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What gap to run in spark plugs? 2004 ba xr6t


danielknox281

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Hey guys! I have just bought new coils and spark plugs (ford) the same as my car is running now, but I'm not sure what the previous owner gapped them to or if they left left them at .8 mm. Its running 20psi and a fair few mods so should I just go to a mechanic/tuner with my flash tuner and see what they think? Cheers :)

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Yeah mate you just take them out and use a set of feeler gauges to check. 

 

When you put the feeler gauge through the gap there should be a little bit of resistance but not too much. 

 

Be careful not to snap the porcelain part of the plug when you undo it or put it back in. There should be a rubber bit in your plug socket to centre and also grab the plug to remove it. 

 

Never remove a plug from an alloy head when it's hot as it'll be likely to damage/strip the thread. 

 

End of the day if you're running 20 psi and it's idling well and not breaking up under load you don't need to look at your plugs unless you're tuning like that, which you aren't.

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yeah sweet I found a little circle gauge that  I can buy and use. either way I have heard different opinions about gapping? it makes sense to gap them at 0.7 instead when running higher boost but some shops recommend other wise.

it dosent have much breakup under load or when its cold, but after its been hot it it has a single miss (when I got it) and now seems to miss on 2 cylinders. Even if coils and plugs dont solve the problem they are near 2 years old so need to be done anyway. also the miss clears out when the radiator kicks in?

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1 minute ago, danielknox281 said:

the miss clears out when the radiator kicks in

 

Hmm interesting. It'll be voltage related in some way but farks me exactly what though.

 

Plugs and coils are fairly cheap to do ie sub $300 and it's usually the first place to start looking when there are issues like you've described. Vacuum leaks can do that too.

 

I've heard that those circular thingies aren't very accurate but you could always check it with a set of vernier calipers before using it. I just use the blade type ones and again they are pretty cheap.

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yeah I worried it might be eletrical as it might be a pain in the ass to find what it is. I spose il know once theyre in and will look for other possibilities if it still misses. I cleaned out my throttle body the other day and checked my air filter too so im hoping its the coils/plugs.

ah okay well I have the tapered blade ones at home so if theyre more accurate I might try those!

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37 minutes ago, Puffwagon said:

It'll be voltage related in some way but farks me exactly what though.

18 minutes ago, danielknox281 said:

yeah I worried it might be eletrical as it might be a pain in the ass to find what it is.

 

I didn't mean that there is an electrical fault, I just meant that if it runs differently/better when the fans come on then there is something voltage related happening.

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Gapped the plugs to 0.7 and put the coils in too but its still missingthe same when its hot. It has had a smaller battery put in in order to fit the other mods and also has a sound system. But still sitson normal voltage when its running and hasnt had issues starting or anything. Not sure what to look for next 

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Well shucks.

 

This miss that is happening, is it cyclic or arrhythmic? Is it at idle or the whole way up the rev range?

 

It might just be tune related and need a bit more fuel at idle to smooth it out.

 

There is a whole bunch of things that can cause a miss but like I mentioned plugs, coils and vacuum leaks are the most common causes.

 

Apart from hitting up the search bar for a couple of hours to find stuff out, being a Friday, there should be a few more people logging on that hopefully leave their two cents to help you out.

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