite a bit better. The initial throttle response is still sluggish, but quickly picks up over 2200 rpms. Then it feels strong. I may try .033", but for now, it is what it is.

If you have not already done so: clean the maf, throttle body, air filter and replace your fuel filter.

Initial throttle response is mostly dictated by the stock tune and the drive-by-wire system. An aftermarket tune is the way to go and since you are well out of warranty, nothing to lose by going with a better tune.

Are you saying that it has recently changed for the worse or it just isn't meeting expectations? If it is the latter, get a tuner and an email tune from someone like VMP and your initial throttle response will no longer be sluggish. If it is the former, try having the fuel injectors cleaned as well-looking at your plugs, that car has seen some suspect fuel somewhere along the way.