2004 f150 4.6lt Triton

Asked by Jul 20, 2017 at 11:38 AM about the 2004 Ford F-150 XLT Ext. Cab

Question type: Maintenance & Repair

My truck was running fine. Then coil pack
went out.. i have replaced all of them. Put
new plugs in. New fuel filter. Complete oil
change. Fitee breather filter everything. Even
a fuel rail cleaning. Still when its cold it runs
great. But after running for a while truck
shakes really bad. At idle shakes really bad.
Wont accelerate quickly power of motor real
low. Between 1500 &200 rpm bad shakes.
Over 200 rpm shaking stops but truck has
no power.. when warmed up sounds like a
diesel. Spent a grand now. Just got a new
brain box but still cant read codes. Please
help.

2 Answers

25

Sounds like your cylinders are misfiring. Make sure that the plugs you installed are to spec, meaning make sure they were gapped correctly before installation and that the plugs were made for that particular engine. If coil packs were replaced, those should be fine.. You claim to have cleaned the fuel rails but you could have a failing fuel injector. For starters, I'd get the OBD-II working to check out the codes and then just google for code interpretations. Hope this helps.

20,410

Since you spent all the cash I suggest you spend another hundred bucks and have a mechanic do a live data analysis on the engine while it is idling. It does sound like a misfire in one or more cylinders, but what is causing the misfire is the key. It could be bad injector(s) or loss of compression in one or more cylinder. The live data will indicate which cylinders are misfiring narrowing the cause of the problem significantly.

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