Question...

"Tyler's SVT Focus Hates Him" (tylerssvtfocushateshim)
03/12/2014 at 18:50 • Filed to: None

Apparently I've been running the wrong spark plugs in my car for the last 10k miles. Could I done long-term damage to my engine?

Unbeknownst to me, the SVT cars run a much colder plug than stock Zetec engines even though literally every parts store and website besides the one above show them using the same ones. And I, in my infinite wisdom, stupidly trusted the counter jockeys to actually be informed, which of course they aren't. Hell, no one is: I've spent years on four separate forums and the amount of misinformation about our cars is staggering; on this spark plug issue every forum thread has a different recommendation, and even the most well-respected Focus parts website (screenshotted) shows the right heat range but the wrong part number according to Denso's website. The only way I know for sure that I'm running the wrong plugs is calling a Ford dealership and talking to the SVT associate, who then had to call corporate to get a straight answer because he didn't know either.

I'm not a panicky person but I'm worried about long-term damage: I know spark knock can wreak havoc on cylinder heads, which in my case, could be a car killer. Cosworth only built a few hundred extra heads for these cars (a lot of which were reserved for the Formula Ford teams) so if it goes there's almost zero chance of finding another. The car seems fine: I get good gas mileage, the power comes on clean and strong, there's no misfires or rough idle or anything out of the ordinary besides a bit of sluggishness after a cold start, which I attributed to the crappy PCM tune on the '03's. Should I be concerned or am I just freaking out about nothing?

DISCUSSION (7)

HammerheadFistpunch > Tyler's SVT Focus Hates Him
03/12/2014 at 18:59

Your car has knock sensors, worse case scenario is that you are down on power slightly. Frankly, this is a minor issue and I think you can relax.

desertdog5051 > Tyler's SVT Focus Hates Him
03/12/2014 at 19:17

Something that most mfg's/forums neglect to tell you is that it depends on how you are using the engine. When I drag raced Harleys, you needed a colder plug, but not as cold as you would need for circle racing. It is entirely dependent on the application. If you are mostly street driving with a few spirited drives and maybe an autocross or drag race here and there, you are good with stock plugs. Your knock sensors will tell you if there is a problem. Don't sweat the petty stuff.

Squid > Tyler's SVT Focus Hates Him
03/12/2014 at 19:24

You should be fine, just order the right plugs and put them in when they arrive. Too hot of a plug just means you get knock and at that point the knock sensors should throw up a flag and pull ignition and you should still be fine. You've done 10k miles so a few hundred more shouldn't be bad just be happy its still not hot like summer time, then there might be more of an issue.

Do you know how many ranges hotter the plugs you have in there now are compared to what SVT specs for the car?

Tyler's SVT Focus Hates Him > Squid
03/12/2014 at 19:46

I believe two, since the website above listed it as such. I asked the parts guy at Ford and he didn't know the range, just the part number.

Tyler's SVT Focus Hates Him > HammerheadFistpunch
03/12/2014 at 19:48

OK, that's what I was worried about. I've heard rumors of the wrong spark plugs destroying heads in these cars, so I overreacted a bit. I love this car and want to keep it running healthy for as long as I can, so anything like this just bothers me to unreasonable levels haha.

Tyler's SVT Focus Hates Him > desertdog5051
03/12/2014 at 19:52

Thank you for the reassurance. That's another reason I had such trouble finding information, it seems like everyone on the forums is running forced induction or have some crazy built motor with half the internals replaced. Even the guys with stock engines were divided on their plugs, some saying this part number, some saying that one, so it's a bit of a crapshoot regardless.

Squid > Tyler's SVT Focus Hates Him
03/12/2014 at 20:44

Order the correct plugs and just stay out of the throttle until you get the correct plugs in. You should be fine.