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View Full Version : Stock spark plugs.....


cobra2112
06-19-2006, 08:17 PM
I am in the process of returning my 04 back too stock. (pulley, tune, etc.) What are the stock spark plugs and gap for my car. My manual lists AGSF-22FMI with no gap info. I have the NGK TR6's in there now.

mrpork
06-19-2006, 08:32 PM
why would you want to go back

cobra2112
06-19-2006, 08:42 PM
Too many quirks with the tune and pulley. I don't take it to the track or drag at all. She is still plenty quick. Just takes a little more go pedal now.:thumbsup:

FactoryFreak197
06-20-2006, 12:40 AM
[QUOTE=cobra2112]Too many quirks with the tune and pulley. I don't take it to the track or drag ha

Ive had mine over a year with pulley, and similiar mods, I never have had a problem, driving it on the hwy and out of town.

ausie
06-20-2006, 06:26 AM
Too many quirks with the tune and pulley. I don't take it to the track or drag at all. She is still plenty quick. Just takes a little more go pedal now.:thumbsup:
If you really want to return to stock plugs, the gap info is listed on the emissions sticker under the hood. Stock spark gap 0.042 ~ 0.046.

Depending on what boost level you have, the stock plug may not be the best choice. Also, the coil packs will not perform their job if using too cold of a plug. It could be a matter of the spark gap (too much of a gap could cause issues in the high RPM range unless you have a spark booster, and too short of a gap will cause a weak spark voltage. Irridium plugs work best at around 0.034 to 0.040. If the plugs have been in for a while, it would not hurt to remove them an inspect the plugs and recheck the gap. Unfortunately they do not last forever since the electrodes and or ground prong will erode from the arc. However, if you noticed a change in performance over time, it may just be a matter of cleaning the MAF (requires a different cleaner than the other parts), throttle plate, etc... and if you still have the Eaton, I found that removing the inlet tube (from the throttle all the way to the supercharger) was a great way to access the boost bypass valve to clean that as well (not something to need to do but once in a great while). If you do intend to use throttle body cleaner (aka: air intake cleaner) best to do so before an oil change so that any of the solvents that may find their way into the crank case can be removed when you change the oil. Use caution as the cleaners will remove paint if it drips onto the valve cover as well as damage the coating on the supercharger rotors if you attempt to spray it into the supercharger and allow it to pool or sit too long. It is difficult to use the intake cleaners while the motor is running and is probably not necessary unless you have consumed an excess amount of oil through the intake (PCV or breather line) to clean the intercooler since that can get gummed up too. I have been thinking about using seafoam but still unsure of how it would affect the supercharger or other components. In most cases, cleaning the parts mentioned will help sluggishness. What would be great would be to discover a chemical that could be used to clean spark plugs that would not react with the metals or etch the ceramic insulator.

cobra2112
06-20-2006, 11:55 PM
Does anybody know what plugs came stock with the 04 Cobra?

Cobra G
06-21-2006, 02:33 AM
I'd go with what ausie said
Does anybody know what plugs came stock with the 04 Cobra? If you really want to return to stock plugs, the gap info is listed on the emissions sticker under the hood. Stock spark gap 0.042 ~ 0.046.

ausie
06-21-2006, 07:29 AM
Does anybody know what plugs came stock with the 04 Cobra?
yep. :cool: I kept mine when I replaced them with Denso IT22's. The 04 Plugs are the same as what you have AGSF 22FM1. Only ran them for less than one year before swapping them out for Denso's gapped at 0.034".

If you are trying to cure any issues that you now have with the pulley and tune, changing the plugs may be a logical choice at first but it may all be a matter of A/F ratios. From start to about 2800 rpm the stock tune will run on the lean side at about 14.7:1 and will flatten out to a nominal 12:1 range until it gets closer to 5000 rpm where it goes rich to 9:1 to prevent burning out the cats. There was a very interesting article on the mustang 5.0 website that was doing a comparitive report on exhaust cat back systems along with hand held tuners (Preditor and SCT) which also included a pully swap. The predator tune followed the ford spec as far as the fuel ratio is concerned but may have changed the timming. As for the SCT, it basically stayed a consistant 12:1 ratio without any regard to enrich the fuel ratio at the top end. If for any reason the car seems sluggish or has lost its edge, I would check the MAF sensor for contamination since it is extremely sensitive. Also if you are pushing the Eaton farther than the nominal 8-10 psi of boost you should be using a colder plug than stock. You may also need to use a spark enhancer ignition device to compensate for colder plugs since they tend to slow the transient pulse of the coils. Probably best to diagnose any issues with a wideband A/F meter while on a dyno to see what exactly is happening.

cobra2112
06-22-2006, 11:48 PM
Thanks I will try the Denso IT22's.

ausie
06-23-2006, 07:31 AM
Ford change the heat range on the spark plugs from 03 to 04 by one heat range (I am assuming this by the application guide in the denso web site). Not quite sure if the coils have the same part number. Some that have used the plug have had issues with the insulator cracking either due to more boost since they are running a whipple or KB, or even a ported Eaton. You need to match the plug to the amount of boost or you will have issues. Read this....

http://www.ngk.com/charglossary.asp?kw=Heat+range

I was looking at the NGK web site. The NGK TR6Ix looks almost identical to the Denso plug (does not mean it is the same) but at a much lower cost $7.60 per plug (the difference is the ground prong since the denso has a groove cut in the center of it). The NGK ITR6F-13 is also an irridium plug and a different ground prong but will cost as much as the Denso's.

I have yet to use NGK irridiums but there are others that have. At least now you have two options. Both denso and NGK have some good information on their web sites so you may want to read some of it before buying them. So far on two vehicles I have yet to run into any problems with the Denso plugs when they are gapped properly.

GA04COBRA
06-25-2006, 04:18 PM
to aussie:

i have a 2.75 pulley with efs solution tune and still have the stock plugs. it runs great with almost 38k miles. i did not even think about the plugs..thanks for the info...
also for folks wanting to use hand held programmers, think twice about the "hyper-tech"....i had one for my '03 gt 2-valve and when i sold it i set it back to stock and saved it because hyper-tech said it could be used on the 04 cobra. with only cat-back change & cai i tried the hyper-tech and under load it would detonate...i called hyper-tech and they did not have any explanation. but think about it...the same tuner for a naturally aspired 2-valve and a s/c 4-valve..i don't think so....

i, also, switched back to stock tune at one time...worried about reliability...but i missed that extra punch and after discussing with several folks, that know engines, i went back to my current tune...this motor is strong enough to handle up to 14# boost without any concerns.

ausie
06-26-2006, 07:54 AM
to aussie:

i have a 2.75 pulley with efs solution tune and still have the stock plugs. it runs great with almost 38k miles. i did not even think about the plugs..thanks for the info...
also for folks wanting to use hand held programmers, think twice about the "hyper-tech"....i had one for my '03 gt 2-valve and when i sold it i set it back to stock and saved it because hyper-tech said it could be used on the 04 cobra. with only cat-back change & cai i tried the hyper-tech and under load it would detonate...i called hyper-tech and they did not have any explanation. but think about it...the same tuner for a naturally aspired 2-valve and a s/c 4-valve..i don't think so....

i, also, switched back to stock tune at one time...worried about reliability...but i missed that extra punch and after discussing with several folks, that know engines, i went back to my current tune...this motor is strong enough to handle up to 14# boost without any concerns.
If your tuner was able to set up your car with the stock plugs your car would operate just fine as is. The stock Ford AGSF 22FM1 plugs have a similar design in the electrode tip when compared to the NGK ITR6F-13 with the exception of the electrode material. I have never seen a ford plug that looked like the one's I pulled out of my 04 Cobra. I was even contemplating why I even pulled them out. When I changed the plugs in my 01 to denso's I could tell the difference even after removing them and installing other plugs I went back to the used Denso's since the smaller electrode allowed for a slight advance in spark firing. I did not expect any change in performance in the 04 but I did (not a huge difference but it is noticable). The big difference is that pesky miss when cruising at low RPM went away and only happens once in a great while. Currently my 04 has the stock tune and pully. Considering your car is tuned, I am sure your tuner dialed in the timming with the stock plug in consideration. If the timming is advanced, changing to a faster spark response type plug may cause a loss in power if it causes too much spark advance (it all depends on how much was tuned into it).
If you are not experiencing detonation with the stock plug it may not be necessary to change plugs. If you have a CDI (capacitor discharge ignition) to boost the coil voltage then you need a special plug for that application to prevent damage to the resistor element in the plug of the stock or aftermarket plugs. The spark response of the plug does play a role in timming. If the plug can fire at a lower voltage that will increase timming slightly which may result in a slight power gain. The spark gap also is important in timming response. Too large a gap at higher boost levels will cause plasma (arc) blow out resulting in a missfire.

Some have cracked the insulators on aftermarket plugs when running high boost #'s and more than likely they are using the wrong plug for the application. I have seen the pictures in another forum of the Denso's insulator cracked. It is either a design flaw in the insulator, damage from shipping, or a result of thermal overstress since they were running more than 14psi of boost. Also, the type of ignition system was not disclosed so that may also have played a role in the damage to the plug. look into modularfords.com there seems to be alot of plug related issues in there. :thumbsup: