Misfire, no code yet

[GenesisGuy70]

Hi all

Replaced the original Motorcraft plugs in the car in my sig with NGK Irdium IX. Had them gapped wrong, took them out and regapped to original spec. for the engine.

Now on start up, I can feel the engine shuddering from misfires, this was never present before. They aren't misfiring enough to throw a code but it is perceptible. Not sure what to do, ignore it since no codes, or replace them with the OEM plugs, or gap them back to the .54 they are spec'd at by NGK (vs. the .35 spec'd by Ford on their OEM plugs).

This engine used to purr like a kitten. Not even the slightest shudder.

The intake does have to be taken off for this 3.5, not sure if I didn't get the torque on the intake gaskets right but if anything they're over-torqued, the torque wrench I had stunk. I didn't replace them because they had only been on for like 6 months before I had to take it off to re-gap.

 

[another Todd]

I'd go back to NGK spec. IR plugs can run a wider gap (due to their finer wire center electrode) which is beneficial to ignition of the mixture.

 

[bubbatime]

Electronics are so sensitive in modern cars, I have always used the OEM plugs for the past 15-20 years. Wasnt such a big deal back in the early 90's and earlier, but cars just seem to run ideal on the OEM plugs.

I'd go back to the OEM plugs and chalk it up as an expensive lesson learned.

 

[bdcardinal]

Use Mode 6 on your scan tool to check for misfires. My '14 didn't have any codes, but I had one of our techs look and they were present in Mode 6.

 

[Quest]

If yours are spark plug cable type, consider back-tracing the steps that you took (and replace the spark plug cables with fresh new, high quality ones).

If yours are coil-over-plugs type, consider getting new, OE replacement.

Q.

 

[circuitsmith]

Hold up a Motorcraft plug next to the NGK.
Do they have the same distance from the mounting flange (+ washer) to the gap?
IOW the same projection into the head?
Just curious.

+1 to OEM being the safest bet for plugs in a stock engine.

 

[SwampSurvivor]

Have had numerous Fords ... they never throw a misfire code when a coil (inevitably) dies.

 

[GenesisGuy70]

Originally Posted By: Quest
If yours are spark plug cable type, consider back-tracing the steps that you took (and replace the spark plug cables with fresh new, high quality ones).

If yours are coil-over-plugs type, consider getting new, OE replacement.

Q.


This does the coil-over-plug, do you mean getting replacements for those or the plugs? The C-O-P's are not cheap at all.

+1 to being an expensive lessor learned. I've had a lot of those lately.

The Iridium's were $7/each. The OEM are $2/each.

 

[KrisZ]

It could also be a vacuum leak from the IM.

 

[Kuato]

Go back to the original plugs. Several engines (notably the Jeep 4.0) run poorly on expensive plugs and do much better on OEM or the inexpensive replacements.

 

[CT8]

Lets see the engine was fine before the plugs were changed? Hmmmmm what could it be???

 

[PandaBear]

Originally Posted By: KrisZ
It could also be a vacuum leak from the IM.


that would be my guess as well.

 

[Oregoonian]

Recently changed my plugs on my 03'Ford Focus......with Autolite Double Plats(APP 103). They worked perfectly and much cheaper than the Motorcrafts.

 

[GenesisGuy70]

I don't think it's the intake...but I guess it could be. I think I'll just re-do the whole thing. Back to OEM plugs and new gaskets.

Not happy about it though.

 

[GenesisGuy70]

Done and purring like a kitten again.

OEM from the start from now on.

 

[Vikas]

Alright, we got one more convert in our camp!!

 

[GenesisGuy70]

Originally Posted By: Vikas
Alright, we got one more convert in our camp!!


Woo woo! Oh yea!