i have a 2002 f150 5.4. i just replaced all coils and plugs. 600 miles later it started vibrating again at rpms under 2000. a diagnostic check revealed cylinder 1 and 3 misfire. after removing the coils and plugs they looked to be sparking good. there was no gas or soot build up on the plugs. can u tell me what might be the problem.
p.s. yes i did use the dielectric grease they sent with the coils but than again the spark plugs are dry and appear to be sparking.

 

What brand plugs and coils did you use? Did you clean the grease off the contact springs after greasing the boots?

 

i used motorcraft plugs and carquest coils...are carquest coils a bad choice?

 

Possibly. We recommend the OEM replacements from Global Automotive or Uneek Supply on Ebay. A full set of 8 is about $80 shipped.

Did you torque the spark plugs to 28 ft/lb? Factory spec is 15, and that, along with the use of antiseize, contributes to plug loosening and blowout.

 

Yea, that sounds like a greasing issue ie -600 miles later. Then again, I didn't know Carquest sold coils, -that's a new one. I like Carquest, I've used their machine shop plenty in the past, they have a nice set up. BUT, with coils, it's hard to trust any other unless they have been proven by the users of this site.

However, now your in a predicament, what do you do ? You have a low grade Misfire, the worst kind to locate. You have new coils, so you don't want to purchase another set, although, that's what I would do lol. I've chased these before and it's time consuming and no fun.

Try this first, - Speed up to 60 mph/ coast down to 40 without touching the brake. Do this twice. Find your misfire within RPM's/ hold @ low grade point for monitor detection. Wait for your monitor to flash CEL . Once CEL has flashed, you have set DTC on the KAM, -SCAN for faulty coil.

Sometimes that works , other times it doesn't. I've seen it work both ways.

If not, it's a guessing game. You can replace one coil at a time with a known good one. How do you know if ones good? You don't. Not without a stress test on a WDS. This is done at a dealership, the cost is more than it is for a new set of coils. See where I'm coming from? Thankfully new coils are cheap if you know where to go.

http://cgi.ebay.com/ebaymotors/ws/eB...=STRK:MEWAX:IT

 

The 2000 V6 Mustang I bought for my son had an intermttent misfire on cyl # 3 that got worse.
It was a bad injector.

 

That's always possible as well, just not as likely. But yea, you can't rule that out, that's for sure.

What would be great is if he could get the misfire monitor to pick it up. That would at least narrow it down to one cylinder, hopefully. From there it would be cake determining the problem.

EDIT:

Wait a minute! He has the faulty cylinders - 1 & 3. How did I miss that ! Yea , he has a coil problem most likely. Needs to run a fuel pressure test first, just to confirm it's not a delivery problem. Also needs to post the exact codes, that's important. After a pressure test, just swap things around to confirm the problem part. If the coils are the problem (that's got my vote), return to Carquest. Go over your install, I just wrote that up on this site somewhere lol.

 

thanks for all the help guys! i replaced those two coils. also my bro inlaw hear a whining noise coming from the engine on the passanger side. turns out i had a bad pcv valve on that side is it possible that that bad valve would be stealing air from them two cylinders causing the air to fuel mixture to be to lean as the diagnostic check said? and possible making them coils go bad?

 

unlikely. did you eve get any codes other then the p0301 code? if it was a vacuum leak bad enough to cause a miss you would have got a code. most likely the carquest coils are junk. its happened to me I bought a set of new moto blue coils and one failed days later then another one has failed with only 20k on it.