2009 6-speed

Hey Everyone, new to the site and need some help.

I just bought my 2009 F150 with the 4.6L 3v about 3 months ago and I have an issue that I cannot solve. Motor has around 140,xxx miles on it. Here it is: Under light acceleration, from about 30-55mph the motor is very low on rpms. When I go to accelerate slightly (say someone in front turns and I want to get back to cruising speed) the truck rpms will drop slightly and jerk couple of times(like a cylinder misfire). The only way I can get out of it is if I give it more throttle and it downshifts. It is extremely frustrating since I feel like I am always driving at these speeds! I don't really have money to throw at different parts of the truck that won't fix the problem so that's where you guys come in!

I just replaced all 8 coil on plugs with Motorcraft coils. Did not replace the plugs themselves.

Any help would be awesome! If i left anything off, let me know. Thanks!

SCORGE

May be time for spark plugs.

joe mcmillan

Should be some codes. Even if you havn't seen a wrench light, check for codes.
No code reader - go to your local parts store and they can read.

techrep

iTrader: (1)

I would of done the plugs first if I did not have the money to toss parts at it... 8 motorcraft COP's is a nice chunk of change not to fix a misfire.

2009 6-speed

I did go to auto parts store. No codes at all. Only happens in that range but it is consistent.

Martian

Agreed with the others - change your plugs. Also clean your throttle body.

v8_STX

I'd also say your next step is the plugs. Be sure they're gapped properly before you put them in. If the local shop has a compression tester, now is a good time to look at that.

The other places I'd look would be the fuel filter and fuel pump (and maybe the relay for that), and anything else in the path (air filters, throttle, throttle cable, so on). 140k is enough for the throttle cable to get a bit gummy, so that might need cleaning, too.

Jamesexcavating

is it a jerking problem or a shudder? my 2010 4.6 3 v has the trans shudder it the same MPH range.

techrep

iTrader: (1)

Is there a throttle cable on a 4.6 ?

2009 6-speed

I would say it was jerking. If I keep the throttle the same during it, it will continue to happen. It only stops if I let off throttle or give it more. I will look at fuel filter next. It is just weird because it is only during those ranges at little throttle. Never have an issue otherwise