Spark Plug Help
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Spark Plug Help
Hello all,
I've got a 97 f-150 4x4 with 4.6l engine. My ongoing problem is gas mileage ranges from 11 in town to 13 freeway.
I was complaining about this at the local Schucks and the counter person said pull a plug and bring it in for me to look at. To make a long story short, they said I was running the wrong plug. I had autolite APP764 and they said I should be running the APP104's.
With the price of a tune-up running about $200, I need help knowing if it's worth changing the plugs. Can I expect to see an increase in gas mileage and power?
What kind of mileage is everyone else getting with similar set-up?
thanks for any help.
I've got a 97 f-150 4x4 with 4.6l engine. My ongoing problem is gas mileage ranges from 11 in town to 13 freeway.
I was complaining about this at the local Schucks and the counter person said pull a plug and bring it in for me to look at. To make a long story short, they said I was running the wrong plug. I had autolite APP764 and they said I should be running the APP104's.
With the price of a tune-up running about $200, I need help knowing if it's worth changing the plugs. Can I expect to see an increase in gas mileage and power?
What kind of mileage is everyone else getting with similar set-up?
thanks for any help.
Moderator
Joined: Dec 2001
Posts: 22,436
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From: Louisville,Ky.
Hi and welcome to FTE 
Did they show you the difference in the plugs?
How worn are the plugs in it? Check the gap compared to what it should be. If it is too wide, it could cause some problems.
The gas mileage sounds a little low, but not far off really. This time of year, mine has lost about 1.5mpg due to the winter blends of fuel. My 5.4 is getting about 12.5 in town.
Jimmy
Did they show you the difference in the plugs?
How worn are the plugs in it? Check the gap compared to what it should be. If it is too wide, it could cause some problems.
The gas mileage sounds a little low, but not far off really. This time of year, mine has lost about 1.5mpg due to the winter blends of fuel. My 5.4 is getting about 12.5 in town.
Jimmy
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Hi lxman1,
My old plug was dark and they thought it looked okay for wear and the gap seemed okay.
However, the big difference was the old plug was only threaded about halfway up and the recommended plug had threads going up approx twice as far. So it seems that the new plug would be sitting deeper in the cylinder.
THanks for any thoughts.
My old plug was dark and they thought it looked okay for wear and the gap seemed okay.
However, the big difference was the old plug was only threaded about halfway up and the recommended plug had threads going up approx twice as far. So it seems that the new plug would be sitting deeper in the cylinder.
THanks for any thoughts.
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Oh, I forgot part of the story.
Apparently, there were some calls made to autolite concerning why their 2001 parts book recommended the APP764 and the current book recommends the APP104.
I understand that autolite claims they are exactly the same plug and only changed the recommendation because users didn't like only half the threading.
Does this sound reasonable? It seems there would be more stuff underlying a change in recommended plug.
thanks
Apparently, there were some calls made to autolite concerning why their 2001 parts book recommended the APP764 and the current book recommends the APP104.
I understand that autolite claims they are exactly the same plug and only changed the recommendation because users didn't like only half the threading.
Does this sound reasonable? It seems there would be more stuff underlying a change in recommended plug.
thanks
Senior User
Joined: Nov 2003
Posts: 263
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From: Royal Palm Beach, Fl
I just replaced the orignal plugs at 112,000 miles on my 98 4.6L F150 2WD. I used Autolite APP104. The in town milage when back up to 16 (same as when it was new) I have not checked the highway milage yet. It's running much smoother now too.
Posting Guru
Joined: Jun 2003
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From: Houston, Texas
Do not take your vehicle to a shop to replace the plugs. Replace them one at a time (do not remove more than one wire at a time). Pulle out the old plug and insert the new one. It's as easy as that.
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Senior User
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From: Hawaii
I can understand spark plugs causing you to loose so much. I'd look at other things causing it.
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From: Louisville,Ky.
If they didn't sit down in the cylinder as far as they should, you will lose compression due to the added space in the combustion chamber.
Also, a worn plug with more than recommended gap will be harder to fire and less efficient.
A better hotter spark will make more power, thus, be more efficient due to a more complete air/fuel burn.
Jimmy
Also, a worn plug with more than recommended gap will be harder to fire and less efficient.
A better hotter spark will make more power, thus, be more efficient due to a more complete air/fuel burn.
Jimmy
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What I don't understand is the real reason autolite changed the plug. It seems that performance or other technical reasons would drive a change in plug specification, not complaints of funny appearance.
I never saw what the original motocraft plugs looked like, does anyone remember the thread depth on the orig equipment plugs?
thanks
I never saw what the original motocraft plugs looked like, does anyone remember the thread depth on the orig equipment plugs?
thanks
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From: BC Canada
I'm just trying to change the plugs in my 98 4.6 and there are motocraft AWSF 32PG plugs from factory. They only have about 7 threads on them with a long grip before the flange. I never looked at the autolites but the cross to bosch, champion, and one other all show a plug with twice the threads. I tried one hole and it didn't like it. Just went in about 5 threads and stopped. I didn't persist, just backed it out and ran to the computer. Guess I should have gone with the autolites first. Anyone else had this problem?
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Hello all,
I had a diagnostic test run a few days ago and everything came up perfect and was told that changing the plugs would not make a difference (I had early installed the formerly recommended autolite APP764).
I ignored the advice and had the APP104's installed today and noticed a SIGNIFICANT increase in performance. The auto shop had a few problems getting the #8 plug to seal correctly and the compression gas was blowing the spark plug wire boot off.
It seems worthwhile for anyone who isn't getting the mileage or performance they expect to check their spark plugs. If you've got the 764's might want to replace with the 104's. If you're doing this yourself, you may also want to consider using motorcrafts to avoid the defective plug problems.
I had a diagnostic test run a few days ago and everything came up perfect and was told that changing the plugs would not make a difference (I had early installed the formerly recommended autolite APP764).
I ignored the advice and had the APP104's installed today and noticed a SIGNIFICANT increase in performance. The auto shop had a few problems getting the #8 plug to seal correctly and the compression gas was blowing the spark plug wire boot off.
It seems worthwhile for anyone who isn't getting the mileage or performance they expect to check their spark plugs. If you've got the 764's might want to replace with the 104's. If you're doing this yourself, you may also want to consider using motorcrafts to avoid the defective plug problems.
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Just made a couple of trips with the new plugs and was pleasantly surprised to on one freeway trip to Portland (approx 100 miles round trip) I got a little over 17 mpg. I also took a 180 mile ski trip (approx 60 miles in 4-High) where we lugged along for about an hour shifting between 1st and 2nd gear because of road conditions and got a little over 14 mpg.
The new, deeper seating spark plugs have made a substantial difference in this truck.
thanks for your input along the way.
The new, deeper seating spark plugs have made a substantial difference in this truck.
thanks for your input along the way.
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