Alright, I really need some advice and from what I have read this board is the place to be !! I have read several posts on the misfire issue and tried every suggestion I could find with no luck. I have a 97 F150 ORP with 4.6L engine, 177,000 miles. This truck has been mine since new and has never NOT ONCE failed me until this last July. I was headed home from a camping trip when all the sudden the whole truck started to buck and shake wildly while the check engine light started flashing. I know the flashing CEL means misfire so I checked all the wires with no luck. I limped the truck home with no power and since then we have been trying to figure out the problem. I have had it into ford 2x for diagnostics but they cannot seem to pinpoint the problem without me leaving it there for a day or 2 @ 98.00/per hour. I just don't have 4-600.00 that they think it will take to find the issue so I am turning to the board to see if you can help me. I have done the following: New 9mm Ford Racing Wires, New plugs, Checked EGR, New Crank position sensor, new cam position sensor, new IAC, Replaced BOTH coils with HP Coils new fuel filter and fuel pump. Through all the checks and new parts there have been some improvements to the performance but no matter what I still have the misfire under load. Let me explain the problem a little better. If my wife was driving the truck she would think nothing is wrong because this problem only really shows up on steep hills or at near WOT, or in OD. Anytime the engine is "lugging" a bit I get the flashing CEL and it stutters like crazy, from a stop if I stomp on it I have lots of power UNTIL I get to second gear, then it lugs and misfires again until the RMPS get up there. If you drive with a soft foot it will get up to 70 without really feeling the issue (only a couple misfires) however any attempt to open it up seems to result in a misfire. I appreciate any help anyone can give !!! THANKS !

 

im having kinda the same problem, with the misfiring and stuff..

 

It is the worst problem I have ever had, not because it is noticable just because noone seems to be able to find the problem.... This board is my last attempt to get it fixed... if this doesnt work I may just drop a lightning engine and PCM into it ;-)

 

i changed my wires last night.. and now im getting a vacuuming sound that i cant figure out, and im going to have my plugs changed today hopefully cause i cant get to them myself....

 

Tote it down to Autozone and find out what codes are stored in it and we can go from there.

 

My 97 does same thing codes read mis fire plug 4 or 7 have changed out wires, plugs and packs but doesn't help and Ford doesn't know whats the matter either, I think it is a vacuum prob but not sure. Starts after driving for five minutes and sometimes goes away after on interstate for an hour. It returns next day however, and some days it won't do it at all, worst under load though.

 

did the 2 ford dealers hook it up and check the injector patterns or did they just do a code scan and have you throw parts at it?

if you haven't already done so do a search here on missfire. It seems in most cases chenging the plugs and wires have no affect it seems the way they were installed is more important.

You may simply need a carbon depletion process. You said that you checked the EGR. Did you check the whole system or just they valve? 4.6's are famous for glogging up. However I don't think that is your problem because you are having a miss and not a ping.

good luck.

 

They said they couldn't find anything, the service writer said one of the mech. worked on it for five hours and still couldn't find a reason. He said the computer only told him plug 7 and 4 (seperate trips) were miss firing, however he did not replace the wire on number seven the second time because I marked the wires before I went in and they were still marked when I came out. I changed the wires and plugs myself ( could have done that anyway but thought it might have been a vacuum leak that I couldn't figure out. I also changed out the coil packs myself and that seemed to help a little for a little while but prob. came back after a week or so. So far Ford's finest haven't been able to fix it.

 

I forgot to mention that I have brand new ford 19lb injectors in the truck. Also I have cleaned the entire intake housing, removed the elbow and cleaned the EGR ports. No EGR codes are being thrown, OBDII only shows a random missfire, usually #7 but sometimes #4 &6. Could the timing chain have slipped on one side ??? HELP