Spark Knock
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Tuned
Joined: Dec 2005
Posts: 424
Likes: 2
Spark Knock
I own a 98 F-150 with 4.6 and 146K miles. I have noticed a spark knock at RPM's above 2500. The truck has been well maintained since I bought it but I don't remember having this problem in the past. I run 87 to 89 octane but hate to buy the good stuff unless I have to. Anyone else having this problem?
Thanks
Thanks
Moderator
Joined: Dec 2001
Posts: 22,436
Likes: 17
From: Louisville,Ky.
Could be carbon build up in the engine. I believe some of the 97-98 trucks needed the PCM reflashed to readjust the timing advance to keep detonation down. Is it happening at WOT or part throttle?
Junior User
Joined: Nov 2005
Posts: 78
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i had the same prob on my 97 4.6 was told toreplace the maf, but found i could clean the little resistor on the air inlet, been told that contact cleaner(elctrical partscleaner)
hopeit helps worked for me and cheap fix
hopeit helps worked for me and cheap fix
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Tuned
Joined: Dec 2005
Posts: 424
Likes: 2
I hate to show my ignorance but does that stand for Manifold Air Flow? When it was serviced by Ford at 100,000 miles the check engine light was on and what they found to be the problem was the throttle body needed to be cleaned and that took care of the problem. Is the MAF sensor easy to get to and easy to clean?
Thanks,
Thanks,
Hotshot
Joined: Aug 2002
Posts: 12,679
Likes: 15
From: BC, Canada
MAF stands for Mass Air Flow.
For some instructions and a picture take a look at https://www.ford-trucks.com/forums/s...hreadid=126093 and http://www.clubfte.com/users/racerguy/ResizeofMAF.jpg
The instructions aren't exactly right for this engine but you'll get the basic idea and the picture will show you more.
You'll also find more info if you search in here.
For some instructions and a picture take a look at https://www.ford-trucks.com/forums/s...hreadid=126093 and http://www.clubfte.com/users/racerguy/ResizeofMAF.jpg
The instructions aren't exactly right for this engine but you'll get the basic idea and the picture will show you more.
You'll also find more info if you search in here.
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Tuned
Joined: Dec 2005
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Man you guys really know your stuff! I am going to check this out and see if it will cure the problem. I'll keep you posted.
Thanks again.
srb1194
Thanks again.
srb1194
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Thread Starter
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Tuned
Joined: Dec 2005
Posts: 424
Likes: 2
Originally Posted by Racerguy
MAF stands for Mass Air Flow.
For some instructions and a picture take a look at https://www.ford-trucks.com/forums/s...hreadid=126093 and http://www.clubfte.com/users/racerguy/ResizeofMAF.jpg
The instructions aren't exactly right for this engine but you'll get the basic idea and the picture will show you more.
You'll also find more info if you search in here.
For some instructions and a picture take a look at https://www.ford-trucks.com/forums/s...hreadid=126093 and http://www.clubfte.com/users/racerguy/ResizeofMAF.jpg
The instructions aren't exactly right for this engine but you'll get the basic idea and the picture will show you more.
You'll also find more info if you search in here.
I never doubted your diagnosis. I cleaned the MAF sensor today and the problem is 90% gone. From a dead stop if I hold wide open throttle I don't hear any spark knock until about 4700 rpm in 2nd gear which equates to about 80mph. I feel that if I had better fuel in the tank I wouldn't even hear that. I am very pleased with the repair. I did remember that I had changed to a K&N filter about 10K ago and I think that oil in the air filter may have caused the contaminats to stick to those tiny filaments. Thanks again for all your help! When I get this darn XM radio installed I'll be through for a while.
srb1194
Hotshot
Joined: Aug 2002
Posts: 12,679
Likes: 15
From: BC, Canada
Good to hear that you had some success
If you ever have your truck in to your dealer you might want to ask them about reflashing the PCM like Jimmy (LXMan1) said too. Unfortunately Ford doesn't always tell us what the reflash does but it may cure the rest of the ping.
If you ever have your truck in to your dealer you might want to ask them about reflashing the PCM like Jimmy (LXMan1) said too. Unfortunately Ford doesn't always tell us what the reflash does but it may cure the rest of the ping.