You are right, I think you'll get about a 5hp boost with premium fuel in a modular engine. I think I also know why it is a "undocumented" feature. If you design an engine to use two types of fuels (unleaded and premium) you have to certify your fuel economy at the lower value. So, running premium will give you more power (under load!) but may burn more. So, since fuel economy is not a truck's best characteristic, we don't want to make it worse by certifying with premium fuel.

As for the pinging, I have driven many trucks with 87 octane and don't notice any pinging. Are you sure you aren't hearing the exhaust system expanding?

 

Also, while I was waiting for my beast, some poor gal was there complaining about her Escort vibrating at idle. The shop foreman came out, got in the car started it up and said "that's normal" for the Escorts..maybe,
I've never driven one, BUT

I wonder how many Ford service writers and Ford mechanics say "That's normal" in one day ??

 

I think service writers and mechanics learn "thats normal" to get out of warranty work.

However, an escort that probably had a 4 cyl engine may vibrate at idle. Many 4 and inline 6 cyl engines do vibrate at idle.

The V in V6, V8, V10 etc. takes much of the vibration out and also produces more power.
Henry Ford put 2 4 cylinders together when designing his first flathead V8.

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97 F-150,4.6, Reg Cab, Flareside, Air Aid Kit, TransGo Shift Kit,
Superchips, Gibson Single Cat Back, ******* Bed Cover,
EGR Bug Shield, XL Full Length Running Boards,
Hellwig Rear Sway Bar, Hellwig 2500# Overload Springs

 

Looking at the principle, without adding balance shafts and other features to reduce vibration, an inline 6 can only be improved upon by a flat-6 or a boxer engine (180 deg V). So, the best angles for a 6 cyl engine is first 180 and then 0. The same goes for a 12 cyl engine.

 

When I took it in they asked me what octane I've been running. I told them 87 until this problem came up and then I tried one tank of 89 to see if it would take care of it. They said 89 would cause this problem. I find that one tank of 89 would cause any problem (especially this one) real hard to believe.
They did find the PFE voltage off a little bit and installed a new sensor but that did not have any affect on the ping.

The second dealer wants me to try a different brand of gas for 1/2 tank then bring it back in if the ping continues (which I'm sure it will).

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99 F150 5.4 4x4 ORP 3.73 styleside deep wedgewood blue ..no mods (yet)

 

What exactly is this exhaust expansion ? I took my truck in to the dealer for a pinging noise (especially noticeable in OD with light acceleration) and they said it was the exhaust expansion. IT SOUNDS DISTICTLY LIKE A PING TO ME. After I told him that he said "oh, all of them ping a little, that's normal". I'm really getting fed up with this **** ! I'm going to another dealer this afternoon to see what brilliance they will come up with..

Thinking I should have gone with the T100 !



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99 F150 5.4 4x4 ORP 3.73 styleside deep wedgewood blue ..no mods (yet)

 

The dealer who told you the 89 octane fuel would cause the problem is full of it. I have been running 89 octane fuel in my F-150 for over 2 years and the engine doesnt so much as gurgle.