TOMMY01GT

When I got my car it had a blown out plug, I fixed it and all is well. I know the other 7 plugs need to be changed and probably the Coil packs as well just for the fact it has alot of miles on it.

What can I do to make the plugs least likely to pull out the threads, and also least apt to blow out the new plugs?

Like..WD40 down the plug holes the night before, compressed liquid CO2 on the plugs to contract them? Anything I can do?

cliffyk

Just take them out with the engine cold (not run for 5-6 hours).

Unless they are not fully seated WD-40 or any other lubricant won't get to the threads (how would it get past the tapered seat?).

CO2 has no liquid state at pressures below 75 psi and boils immediately upon release from that pressure--even if it was liquid you would likely not be able to confine it to just the plug and as the aluminum head would contract more than the steel plug body it would just wedge them in tighter.

To preventing more blow-outs, buy a 1/4" drive torque wrench like this one from HF and tighten them to 150 lbin (12.5 lbft).

While you are there pick up this extended plug socket and a 1/4" female to 3/8" male adapter. The extended socket won't cant when removing the plug (applying uneven pressure to the threads), and makes aligning and starting the new plugs a piece of cake...

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If the COPs are firing the plugs without misfires under heavy load then there is nothing wrong with them and they don't need to be replaced. My brother has 185k on his '99 with all eight of the original COPs.

If you want to test them get one of these and open it up to 1/2" or so.

Pull the fuel pump fuse, #14 in the battery junction box, start the engine, and run it 'til it dies. Then hook the tester to a COP and ground and have someone crank the engine--if it can spark across the 1/2" air gap there's nothing wrong with the COP.

Don't let it spark more than 2 or 3 times or you will burn out the COP.

TOMMY01GT

Thanks Cliff. I just know that the COP's are old and original parts. I do have a slight miss sometimes, its barely noticeable, Im figuring old worn plugs.

I want to put in 8 new Flowmatched injectors and 8 new plugs and boots, and new coils, to me its alot like doing plugs, wires, cap and rotor on a conventional ignition system. Why wait for one to burnout...unless the OEM coils are better than aftermarket?

H0SS302

OEM coils are better than aftermarket.

TOMMY01GT

wow, thats rare.

jrp1588

Thanks for the tips, I've been meaning to change my plugs for the past few days, but I haven't had a free morning to work on my engine while cold. I considered picking up some PB blaster to loosen them up, thanks for letting me know I won't need to waste any of that. haha. I already have that inch/lb torque wrench from harbor freight, so I guess I'll just need a 1/4" to 3/8" drive adapter.

Would it be bad to put a little more torque into it? 15ft/lb perhaps? Seems like if it's a little tighter they'd be less likely to blow out.

jtb727

JRP1588~~They have blow out problems when over tightened, the heads have minimal threads, so tightening the plugs passed spec just put a lot of stress on the few threads you do have, and this is when plug blow out often occurs...

69MustangCoupe393cid

Not really. Aftermarket stuff is a lot of times of worse quality than stock. Ever wonder why Dealer parts are so expensive? There's a reason other then the fact that they jack the prices up. But then again there are also different "better" definitions.

cliffyk

People are running 600+ rwHP on the stock COPs, read the COP sticky for more info.

I would replace the boots and conductor springs ($3 a pop here), it is breakdown/flash-through of the boots that causes to COPs to fail.

It's just a HV transformer and if not overloaded they will last forever, like neon sign transformers. They only blow when the electrodes in the tube corrode from impurities in the gas and/or the tube not being fully cleaned and evacuated before being charged. When the ionisation voltage goes way up the transformer overheats and burns out.

If you really want to buy new COPs then go for it but don't expect any performance improvement from them.

Your '03 GT has 21 lb/h injectors which are just a bit too low capacity, operating at 85%+ duty cycle at WOT when stock, and close to 90% with intake tract improvements are made (the stock upper plenum is the weak link). If you are buying injectors you may want to look at the FRPP 24 lb/h units. They have been discontinued by FRPP however are still available from some vendors, make sure you get the ones with the Jetronic/Minitimer connectors.

The tune does need to be altered to run these¹, however the benefit is that they will be operating under 80% duty cycle letting the PCM better control high rpm/load fueling, and providing some headroom.

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¹ - The low and high injector slopes, injector breakpoint, and minimum pulse width need to be changed.

lizzyfan

That goes for coil packs too