So after 100k miles i've gotten around to changing my plugs. NAPA sold me Bosch 7580 (HR 9 DCY) which is also what Bosch plugs website calls for and a few other sources on the net. The plugs that came out of the motor were Motorcraft AGSF 34EG which look a lot longer and have a gap of around 4mm. I did a quick search of this plug application and it lookes like it fits some Ford cars. What is correct? Both have the same thread pitch and use 5/8" socket. I bought the truck with almost 50k on it from a dealer used so who knows if they are original.
Any thoughts?

 

First of all, if the plug gap is 4mm, it must have run like crap.That's about .157". If you wanna go metric, ours will gap at about 1.3mm(.051). Gap it a little on the short side, it's only gonna get bigger. If you are buying Bosch platinum plugs, then don't. There are many posts on this forum, as well as my own experience, that tells me our trucks don't like those plugs. If you buy Bosch, buy the Bosch Super(they are just solid copper core). Otherwise go back with Motorcraft, or NGK. Much to many people's dismay, I run Splitfire's, and have had great results.Just my .02.

 

Howdy Toecutter (what a screen name by the way!)
Welcome to FTE and the 4.2 forum. Glad you found us and hope you stick around.
I can not speak as to whether or not the Bosch plugs you mention are an exact/acceptable replacement.
I can say this: I'd return them and by Motorcraft. That's my opinion.

 

Oh my silly me. Stupid question here. I don't run motorcraft plugs. I think a .052 gap is very strange and abnormal. I run Autolite 764 with a .034 gap, which is a normal gap for a plug.

Question is: I've looked in at least 6 different auto part stores and CANNOT find a gap guage that goes anywhere NEAR .052, so how do you gap them????????? When my chevy and dodge friends see that imprinted on my trucks fan shroud, they all start laughing at me and dissing ford for a misprint .052??? very strange indeed.

Tom

 

I run Autolite's also, with a .054" gap. .034" is something you want to run if your truck has a major power adder (supercharger/turbocharger/nitrous). The smaller gap essentially keeps the higher pressures in the cylinder from "blowing out" the spark before it can ignite the a/f mixture.

That's strange you can't find a gauge that goes up to .054...most I see go from about .020 all the way up to .1

You probably wouldn't hurt anything by running a .034 gap on a non-poweradder vehicle though

 

V6,

Yah, honestly I don't notice any difference whatsoever between the two. The 764's are a step colder plug. Nothing wrong with running a bit colder plug, especially in Florida. Plus, i've never been a big fan of those "platinum, titanium, uranium, plutonium" tip plugs. Personally, I think it's a gimmick just so they can charge you extra money. Regular old copper style plugs always seem to work the best for me on everything. And there is no such thing as a 'supposed' 100,000 tune up. plugs and wires need be changed way before that, even if they are 24K gold plated

Tom

 

I recommend uranium and plutonium tipped plugs ONLY if your vehicle came equipped with the flux capacitor option. They last for at least 100k miles and trust me...nothing is worse than being stuck in 1955 without enough plutonium to get you back

 

Ok McFly "hey you, get your damn hands off of her"

 

I prefer Glow plugs in my 4.2

 

Based on what, do the plugs and wires need to be changed sooner? Your personal opinion of older vehicles?

I pulled my plugs out at 50K. They looked new, so I put them back in. Still there at 84,700. Also OEM wires. No misfires, and mileage is the same as it ever was.

IHMO, the reason you change plugs is for electrode or insulator erosion, and or if they are getting fouled or dirty enough to change performance. If none of these things are happening, then there is no need to change the plugs.

Same goes for wires, they are changed if performance is degraded or they are arcing or shorting. You can test resistance with a multimeter. If they perform to specs and get the spark there, and the boots still snap in with a good click, then there is no reason to change them out.

Doing maintenance just because "well, we've always done it that way" is a waste of time and money. There is no reason to replace servicable parts on a good running truck before the manufacturer's suggested interval. 3,000 mile oil changes included as well, my oil analysis tells me that my truck doesn't need them. 5,000 is ok, last change at 5100 miles, 4 ppm iron and 0 ppm lead.

 

Bron,

I agree with you in most areas. Correct, if you have a multimeter and can check the resistance of your plug wires than that's great. However, MOST people often tend to neglect proper maintainence of their vehicle until they actually start to feel a considerate power loss. However, the rate at which the degradation of these parts is so slow that people usually don't tend to notice a difference until months after the parts needed to be replaced. Looking at it from a "Preventative Maintainance" perspective, and keeping in mind that not everyone knows everything about electrodes and insulators, it's probably a good idea to change your plugs and wires at 50K intervals. I've actually had people on this forum ask me what a plug gap is and that they've never heard of that term before. So not everyone is capable of removing all the plugs and wires and measuring the resistance with multimeters and examining each plug for wear, not to mention that there could be a non visible crack in the insulator inside the plug where it can't be seen. My suggestion was meant for the average truck owner, not mechanics or wanna be mechanics (such as myself .

You'd be suprised how many threads I've read where people sign on and ask for help because their truck is hesitating and getting poor gas mileage. I tell them to change their plugs and wires and after they do so they type back 'thanks for the help, that fixed the problem'.

So, in general, why wait until it's completely broken before you fix it. Replace your plugs and wires each 50K miles or less depending upon how you drive or if their is visible deterioration.

Tom

 

Brons,

No disrespect intended really. But the majority of this forum consists of regular everyday truck owners looking for help and speaking technical jargon such as this does not help them in the least.

Oil should be changed at 3K increments OR LESS depending on their driving habits and/or location. Changing your oil is the absolute best thing you could ever do to your motor. And for 1.49 per quart, unless your living in your truck cause your broke, it's certainly worth the money.

Tom

 

I could not disagree more, the new SM oils are better than ever before, even the dinos. 3,000 miles or less? That's from a bygone era. Where is the science behind your recommendation?

There's too much heresay and opinions in oil changes. I use oil that costs $1.07 per quart (Chevron Supreme 10w30) and a $1.99 filter (WalMart Super Tech), run it for 5000 miles, and I get excellent analysis reports. My analysis shop said I should try 7000 miles next interval. (this I don't recommend for the general public). Ironically, using Mobil 1 5w30 and Motorcraft filters, I got worse results, although they were still good results, just slightly worse than the Chveron/SuperTech combo.

I think everyone should do oil analysis. If I had a turbo car, I would probably think 3K was a reasonable OCI. But for easily driven 4.2 like mine, I'm going farther. If you flog yours at the track, then by all means stick with a shorter interval.

 

Ok, i'm not arguing with you on this subject. We've already been through dozens and dozens of pages of threads in this forum regarding oil and i'm not about to create another one. It's one subject that I'm truly sick of. I change my oil every 3K or less and could care less about oil analysis. It takes me 7 minutes to change my oil and 10 bucks and it's not worth it for me to put that much effort into oil analysis. It's easier for me to just change it and makes me feel better. So, analize away and enjoy I don't feel like discussing this anymore.

Tom

 

I suppose that's one way of looking at it. I would still want to do analysis once a year to get an insight as to what's going on in my motor, even with a 3K OCI. I especialy believe that the 97-98 4.2 should do analysis OFTEN to catch any antifreeze in the motor, they do test for glycol, and sodium and potassium elevations are also a good sign of antifreeze. But to each his own I guess.