Hi guys I have a 2004 Ford F150 FX4 supercrew with 81k. I recently got a new battery put in my truck a month ago but when I drive the truck for about 10 mins when I slow down and the truck gets below 1000 rpms it will start shaking and it sounds like a violent engine knock and sometimes it just completely shuts off especially when turning. I took it to my ford dealership to have the check engine light diagnostically tested and ford said there were no codes showing anything wrong and that it runs fine...and it absolutely doesn't...any ideas on what the issue could be or a solution?

 

ttt

 

have you already went thru the basics? clean MAF, TPMS, change air filter, change fuel filter? when was the last time you changed the spark plugs? and coils?

 

Did the check engine light turn on at all? If the light was on even for a second there will be codes stored in the history. Sounds like you have a misfire/timing issue, and the knocking you hear is predetenation because the fuel isnt being burnt correctly. Something isnt working right.

 

spark plugs are still original and i have a new air filter but old fuel filter...someone said it might be the throttle body? Also the check engine light has been going on and off but has been on fer the last few weeks. when i took it to ford it said there was no codes stored so they couldnt tell me why the check engine light went on

 

suzukirider- it sounds like your right because i have to give it gas to keep it above 1000 rpms or it will stall

 

Could be a cam phaser dropping off and retarding the timing. That can either be caused by a bad phaser or low oil pressure.

edit: That is incorrect information I gave. But what it actually could be is a cam phaser solenoid stuck open causing retarded timing at idle. At idle the spring holds the phaser to the advanced position and then the solenoid is duty cycled to apply oil pressure to retard the timing. If a solenoid sticks the oil pressure keeps the timing retarded which will make it run rough at idle. To test unplug the cap phaser solenoids to see if it clears up.

 

im not sure what the cam phaser solenoids are is it something I can easily do?

 

You have a miss. That's why the check engine light is intermittent. Don't worry about cam phasers, check the more likely stuff first.

Like others said check/clean: throttle body, MAF ssensor, and inspect the coil packs. Check for vacuum leaks. If all of these are good then I'd change the plugs.

With an intermittent miss like you have, my money is on a bad coil pack.

Only after checking all of the above would I even consider the cam phasers. Cam phasers are known for creating noise but I haven't heard of a bad one contributing to a miss/stall condition, especially at your mileage.

 

Yeah the solenoid connectors are right on the top front of the valve covers. Have you ruled out the throttle body they're known to go bad? Also running lean could cause your problem, if your check engine light was on you absolutely have a code in history unless you had autozone or someone clear it. The odds of a throttle body being your problem is a lot better than cam phasers, I probably shouldn't have even mentioned it.

It could be a miss like jhight said but usually you would idle fine and miss under a load and at higher rpms or miss all the time. Not the way it is happening. And yeah I shouldn't have mentioned phasers, forget it happened. For some reason I was thinking The other stuff was ruled out already.