I just recently changed out several parts on my 1997 4.6L F150 (spark plugs, EGR solenoid, DPFE sensor, and fuel filter). I also cleaned out the throttle body a bit, but my truck is still running rough at idle and speeds over 40 mph.

I don't have a check engine light on or anything, but it runs as if there is a misfire going on. Does anyone have any idea what may be causing this?

 

Have you checked your MAF sensor?

 

Didn't think about that. I'll check it out and see if it needs cleaning. Thanks!

 

Coils

 

I just changed the ignition coil packs last week too. Forgot to mention that.

 

Defiantly coils. Had the same thing happen to me last year.

 

Before, the CEL was on and giving me a P0401 code (which is why I replaced the DPFE sensor). After replacing the sensor, the light went away but the engine still runs rough. Do you still think the coils could be the problem?

 

PO401 has nothing to do with the way she runs...just so you know. A PO402 might!

Sounds to me like it may be a converter. Do you have any power over 45 mph ? Like say for passing ?

 

What kind of spark plugs did you use ?

 

I used platinum spark plugs. Can't remember the exact brand. I just checked the MAF sensor and it doesn't appear to be fouled up or anything. I still have power over 45 mph, but it feels like the engine starts shuddering when it gets to those speeds. I'm about to have the oil and air filter changed as well since it's about that time, but I just want this thing to run smoothly.