Ok I have a 2003 FX4 LVL II with a 4.0 V6 in it. The truck has about 57,000 miles on it. Recently I replaced spark plugs on the truck with NGK iridium spark plugs. When I was removing the old plugs I noticed that they seemed to be gapped a great deal more than the NGKs I was putting in it. I didn't pay much attention to it as the new plugs were already gapped at .054" and the manual to the truck said to gap at between .052 and .056".

Shortly after I changed the plugs I noticed that it started to sputter a little bit when I really pushed the pedal down. It is a 5-speed and when I shift into any gear and push on the gas it sputters and feels like it is misfiring until it gets going to higher RPMS. If I slowly push on the gas and don't try to accelerate hard it runs fine.

I've noticed this for about a month now and at first some days it would do it and others it wouldn't. As of lately it is doing it really bad. Driving home from the gym the other day it would hardly idle and died 6 times in 4 miles. Next day it started fine.

So here is what I am running through. I checked all the plug wires, which are also new. They are all hooked up right and appear to be seated on the plug just fine. I was thinking maybe some bad gas but I've run HEET and Lucas injector cleaner through it and the fuel filter was replaced only about 20,000 miles ago. I have a K&N air filter, could the oil from that have dirtied the mass airflow sensor? I have heard of that happening. Are they the wrong plugs? I was looking on the NGK site and noticed that 2 types of plugs are made for that year of 4.0 SOHC. Apparently there is a 4.0 V6 E SOHC engine and a 4.0 V6 X SOHC engine. The plugs for the "E" are gapped at .054 (which is what plug I bought) and the "X" is gapped at .065. Did I buy the wrong plug? How do I know which one I need. Would .01" difference make the engine run that crappy? Is the worsening condition a result of the wrong gap and carbon building up on the plugs? I am open to any ideas if you guys can help.

Thanks
Ryan

 

could be the MAF. try cleaning it. If you over-oil your filter it will mess up the readings for the MAF.

 

How new is the fuel filter?

 

A little less than 2 years old

 

I forgot what mileage the fuel filters are rated for but it isn't much. I would try cleaning the MAF and testing the coil. Also the X and E are in the VIN I believe. I'm not sure which ones I bought when I did the plugs 50K miles ago. Maybe one of the plug gaps was wrong from bouncing around in the box.

 

Any ideas on what plugs I should use, the .054" or .065"?

 

What you describe is ignition related. It could be plugs, wires, or the coil.

Since you changed the plugs and wires I highly suspect its one of those.


As far as the plug gaps go. The ground strap on some plugs (including motorcrafts) over time will "creep". Two things happen.
1) With heat cycles the metal tends to relax. Depending on the material it's made from and the grain structure the ground strap can pull away by up to 0.010"
2) Electrode wear. Over time small amounts of material are removed with a properly operating & heated plug.

And if your engine is "stock". Just stick with the stock gap.
Me personally.. I like to go with a ultra high quality plug and a unshrouded spark. But then again I shoot nitrous and need a stronger than stock spark. (I also narrow the gap down to 0.040)

btw, if for some reason the center ceramic of the plug gets cracked you can see what your seeing. A bad connection in the wires, a broken wire, or a old coil will do the same thing.

Rich

 

Scan for PCM error codes. You may have some misfire codes, that will tell you which cylinder is misfiring, or lean codes. Lean codes can come from a
contaminated MAF sensor, so try cleaning it. Also check to see if you have the correct plugs, the SOHC 4.0L V-6, and OHC 4.0L V-6 take different plugs.

 

Rich, I'm curious, what plugs (and material) "pulls away" by up to 0.010"???
The only way to create a grain boundary would be with a bi-metallic structure,
and bi-metallics ARE NOT used for ground electrodes!

Elecrode erosion (due the current flow B.T.W.) is the only mechanism I have
ever heard of that increases plug gap over time.

Are you no longer running Denso plugs? Because they have conventional
"shrouded" electrodes.

 

I have heard of people having problems with plugs in the 4.0 SOHC engine if they are not Motorcraft or Autolite plugs. I used Autolite double platinum plugs in mine when I changed them and had good results. I don't know if that is your problem but something to consider.

Another thing you might want to check out is the PCV tube connection at the throttle body. There is a 90 degree rubber hose that connects the hard PCV tube to the throttle body fitting. That hose degrades and causes a vacuum leak. I had that problem and it took a long time to figure it out. It is under the top radiator hose on the driver side of the throttle body. My symptom was a rough idle sometimes and if I let it idle long enough it would die. Once I got the rpm up, it ran fine.

 

Bob.. when plugs are indexed the spark *is* unshrouded. Lets stick to helping others. ok?

Rich

 

I noticed a pattern! Rich posts then Bob has to post. Rich I believe you have an idol/stalker.

 

He's definately got "issues" with me. I tried to resolve them off line. But he's unwilling to do anything except try to pick fights with me out in public forums. I wash my hands of him and am trying to just help where I can. IN this post ryan21c21 is having misfire problems.. and bob wants to turn it into a bash on rich thread.

Class act there..

Rich

 

I'm tired of seeing you post bad information Rich!! You claimed over and over that a dirty MAF sensor would not throw lean codes, but after that you made a post that you had a spec of lint on a MAF sensor throwing lean codes!!


And then you post the BS about the ground electrode material causing an increase of 0.01" in the GAP!! I'm tired of seeing your BAD information!!
Do you need me to explain grain boundaries to you?

You have posted that you will see an improvement with a K&N intake above 4000RPMS, but in another post, you say 5000RPMS!!! It comes down to when
you lie, you seem to forget what you said!!!

 

You think we aren't tired of seeing your crap. You lost my complete respect because you go around telling everyone aftermarket parts suck when you have aftermarket parts on your truck. Also you make comments on aftermarket parts that you have not tried on your own. Rich could straight out lie to my face and I would still trust him over you any day.

 

I think this is what you meant to say.............Rich can't handle it when
I catch him being technically WRONG, or in a lie........

 

Umm no. You can't handle it either. I have proved you wrong many times and all you do is change the subject. Remember when I proved you wrong about the Porsche?

And then there is the part where you have aftermarket parts on your truck. Its on your own picture website.

No answer yet again. What a sad little man.

 

I looked at the Motorcraft website and there are two types of 4.0 SOHC engines. An "E" code and an "X" code. I'm working on figuring out the difference and will let you know. I'm thinking I have the wrong plugs.

 

One thing I noticed and didn't like about the bosch+2 and my Densos is that the length from the conical seat to the tip / sparking gap area is shorter than my stock ones. Here is a pic of what I'm talking about. I aligned them by the conical seat (left side of pic) which shows the difference of how far each would protrude into the combustion chamber. At first I had a slight miss (or incomplete burn) when the motor was bone cold and accelerating up to 55mph. (my plugs are one range colder for nitrous and I would expect this) But after about 1000 miles it went away. We've been having 15deg mornings lately and it's been as smooth as silk whether I let it warm up or whether I fire it up and hit the road. I guess the length is not an issue? At least on my 06 it seems to work fine.

Rich

 

I have pissed with "better then stock" performance plugs in the past on differnet engines. Let me tell you, as long as your engine is stock, factory plugs are the way to go. Thats why they come that way from the factory.

My truck has almost 70K and sometimes sputters when starting but comes out of it. This spring before boat hauling duty I plan on a full tilt tune-up. Stock parts will do just fine thank you.

Nothing like paying extra $$ for more aggravation!

 

This is not true. The "factory" doesn't spec parts. Engineers do. As a OEM automotive engineer I spec off the shelf parts that meet a certian goal. And often times it's not the "best" because of cost. The real goal is not to make the best widget we can. It's to make the most profitable widget we can.

As for "value". (real or percieved) That's up to each of us for our own self.
Considering how I operate my ranger & how long I expect to keep it. There are not too many mods on my truck that I feel are of poor value.

Rich

 

Rich, one point you keep missing is the heat range of the plug. Motorcrafts
Are designed to be the exact heat range required for a particular engine.
The aftermarket spark plug companies try to cover many applications, instead of specific applications like the OEM plugs. One mistake you are making is running a colder Denso than is recommended, just because you
might shoot nitrous 1% of the time (if that much). That means you are running the WRONG aftermarket plug 99% of the time.
Just because you paid a extremely high price for the Densos, doesn't mean it's going to be a better plug! The iridium electrode on the Denso
is there for longevity, the same reason plug manufacturers use platinum on the electrodes.

Check out this URL from NGK:



http://www.ngksparkplugs.com/tech_su...x.asp?mode=nml

 

What you are seeing Rich is a difference in "reach". Obviously, the Motorcraft plug electrodes will
be placed into more of the air/fuel mixture, as it enters the combustion chamber.

Do you think Motorcraft made the plug longer to cut cost? This is an example where the Motorcraft was designed specifically, and optimized for the 4.0L. More than likely, if
Denso had made their plug that long, there would be applications where piston clearance would have been a problem.

And, as a secondary benefit of the Motorcraft plug, since there will be more spark plug protruding into the combustion chamber, this will raise the compression ratio slightly.
To find out how much, you would have to CC the head with each plug installed. But, this was taken into consideration when the Motorcraft plug was designed for the 4.0L.

 

Bob, you didn't conduct the DFMEA and neither did I. Let it go.

Rich

 

I sell parts for John Deere ( I know all about cost vs. performance ) Even a moster company like Deere will install a part because it's cheaper and should work and then latter it bites them in the ***. (Thank you parts venders)

That all being said ( to each his own ) what is the best spark plug for the 4.0 SOHC engine? Has anyone done any testing on this? I just read too many posts from those who install aftermarket spark plugs and have problems afterwards.