I have an '03 with the 3.0 flex fuel engine that has spark knock under lite load at highway speeds.

I have searched and found that MANY of the FF 3.0s are doing this.

All the info I've read is older, so I'm wondering if there is something current that I can do to fix it.

I have bumped up to premium fuel which is super stupid and expansive for this little engine.

Just don't want to do any permanent damage due to the spark knock.

Suggestions?? fixes?? stuff to try?? Thanks!

 

Assuming no codes...im fighting the same thing. I dont have any answers. Just letting you know you are not alone.

 

Make sure you don't have any trouble codes stored, or any vacuum leaks, clogged up PCV valve, dirty MAF sensor, wrong heat range spark plugs, overheating condition.

If all is well with the engine, I've used Techron Concentrate Plus in 2 vehicles with two different kinds of engines, to successfully address carbon deposit issues. One is my 99 4.0L pushrod & the Daughters 2014 Kia 2.4L GDI DOHC engines.
The 4.0L Ranger suffered early on with startup "marble noise" which Ford developed a "decarbon" TSB for. It worked, but only temporarily. So I developed a procedure that work's on the 4.0L Ranger & last year on the Kia 2.4L & lasts.

Run most of the present tank of fuel out & add 1oz/gal of Techron Concentrate Plus at the pump before filling, so you get good mixing, with a fuel that already has some PEA in its ad pack, like Chevron, Texaco, Caltex, or now Shell. This will raise the PEA treat level 10X above that of the pump gas alone & will usually tidy things up in one treatment.
Do daily spirited rpm runs at 3500 rpm for three miles or so as Ford specified in their 4.0L decarb TSB, or if you can't do that, anytime your getting on the interstate wind it out at 3500 rpm for as long & as many times as you can & run most of the treated tank out before refilling.
The PEA will soften up the carbon deposits & the high rpm & heat will help remove them. The Techron can tidy up fuel injectors, intake valves on port fuel injected engines, piston crowns & heads.
Do this just before an oil & filter change & let us know how it goes.

 

Thanks so far!!

I know I'm not alone.

I have cleaned the MAF, reset the computer, replaced the PCV valve, and about 95% sure its not running too warm,cooling system very clean by last owner, thinking of putting in a 180* TStat........Running a tank of BP premium fuel and 2 cans of SeaFoam right now, and romping on it a bit to clean it out.......gonna run it real low and fill with regular 87 octane and reset the computer again and see what happens.
The higher octane fuels are just a temp fix, these little motors surely don't need 93 octane fuel!!

 

Lets think about this some more. Your over doing the fuel & fuel treatment thing. Look in your owner manual & see that Ford doesn't recommend we use premium fuel. Our engines aren't designed/compression ratio, nor timed/valve/spark, to properly use premium, so with an incomplete burn, it can leave combustion chamber deposits we're trying to remove.
Same for over treating/double dosing with fuel additives if you've added Two cans of Seafoam, to One tank of fuel. Even though we mean well, if some is good, then more is better, isn't a sound idea for us to follow. Use the mfgrs prescribed dose ratio. EDIT: If you've double treated one tank of fuel with Two cans of Seafoam, refill the tank with untreated gas at the halfway mark & you'll be closer to the prescribed treat ratio.
Did you clean the MAF sensor with a non-residual product, designed just for cleaning the MAF sensor & kept it squeaky clean on re-installation??? If you found it was dirty, did you look upstream to find & correct the unfiltered air leak, so it won't get dirty again????
Using a 180 deg thermostat isn't recommended. Our lubricants, computer, engine, emissions system aren't calibrated to operate at that temperature, so our mpg won't be as good as the engine will run richer, again loading the combustion chamber with deposits your trying to remove & the cat converter is operating hotter having to process the unburned fuel, not a desirable scenario.
The reason I asked in my first post if you had any trouble codes is that your flex fuel 3.0L % ethanol fuel sensor is known to act out & cause fuel trim problems. This engine also has special heat range spark plugs specified, so that's why I mentioned checking to make sure it has the specified heat range plugs.
More thoughts for consideration, let us know how your spark knock trouble shoot goes.

 

Gotcha, Understood, logical.

Where is the ethanol fuel sensor? and can it be tested or must I replace it?

PO Did, I'm pretty sure replace the spark plugs, I'm gonna pull 1 to see if its the right spec, and gapped correctly........

My engine runs so very well, very smooth, no other issues other than the spark knock.

 

Good idea to check the spark plugs the previous owner installed, as too hot a plug can cause pre-ignition.
That along with using premium fuel thats tougher to ignite & get going, can result in an incomplete fuel burn before the exhaust valve opens, so those deposits on a hot plug can cause ping when we put the engine under load/more heat, like climbing a hill, or when we go at throttle up to pass.
So if you don't have any pending, or set trouble code clues, we have to do a drill down trouble shoot to make sure all of the basics are right first, before suspecting deposits as the only cause.
A number of things like a lean air/fuel ratio from vacuum leaks from disconnected, loose fitting, dry rotted vacuum lines, intake manifold gaskets, stuck open PCV valve (as its down stream of & not monitored by the MAF sensor) thus if its sticking, or stuck open, is an uncalculated for vacuum leak, wrong heat range spark plugs, out of spec octane fuel, overheated engine, or one that has poor coolant circulation around the affected cylinder can cause it to run hot & not indicate so on the temp gauge, or computer engine coolant temp sensor, low fuel pressure causing a lean fuel injector squirt, lazy O2 sensors & On & on the basics go!!!!
If your getting relief from the ping when using premium but otherwise its running good & no pending, or set trouble codes stored, & all basics check out, it suggests to look for deposits as the root cause. Keep us posted on what you find.

 

I don't remember where the under hood the fuel sensor is located on the flex fuel 3.0L, but a forum search will turn up its location & yes it can be tested & a search will turn up how to do it if necessary but that's not necessary if you don't have a trouble code for it.


So again, scan the computer for pending, or set codes & post All code number clues found. If no codes found, begin checking the basics.

 

I cleaned the MAF with MAF cleaner, it didn't look dirty to me at all.
AFIK, I have no codes stored, I've never seen the check engine light come on since purchase in October.
I replaced the PCV valve with a brand new Motorcraft unit as part of maintenance.
I have checked vacuum lines for rot and breakage.
This morning I'm going to pull a plug and see what I've got......
I read on another Ranger forum that after '01 they didn't use an octane sensor on these......I also read that IF one is present that its near the fuel filter......

 

OK, good feedback. Your pecking away at it in the right manner. When you filled up with premium, did the ping stop???? If so, maybe all that puppy needs is a good "Italian Tune Up", so, since adding the Seafoam to the premium fuel have you taken it out for a good high rpm highway run????
EDIT: Have the computer scanned for pending, or set trouble codes & post All code number clues. Most autoparts stores will do it at no cost if the CEL is lit, some will do it even though it isn't lit if we're having problems. If you need to turn the CEL on, just leave the gas cap loose on the drive over to the store & that'll turn it on.
Does the CEL light up for its self check at KOEO, before you start the engine????

 

When you finally find the answer to your highway ping problem, maybe consider using a Top Tier fuel that has an up scale ad pack to all grades. Here is a link to their current retail providers. Top Tier Gasoline

 

Wooops, my oldy moldy mind forgot we were talking about an 03 flex fuel, so your right about it not having the ethanol sensor, as it appears Ford mapped the O2 sensors & programmed the computer to sense the amount of O2 in the exhaust & have the computer adjust fuel injector squirt time longer to compensate/enrich the air/fuel ratio to adjust for the extra O2 in higher % ethanol fuels.
SO, also put the O2 sensors on your suspect list if they have over 75K miles on them, as they get lazy & slow to react when they get old, sorta like me!!!! lol
If the premium fuel, Seafoam & high rpm tune up runs don't have a positive effect, hook up your ELM327 scantool & pair it with your viewing device running FORScan, or the program of your choice, to monitor fuel trim & O2 sensor response time & range, to see how your upstream/before cat converter O2 sensors are doing & let us know what you find.

 

UPDATE: Filled up with BP 87 octane gas yesterday, I've already driven almost 100 miles on this tank, and even considering I have a sinus infection and can't hear out of my right ear right now I cannot hear any spark knock.

I rarely use lower tier gasoline in any of our vehicles, I had been big on Sunoco, but THEY aren't a top tier fuel, so I won't be using THAT anymore.

I also pulled a plug (have a strong suspicion that the PO had JUST replaced the plugs)(AND wires) before I bought it in October, there were new looking Autolite AGSF32FM Platinum plugs in it!

According to MY '03 owners manual the FF 3.0 calls for AGSF22PP, which is a DOUBLE PLATINUM plug.....thinking its ONE full heat range COLDER than the AGSF32FM plug.

I went to our new O'Riley's and they cross referenced the AGSF22PP to a current Autolite APP103......THIS also IS a DOUBLE PLATINUM plug.

I'm going to gap them (sticker says .42-.46)......shall I gap them tight at .42 or just go in the middle at .44 or go "wide open" at .46??

I'm also going to disconnect the negative battery cable while I'm changing the plugs, then start the engine and follow Ford's recommendation that's in my manual to allow the computer to re-learn.

fingers crossed!!

 

Good idea to install the specified heat range spark plugs. As spark gap is always opening up with time, I gap All my vehicles that are using the specified newer design fine wire iridium enhanced center electrode, with platinum pad sidewire plugs to the Lower/Tighter specified spark gap, using a Wire gauge.
Be careful to sneak up on the gap you want, so as not to force the gauge through too tight a gap & damage the sidewire platinum pad, or the finewire center electrode.

These iridium enhanced plugs spark gap will stay in spec longer in our waste spark ignition, that works our plugs Twice as hard, firing them on Every crankshaft rotation.
Once on the power stroke & again on the exhaust stroke (waste spark), as the iridium enhanced center electrode tolerates higher heat better than the non platinum/nickel electrode copper core, or single, or double platinum plugs.
The newer design Finewire center electrode plug is easier to fire, also has a hotter spark kernel & that along with a tighter spark gap, will help get us going quicker, especially on those cold winter morning starts when the battery voltage is lowest trying to crank a cold engine, run the fuel pump & make a hot spark to get us started.
I've noticed quicker year round starts since changing all my family vehicles over to the finewire design plugs, so as you can tell, they get a thumbs up from me.
Keep us posted on how it goes.

 

Thought I'd stop back at this thread and update:

I FINALLY installed the CORRECT Autolite APP103 Double Platinum plugs!

I have been running Chevron and BP regular 87 octane fuel for the last several tanks.

I unhooked the negative battery cable while I changed the plugs then re-connected it and started the engine and let it run for about 20 minutes to get to operating temp, then turned on the a/c and let it run for another 20 minutes-(This is per the owners manual)
Results are very promising so far, I have VERY VERY LITTLE spark knock now, really not enough to talk about...but it IS there.
I AM going to swap the Thermostat with a 180* now.........I AM in Florida and lets face it-its summertime now!
I was advised by a top notch mechanic at an a/c shop that it was generally safe to go to a 180* but no lower.
It runs so well, VERY smooth, can't tell its running most of the time!