I've ignored this for a while, but I think it's time I do something about it.

My wife's '98 EB 4x4 Expedition has a 5.4L engine that makes quite a bit of noise during acceleration. It believe this to be detonation. This forum has been invaluable in the past and I'm hoping to have the same luck with this problem. What can I do to stop this short of buying premium grade fuel?

As far as I know the spark plugs are stock. Is there another plug that would be better?

Is it possible the knock sensor needs replacing?

BTW, the engine has 128k miles and runs like a top...or a "knocking" top.

Thanks.

Rob

 

Does it stop when you use 91+ octane fuel?

 

does the same thing. If I run the mide grade gas (89 octane) it doesn't ping much. But on 87 it's terrible. I haven't tried 91+ but I'm guessing it would run even better. Just can't stomach paying 2.35 a gallon for the premium.

 

A gasoline's octane rating is only an index of it's resistance to detonation. A higher than recommended octane index only addresses your issue temporarily; it will not cure the problem. There are many factors that induce "pinging", but usually they're associated with a change in ignition timing and/or a change in compression ratio. Ignition timing is easy to address; a change in C/R is sometimes due to a carbon build-up in the combustion chamber. Is yours a recent/rapid change, or did the pinging build up slowly over a period of time? A recent/rapid change MAY indicate a "bad" batch of fuel. One time I topped-off 3 motorcycles and my '90 Supra in a 2-hour span at the same gas station/same pump. Detonation was immediate and SEVERE. I drained and re-filled (another station) the MC's; problem immediately disappeared. Topped-off the Supra every day until the "bad" fuel was diluted enought to stop the detonation.

Gradual long-term detonation MAY be reduced by adding some commercially available fuel-additive that states it'll reduce carbon build-up. Also, some vehicles' owner's manuals will state that some pinging is "normal" during even light acceleration; however, I don't think that's your problem. My 2 cents worth; hope it'll guide you to some solution. I'm curious to hear what others have to say.

 

I think there are a few things you could try -

1. If the sparkplugs are original, I'd think about getting them changed. Ford recommends 100k miles. I just did mine at 72k. If you have original plugs with that many miles on them, you could start burning out COPS. At $50-$100 each those aren't cheap to replace.

2. Try the seafoam treatment. That will help clean off carbon deposits on the valves and in the combustion chamber. There are other threads that explain how to do this if you need specifics.
-In short, get the engine heated up to normal operation temps.
-Shut the engine off & disconnect your brake booster vaccume hose & put a funnel in it.
-Start the engine and Pour in about 4-8oz (I used 8 oz) and shut the engine off quickly. Let it sit for about 10 minutes.
-Start the engine up and enjoy the white smoke show. That is the carbon deposits being burned off. If it's really bad, you may consider doing this a second time after a few trips to work or where ever. Don't be surprised if it's hard to start or runs pretty rough. It may even seem like it's missing for 30 seconds or so.

I just did this on mine a few weeks ago. I never had a ping but my engine seems to idle smoother now.

Good luck!

Dan

 

oh yah, wanted to add - I would not switch to a different brand of spark plugs. Seems like people have some success with certain after market brands, but the over all opinion is that the Motorcraft plugs allways seem to work good. The plugs are a PITA to change in the Expy so you want to do it right the first time. Took me about 4 hours the first time I did mine.

 

"vanlohd": I'm familiar with the "white smoke treatment"!!! Decades ago, I used to pour diesel-fuel directly into the carburetor (remember carbs?) of my air-cooled VW's. Guaranteed to burn-off carbon deposits in the cylinders!!! Had to pour slowly - if the engine quit, it was tough to get it re-started. And I'm talkin' huge, thick billows of white smoke. One time, my neighbor's wife called the fire dept. when I filled her back yard with smoke!!!

I too like the Seafoam. My father swore by the stuff while stationed in the Pacific during WW II: he says the Navy used it in every diesel and gasoline engine crankcase and fuel-tank in their inventory. He claimed it cycled his Browning automatic rifle faster and greatly reduced powder fouling. That BAR tip probably classifies as one of his "war stories."

"rguy": sorry to digress from your current problem.

 

thanks guys for the suggestions and comments.

as for the pinging, I can't say it has gradually increased because my wife drives it mainly. I only notice it when I drive it then quickly forget about it after I get out. My recent concerned has been prompted by the astronomical gas prices and a half hearted attempt to improve the fuel economy.

Since my arms are not that long and I am limited to 1 elbow per arm, changing the plugs will be my second option. Therefore, I'll try the sea foam method first. I remember hearing about this years ago but never lifted a finger to try it. I guess it's time. My only concern with this is the possibility of hydralic lock and bending a rod. How real of a problem is this? Because of the smoke, I should probably do it at night too.

BTW, what are the tricks to changing the plugs so I don't need a skin graph on my hands when I'm finished?

thanks.

Rob

 

Try a full can of Seafoam in the fuel-tank first. Don't expect much of a change until about 100 miles or so. The Seafoam also claims to act as a fuel injector cleaner; again give it a hundred miles (especially sustained highway driving). Clogged fuel injectors COULD also mean a lean mixture. A lean mixture is a hot mixture, and a hot mixture COULD be one of the cause of detonation. Unless I'm absolutely sure of a particular diagnosis, I usually start the cheapest/simplest approach then work my way up the cost/complexity chain. Good luck.