AvidAjx

Hello late model owners!

I recently purchased an 05 f 150 fx4 with 140k miles as a project truck/daily driver and seem to be in a never ending battle with the engine.

I'll do my best to keep this post as organized as I can because frankly there's quite a lot going on..

Problem number 1: Ignition/Start Up- After purchasing the truck I immediately noticed it took a lot long to turn over than any other vehicle I've driven. I was advised to change the spark plugs and the fuel injector which I did. I noticed a slight difference for about a week but quickly found myself with the same exact issue. I find myself having the prime the vehicle two or three times before I actually turn the key forward and it still takes 10-15 seconds.

Problem number 2: (ties in with problem number 1) Rough Idle- When I first turn the truck the engine shakes something fierce while the RPM fluctuates between 500-1000. From time to time the RPM jumps to 1200-1300 which makes this issue worse. I also experience the same shaking when I'm at a red light or a stop sign.
Before my trusted mechanic went out of business he retrieved a few misfire codes from cylinders 2 and 4 and said that was the source of the problem but unfortunately I have yet to find a mechanic who I can trust to make that same judgement call.

Problem number 3: Lag in throttle response-
I frequently experience this issue in the passing lane on the expressway. Aside from the natural sluggish behavior the truck produces- I often find myself pressing the gas peddle to maneuver around someone or when I'm climbing a hill only to feel like the truck is dying out.. I literally get ZERO response until seconds later.

Problem number 4: Knocking in the rear of truck- I'm hoping this issue isn't more serious than it seems.. When I'm first putting the truck in gear or accelerating from a stop something in the back end of the truck knocks before it starts to move. It's done this since I've purchased the truck without fail.

Problem number 5: "Limp Mode"- I'm still trying to find what specifically causes this issue but like many have experienced my truck goes into limp mode from time to time. It's happened to me twice in the past month both at the most unfortunate of times.. The first time I was sitting at a railroad crossing with the truck in drive from roughly 5 minutes. I put the truck in park and proceeded to wait another 5-10 minutes. When the train passed and I put the truck in drive the yellow wrench light came on, my steering wheel locked up and the truck proceeded to roll forward about 10-15ft which luckily was just enough to get over the tracks. From what research I could find the three main issues that cause this problem are linked to either the air filter (which was changed) the fuel injector (which was also replaced) or the throttle body (which was cleaned about a month ago). I've already ordered a new cold air intake system from SB and an 80mm throttle body from BBK which I hope will solve this issue.

So, as you can see.. I'm fighting an uphill battle here.. I've always wanted this exact truck since I was young. I'm willing to put how ever much I need to into it to getting in running condition. At the same time, I don't want to feel like a complete moron throwing parts at a truck that I may or may not actually need at the moment.

If there's any advice or solution any of you can provide to help me with any of the number of issues im having please do not hesitate.

Thanks!

screamineagle

First off, when you receive your "cold air" intake and TB. Send them back for a refund. What brand of plugs did you use? Might have a bad COP and or boots/springs. When you say you replaced fuel injector you mean you replaced only one or all 8? Before throwing any more parts at it I would check the fuel pressure. Also drop your spare tire and look at your FPDM. They typically corrode and cause all sorts of fuel delivery issues.

bbrad1775

Agree with all of this.

AvidAjx

Could you please explain further why I should send them back for a refund? As for the plugs I would have the check. I purchased the wrong plugs and had to have a mechanic instal what he had in his inventory. Which plugs would you recommend? Also, could you elaborate on how the COP / Boots/springs would cause these issues? I'll look into the FPDM this weekend. If it is corroded what would be the course of action to replace it? This is my first truck and I really don't know a whole lot about it.

screamineagle

The stock intake draws cold air from the fender well. Aftermarket intakes draw hot air from the engine compartment. Plugs and coils should be Motorcraft, other brands cause alot of problems with these modular engines. The FPDM will be obvious if its corroded, its not uncommon for them to crumble apart when removing. If yours hasnt been changed then its a safe bet it is shot. A new one can be sourced at your local parts store or you can save a few bucks and buy one online such as Amazon.

dom07

Problem 1: Daily driver and project truck. There can be only one. Never both. So, lets call it a project truck.

First, get some Motorcraft plugs in it. If there are any non-Motorcraft coils, you'll be better off replacing them. Nothing but problems reported from other brands.

Replace the FPDM if its corroded.

It's ok to use a dorman here.

Never throw aftermarket parts at basic problems. Intake tubes and throttle bodies are worthless, save your money. It was said -- get a refund.

It is worth putting a fuel filter on it too, cheap and easy. Then post back after all this, and lets see what remains.

Oh, and on the knocking, dont worry -- that's usually a simple matter of lubricating the slip yoke. It's very easy, leave that until you sort the other problems.

AvidAjx

I want to thank you and screaming eagle both for all of your help. It's crazy to think that a few guys on the ol interwebs can provide me with more answers than the mechanics im paying 40 an hour for lol! I plan on replacing the coils soon with the motorcraft brand next week. While I'm down there is there any way I can identify what brand plugs I have without pulling them out? I was told that these engines have a problem with the plugs snapping when you try to remove them.
I'll replace the fuel filter while I'm working on the FPDM. Again, thank you both for all of your help. I'll keep this thread updated. Please subscribe so I can follow up with you both.

Summers22

iTrader: (2)

Plugs have to be removed to tell the brand. They wont break if the mechanics just replaced them. One question that hasn't been asked is if you have the 5.4 or 4.6? As stated return the CAI and throttle body and invest in Motorcraft parts, your wallet will thank you in the long run. I bought 8 used Motorcraft coils that had 15K on them from ebay for $120 shipped. Things looked brand new (they were off a 2012 Mustang than had been supercharged).

joe mcmillan

After the plugs have been changed there is no more removal issue. The original plugs were of a 2 piece design. The replacements are not (normally). You must remove a plug to see what brand and number it is. Should be Motorcraft SP-515.

Summers22

iTrader: (2)

True, if he has the 5.4. This hasnt been clarified yet. If its the 5.4, the shaking and RPM fluctuating at start-up and limp mode issues suggest timing work needs done.