i did the L swap(well, harley) on my expedition back in feb. now my sister uses the truck for her daycare, and i user her windstar. anywho, the truck is programmed for premium(not sure if he did 91 or 93). my questions is if she happens to have a lapse in judgement and puts in regular, how bad will that be? she usually only puts in $20-$30, which right now doesn't amount to much(6-10 gallons{28 gallon tank}) with premium being around $3.30/gallon, but i still don't want to buy a new motor. i put seafoam in the crankcase and fuel tank today, as i am trying to clean the motor some before i drive down to fl in 2 weeks. i want to add the 5oz(1/3 can) into the main vacuum line as well to get the rest of the engine clean and create a monster smoke show....but not sure which line it is. some insight on that please? thanks.

 

Don't know, or ever heard of seafoam, I've stayed clear of any cleaning additives do to bad experiances on some of my old high millage vehicles. an 03 motor shouldn't need it anyway.
A regular 87 octane mistake will damage the motor period due to detonation, it may not go boom right away but it will hurt it passed anything in a can, can fix,
and with 12lbs boost I would be keeping 93 in it for the same reasons listed above

 

very bad idea to put regular octane fuel in, it will detonate and could pop the engine if it is under load.

as for sea foam, while the truck is running unhook the brake booster hose keep your finger over the end or the truck will die, then allow the vacuum to suck the sea foam into the line a little at a time and your good to go.

 

I filled my L in 2001 with a full tank of regular; it was fairly new, it had no mods whatsoever.
Only after I did it, did I realize to my horror of what I had done, it did idle somewhat rougher.

I did not dare go to WOT on that fuel mixture, and it did ran a little harsher (mild misfire, and coughing) with no lasting ill effects.

Now; if I would ever do it once more (“NOT”) after almost 7 years, I would just add four or five gallons of Xylene, that would kick it in the butt….

 

I'd bring the timing way down if you have control of it (to like 10 degrees) and tell her not to use much throttle.

 

I wouldn't worry about it, unless you get into the boost. Our cr is 8.4 and detonation won't occur with it. With boost it's a whole different story!!
Just my .02
Bryan

 

+ 1 ^^^

If you stay out of the boost, no problem....

If you are really concerned, take it for a spin yourself. Leave the O/D off, get on the Interstate and run it up to 75 MPH. Set the cruise and in 2 hours, you'll have plenty of room in the tank for some 93....

 

Well guys all good ideas "IF HE had the Truck" and it was a 1 time deal. the post says "His Sister has it, using it for Her Daycare". and was asking what happens if she forgets and puts in Reg. so what can happen to his truck between her "possible" mistake and him finding out, which might be as he jumps on it

 

BOOM!!!!!!!

 

Exactly !!

 

Do you have a carbon build up problem in your combustion chamber ??? Thats what seafoam helps remove...carbon...

The monster smoke show seafoam creates is not the crude or carbon in your engine. The smoke is the 60% pale oil and naphtha in the seafoam. Seafoam is formulated to remove carbon build up... not "clean the motor". The supercharged 5.4 has no problem with carbon build up so running seafoam through the brake booster into the oily intercooler and intake valley and finally to the combustion chamber is not going to help do anything but clog you cats...... If you decide to do it anyway, make sure you immediately change the oil and check your spark plugs.

I would use seafoam through the BB on any other vehicle make that has a carbon build problem... and I have with success.

On your other question, tell her to drive it easy and listen for pinging.... it will be fine if she does not go WOT in 2nd or 3rd or OD.

take a minute and read this
http://blizzard.rwic.und.edu/~nordli.../gasoline.html