Spark Knock noise when passing

Under heavy throttle and when passing other cars I notice a spark knocking sound.. Would not notice if radio is on and even AC for it is very hard too pick up unless you know what you are hearing. Has anyone notice this problem.? I am not worried about it yet but would like to know if this is a common problem with the 4.2.

Well the noise I found out is the motor and I guess is normal for the 4.2. i heard a F150 when reving the motor sounded the same. I think the 5w20 makes this sound more .. I am getting ready to switch to mobil 5w30 full synthetic. I was just waiting for the miles to get a little higher. I think this will help with that noise.. It has in other cars and vans I use it in.. Tends to make the engine run smoother,to me any way.. Ill post back with results later.

I have V6 4.2 ltr F-150. Can't say as I have heard that noise. How do you like you Freestar? I have a 98 Windstar that is ready to be put out to pasture and was thinking of buying a 04 or 05 Freestar. Are there any big issues I should be aware of. By the lack of threads here they seem to be alright.

I have V6 4.2 ltr F-150. Can't say as I have heard that noise. How do you like you Freestar? I have a 98 Windstar that is ready to be put out to pasture and was thinking of buying a 04 or 05 Freestar. Are there any big issues I should be aware of. By the lack of threads here they seem to be alright.
I have a 2006 freestar and a 2001 Windstar. I like them both fine.. But you dont really hear that spark knock noise unless you really try to hear it. Maybe lower grade gas causing it don't know really. But the Freestar is fine no major issue as of yet just got to keep the trans fluid changed.

My 2006 also knocks under heavy load - quick passing on highway. I have tried high octane fuel and fuel system cleaners. I think this just might be the way it is.....

My 2006 also knocks under heavy load - quick passing on highway. I have tried high octane fuel and fuel system cleaners. I think this just might be the way it is.....
Just read the owners guide. It said not to run High octane it could cause this problem.. LOL. maybe someone ran it before I got it.. Almost like they know its going to spark knock a little.. They say use 87 only reg unleaded fuel. Just thought I would update... Gary

Update on spark knock... Van spark knocks is louder. Taking to dealer to see what they think.. If any of you have this issue you may want to complain or keep an ear out for the noise. They may have to update the timing on the ECM.Will see what the dealer comes up with. Its still under warranty..

Hey Gary, I bought a 2005 Freestar limited. 20K miles. Getting ready to make the first payment on it :banghead: . Seems like a good runner so far although I haven't driven it a hundred miles yet. I haven't noticed any odd noises yet. Let us know what the results of the dealership are.

UPDATE!!! Just drop the van at the dealer today.. They seem very aware of this problem. I know on other Fords they have re flashed the ECU so will see what happens..He Asked what type of gas I run and I said I know where you going with this. With the high price of gas I stay with 87.. Im not going to pay for premium when the owners guide say run 87..In other words if I were to have run premium he was going to say it was my fault. The Owners guide tells you not to run premium.. WOW thanks Ford.. I use to run a little premium gas in older cars to see if it would help on spark knock..To see if the distributor may need replacing if I could not get it to time right..Most of the time spark knock is caused by improper detonation in the cylinders over time this is not good..Most of the issue I have found to be engineering.. Not enough of one or more gas,spark and timing of the detonation. On the older jeeps upgrading to HEI distributor solved this problem. Means that in that case, not enough spark..
So will see what happens..

Just got back from the dealer they updated the CPU with new timing setup.
Still hear it a little not as bad as before. He gave me a print out of the octane rating to use only 87. I laughed and said with the gas prices they way they are I would not even think of running premium..Even if I had a sports car.. He said from the factory they lean these things out for gas mileage. I said they need to fatten it out a little then..If you do have this problem I advise you to get it checked out if you can hear it over the AC or heat at full blast then its bad and needs to be corrected..It will damage the engine if left unchecked.So the light spark knock sound under engine load is acceptable.Other than that its not..They have not issued a TSB update as of yet but I am sure it won't be long.. If its not under warranty it will run at my local dealer about 94.00 bucks. I will try federal guide lines for emission which covers any car,truck or van for 8 years or 80,000 miles..If spark knock is classified as that which may not be...Hope this helps.Gary

Took a trip to the Beach this weekend and after the so called update to pcm notice this thing spark knocks worse when merging on to a hwy. Thought the darn thing was going to come apart.. Cruising you don't notice it but when putting the foot down its bad.. Back to dealer it goes..

[QUOTE=garync1]Took a trip to the Beach this weekend and after the so called update to pcm notice this thing spark knocks worse when merging on to a hwy. Thought the darn thing was going to come apart.. Cruising you don't notice it but when putting the foot down its bad.. Back to dealer it goes..[/QUOT


Took back to dealer yesterday and they tighten the AC accumulator and the Air filter box and Rechecked PCM timing and All seems well for now..