96 cobra missfire

[94GTHO]

Hey stangnet, i have a little problem. My girlfriend got this cobra not to long ago and it was running fine. THen one day it started getting a miss to it. There was no check engine light. So we threw some octane booster in it thinking that a lower octane gas might have been put in on accident. Seemed like it helped but then a few days later when we take it out again the miss is worse. Still no code. I took the plugs out and noticed that the passenger side plugs were different then the driver side plugs. I know this could be the problem and got new ones just havent put them in yet. Do you guys know of anything else it might be besides the wires? Just want some input. THanks

 

[tonytaylor85]

Ford was putting the platinum on either the center or ground electrode depending on where that cylinder was in the firing order and therefore on the coil polarity. Do the earlier mod motors use wasted spark?

 

[tonytaylor85]

What are the part numbers on those? Either way go back with double platinum plugs if long plug life is important. The part number should be your stock part number with a PP on the end instead of the single P.

 

[94GTHO]

that was confusing. the plugs on the left arent supposed to be in the car is what I was saying. The ones on the right are correct.

 

[tonytaylor85]

Those are probably the original plugs. They were using different plugs in each bank for most of the engines back then.

spark plugs - SNMA Forum

 

[98COBRA281]

copper > platinum

but they only last about 10k miles...so mine should last me about 4 years...lol

 

[tonytaylor85]

I wouldn't mind changing my own plugs every 10k but on the GFs car, I'd never hear the end of it. "didnt you just put spark plugs in it?"
"it acts funny at redlights"
"it takes longer to crank"

That said i have copper cores in mine.

 

[94GTHO]

So when I change out the plugs I am supposed to keep them 2 different ones. When I went to advance auto parts to get the plugs, it only called for the sp342 which was motorcraft platinum finewire. It never said anything about two different kinds. And also, with the old plugs, the ones on the left look like when tightened they would sit higher away from the piston then the ones on the right

 

[tonytaylor85]

Not sure about the length thing.
Platinum is not as expensive as it used to be. You only need the platinum on one electrode so ford only put it on one electrode. 4-6-8 plugs times millions cars means they saved several million dollars. The prices have come down and now they put the platinum on both electrodes.

 

[94GTHO]

so ill be fine when i put the one kind of plug in......sorry for sounding like an idiot. just want to get it right the first time. it is my girlfriends car after all

 

[tonytaylor85]

Yes. A double platinum plug should last another 100k miles if it doesn't have any other problems. Motorcraft plugs are well respected, Autolite a close second. Personally I dislike Honeywell who is the parent company of Autolite. Motorcraft double platinum FTW!

 

[tonytaylor85]

copper > platinum

but they only last about 10k miles...so mine should last me about 4 years...lol

These guys say not to on cars with coil packs. Coil on plug is fine.
Don't Use Standard or Single Platinum Spark Plugs with Waste Spark DIS Ignition Systems