I have 1997 f150 with the 4.6 v8 it has 110,000 miles on it. I was on my way to work today and after driving about 5 miles my truck starts to shake and miss real bad. I was running about 55 mph. As a backed off the throttle the problem would start to be less noticable, but if I start to accelerate it would come back. It did this the rest of the way to work (about another 5 miles). It didn't seem to matter what speed I was going, it would happen pretty much at any speed as long as I was accelerating. The check engine light came on and would blink whenever the engine would miss and then stay solid when ever I calmed things down by backing off of the throttle. I replaced the plugs about a year ago but it has the original plug wires in it. Any help would be greatly appreciated.

 

Well, there could be a coupla things wrong but I hope nothing serious..... The wires themselves are certainly suspect.... Your occurance is exactly how a friend of mine found out about his bad wires.... it was kinda sudden.......
Bad fuel or a fuel filter is a second thing to look at also........

I've got 2 '97 F150s with 4.6 engines and both are still strong running although they have 170k and 183k respectively..... the 4.6 is a great engine and low maintenance but some things are a MUST.... like wires....

Good luck......

 

You DO have a couple of things going because of the CEL behavior.

Blinking CEL means you have miss. The steady CEL means something else. Get the codes read at autozone and post them here.

If I were to guess with your year and engine I would say something wrong with the EGR/DPFE and as mentioned before bad wires.

 

DonnyD,

Push each plug wire on. Most likely one has backed off a little and only missfires to the block when under load. This has happened a couple of times to me. It is common on the early engines with duel coils and plug wires. The flashing check engine light is one of the give aways.

After you push all plug wire back on if it stops then disconnect the battery to clear the check engine light.

 

Thats exactly how mine is running!

I limped it to Autozone last night and had my codes read. P303 Cylinder #3 misfire. Under load the truck would stumble and miss, when idling or revving in neutral, it was smooth. Tonight I will be pulling it apart to see whats the matter. My check engine light came on and stayed on though.

 

Well, I went to Autozone and it came back with a 308 error code. Which I was told is a misfire error code. There was a number of possiblities as far as what could be wrong (vacuum leak, bad spark plug, bad injector, bad plug wires etc..) I picked up some plug wires, I will install those and see how it goes and post back here with the results. Thanks for all the replies so far.

 

I installed the plug wires and that seems to have fixed the problem. Took it for a 5 mile test spin and it didn't miss once.

 

Good to hear sbailey,

I just spent 2 hrs trying to get mine running right. I changed the plugs, but my wires weren't in yet.

 

GREAT!

 

well my bad luck needs to end I have 93 f150 that has a been a problem from the time I bought it--it was missing bad like it was a v6 from idle to under acceleration- it was so bad I could not get the truck over 20 mph. so I spent the day under the hood--I made progress but still have a miss with a different issue.--I repaired 3 vacuum lines,new cap new rotor new plugs and wires-- that did not help so I cleaned the iac motor and pcv valve that seemed to lessen the miss so then I went to a local junk yard got a different distrubitor and here is the new issue the miss has 75 % better I can get the motor up to 4000 rpm and 40 mph now but still has a miss I did replace the coil thinking that might do it but no and the ignition module was tested and passed so im about ready to give up--what else can it be

 

Check plug wires to make certain there aren't any crossed.

Check fuel pressure and fuel quality. Old/stale fuel or a restricted fuel supply (filter/pump/lines) will cause the engine to run poorly.

Check distributor timing.

Check for restricted exhaust.

Check for restricted air supply (filter, etc).

Run KOER self tests including the cylinder balance tests.

See service manual for details of each.

 

You may want to run a compression test just to see that it isn't a mechanical problem.

 

Plenty of things it might be.

I see a lot of "parts replacing" but I don't see any evidence of any real diagnostic or troubleshooting work.