Needs some opinions on misfiring...

[TiziteLayinLow]

my ls sport v8 (91k miles) starting misfiring (p0304 and p0307 engine codes) so i had a buddy change the plugs in it for me with autolite single platinum plugs which is what advanced auto told him to put in it. he took each coil pack and measure with a multimeter, they were all within 5.78V - 5.89V. he said the gaps on the plugs were extremely bad.. some of which where in 62 range and were supposed to be in the 44 .. so got those in and shut off the codes.

i drove for about 2 days and starting misfiring again and codes p0304 and p0307 (same ones) came up.

I called the dealership about the warranty figuring that it was either bad coils still or the valve cover leaking. she told me to make sure the plugs i put in the car were DOUBLE platinum and that it would make that much of a difference. is this true?

any advice is appreciated,

thanks, matt

 

[waltdeuce]

Take out all the plugs you've installed and double check if tips are clean? If they have oil, you may have a problem....time to replace gasket. If they're clean, could be the gapping that you talked about. If gap is fine, then could be your coils. Manual strictly recommends motorcraft parts ONLY (currently using both motorcraft plugs and coils). I don't think it'd make a difference on which spark plug you use, but you may want to stick with what the manual says.

What type plugs were on there before you replaced them? Were they dual-tips also?

 

[SoonerLS]

I'm presuming that the LS's ignition system is a high-energy system like that used on the 3.0L SHO and 3.8L SC V6es, and those required double platinums, or the electrodes would erode fairly rapidly. (The SHO also required particular plugs, because of the head design and the plu wells.)

The SHO/SC DIS system actually fired in both directions. The coil packs were segmented into pairs of cylinders, with the current going in through the firing cylinder, then out through the cylinder on the other side of that segment of the coil pack. As you can see, this requires that both electrodes be platinum; if the LS uses a similar system, then it would also require double-platinums.

 

[lsbit]

As suggested, check the plugs and plug wells for oil. If they are dry, you probably still have bad coils.

The stock plugs are double platinum. They may be the same plug as the SHO as the number looked really familiar when I replaced mine. I had an '89 SHO some years ago.

You don't HAVE to use platinum plugs, but the coils fire well and you will wear out the cheap plugs in a much shorter time than the platinums.

I personally would not use aftermarket platinum plugs. I have had nothing but bad luck with them in any car I have attempted to use them.

 

[SoonerLS]

The stock plugs are double platinum. They may be the same plug as the SHO as the number looked really familiar when I replaced mine. I had an '89 SHO some years ago.

I seem to recall reading that somewhere, but I haven't confirmed it.

I personally would not use aftermarket platinum plugs. I have had nothing but bad luck with them in any car I have attempted to use them.

IIRC, the Motorcraft plugs for the V6 SHO were actually OEM'd by NGK, but only the Motorcraft plugs were the correct height and allowed the plug boot to seal properly. FWIW, I had much better luck with Motorcraft plugs than with aftermarket plugs on my previous cars.

 

[TiziteLayinLow]

wonder where I can get these plugs? only the dealership? I guess I will call them tommorow.

the ones that I pulled out of the car were motorcraft NGK plugs.. and when I called the dealership they said on the 2000 it MUST have double platinums.

autozone, advanced auto, and napa all say single platinum, double platinum and so forth on their website for this car. I think advanced auto should give me a refund on the plugs seeing as though they sold me the wrong ones..lol

why is all the confusion about spark plugs...

 

[HyeLifeLS]

The double platinum plugs for LS in dealership cost $8.11 each, I had mine changed with coils on last week.

 

[SoonerLS]

autozone, advanced auto, and napa all say single platinum, double platinum and so forth on their website for this car. I think advanced auto should give me a refund on the plugs seeing as though they sold me the wrong ones..lol

why is all the confusion about spark plugs...

This isn't the first time, nor will it be the last. When I had to replace the plug wires on my '89 T-Bird SC, I had the local NAPA shop swear up and down that they had the wires. When I got there and opened the box, guess what? I don't think those wires would have fit the regular 3.8l V6, let alone the 3.8 SC; the connectors were completely wrong.

I also found several places that listed a distributor cap for my T-Bird and my SHO, both of which had DIS (Distributorless Ignition System)...

At less than $65, go with the Motorcraft plugs. This isn't a beater Hyundai or Chevrolet--it's worth the extra money to get the right parts.

 

[2001LS8Sport]

Ford has published bulletins about the plugs on this car. Use only the OEM replacement plug. You save yourself a lot of future headaches.

 

[sleddingguy]

Ford has published bulletins about the plugs on this car. Use only the OEM replacement plug. You save yourself a lot of future headaches.

Great, I just bought Bosch plat quad tips

 

[Pete02LSE]

Great, I just bought Bosch plat quad tips

That's cool...I used the regular Bosch platinums.

Sorry but...a car that is that finnicky over what plugs to use...that's just nuts. I've never heard of such a thing. I mean...sure...don't go bottom of the barrel with your plugs but...other than that...it shouldn't matter.

I'm currently running the +4s in my 99 Camaro SS and it seems to like them (no misfires...no loss in power...etc.). I know there are better plugs and for the next change...it will get them.

-Pete
02LSE

 

[2001LS8Sport]

That's cool...I used the regular Bosch platinums.

Sorry but...a car that is that finnicky over what plugs to use...that's just nuts. I've never heard of such a thing. I mean...sure...don't go bottom of the barrel with your plugs but...other than that...it shouldn't matter.

I'm currently running the +4s in my 99 Camaro SS and it seems to like them (no misfires...no loss in power...etc.). I know there are better plugs and for the next change...it will get them.

-Pete
02LSE

You would think it shouldn't matter....but it evidently does. Find a service adviser that's been around a while and he should be able to come up with what's out there from Ford about this. And it's not just the LS.

But here's the deal...the factory Motorcraft plugs will last upwards of 100,000 miles. There is virtually no horsepower to be gained by using any other plug. Why would you want to use anything but the Motorcraft plugs?