JMU-03-f150

alright fellas listen to this so I just got new spark plugs but the truck was still missing so after looking at it we tested it and it said that cylinder 7 was misfiring and to fix it would need a coil pack well when they tested it the check engine light was on but they turned it off now talking with the mechanic he said that fixing it would be quick and easy about a 30 minute thing as long as that check engine light doesn't get turned off so now I'm thinking I'm screwed because I don't know how to turn the light back on and I really don't want to have to pay extra just because of a simple thing apparently without the light he won't be able to run a diagnostic test to see which cynlinder exactly need for coil pack so could anyone help me possibly turn the light back on or just tips on general any info is appreciated l, oh and truck is a 5.4 triton

Brandmaner

In my experience if you drive the truck with a misfire the check engine light will come back on, on its own. It will have to be bad enough to throw a fault code. My truck has #3 misfire and throw a "flashing" CEL which is something you really don't want. But it did stay on solid so I could put a codereader to it. Within 4 hours (The time it took me to get to a codereader since mine happened on christmas eve) #3 and #2 were now misfiring. I took it to ford because I was running out of time to get it repaired.

It was just two coils on those cylinders I got it all fixed up and back on the road. If it was #7 misfiring before go down to your local parts store and get a coil pack (Get motorcraft if you can afford it as going the cheap route is what caused my #3 and #2 to go bad and cost me an extra $300 in fees and replacement parts... not worth it!) and you will be all ready to go! Swap it out and if that doesn't fix your miss it may be something else.

Which as I said the CEL comes on anytime the computer reads something not operating properly.

mbb

You lost the misfire data stored in mode 06 when cleared the pcm. And the code.

You also likely will need to complete a drive cycle to re-establish learned profile parameters before the misfire monitor works again. The 3 decelerations are whats important , 65-40, without touching brake. Foot off accelerator completely.

http://www.obdii.com/drivecycleford.html

It can vary a little by year I think. Google the obdii ford manual for you year. I think they are on a motorcraft website.Also note you need a minimum fuel level for misfire monitor to work as well. This is all explained in the obdii manual.













You dont need a CEL, the misfire monitor raw data in mode 06 can show what cyl is bad without throwing code. It can also show others that are going bad

This is why people always say " it worked for a few weeks, but now the light is back on,". The misfire monitor wasnt running if they cleared code. Sometimes it can take hundreds or thousand miles to accidentally meet conditions. Which is why you need to know how to intentionally activate it after clearing code or disconnecting battery.

JMU-03-f150

So you think he could still fix it with it off because I have had the light turned off before and it came back on but I don't think I'll have enough time to drive it till the light comes back on

mbb

If misfire monitor is active, it shows in the raw data, even if not eniough to trip code. A good tech will look at this

mh64

how would you go about solving this issue without a CEL. was going to start a thread on this matter today. believe I to am experiencing this. right around 42mph it hits, thought it was a U joint at first but it only happens in the 40-50 speed. mainly at 42mph. How would you go about chasing a bad coil? got 95k on the truck now and was just gonna buy bank 1 next time I get paid, then buy bank 2 the next But would like to solve it before then and dont know if anyone has a good method

PerryB

You've already read the code, change the coil. Who cares if the light is presently on or not? Did you replace the springs boots when you did the plugs. That is often the cause of misfire.

mbb

You use a scantool that reads mode 06 test data

If you have a smartphone, you can get a chinese bluetooth one for $10 and download an app.

mh64

thanks, Have to look on ebay for that haha. probably just end up replacing the coils anyway. However, as I was looking at all the brands on RA, I noticed they carry denso. for half the price of motorcraft I think I may give them a try and let people know how they work. I know i would be publicly shamed by a few guys on here for not getting the motorcrafts but ive never once had an issue with a Denso part. I mean Denso supplies toyota with most of their parts, ignition included, they are made in the USA, they have all the qualities of the motorcrafts, but havent seen anyone try them.

mbb

You dont think hundreds of other people havent tried everything under sun cheaper in last 19 yrs?

Let us know how long they last. Most of my coils are original at 227,000 miles. Ive replaced 2. Some guys here work on fords for a living, if they say dont use anything else....I wouldnt second guess. Things can change...but your just taking unnecessary risk.