Hi new here and am really impressed with what I am finding here, looking forward to being a regular!


I just bought a mint 1999 F250 Triton V10 (5 speed) and now less than a month after getting it I have a low speed miss I just can't seem to solve. First the problem, during acceleration all seems fine and it runs great but at low speed and below 1800 RPM or so it misses noticeably and if I depress the throttle without down shifting to bring the RPM up to at least 2000 it will shudder quite badly. The only code I am getting is for "random multiple cylinder misfire detected". So far I have checked the catalytic converter, replaced the O2 sensors, replaced the plugs, Checked the EGR and DPFE, checked the TPS, checked the ignition coils (only did resistance checks with DVOM) determined there are no vacuum leaks and checked the fuel pressure. I also replaced the fuel and air filters and cleaned/tested the MAF. At this point I simply don't know what else to do and I thought I had covered about everything so I am starting to think maybe one or more of my checks was not as thorough as I thought. How else should I check the coils besides the resistance checks?

 

Just ran across this thread...saw no answers, but wondered if you figured it out and what it was. I have a '99 F350 V10 with the same issue...threw a P300, and a P0174 for a bit (lean condition bank two). I wonder if I have a band tank of gas which is causing a random lean-out misfire across the board, and got that P0174 the once due to perhaps crud or water cutting out injector(s) on bank 2.

Anyway, if you got it fixed, let me know what you did.


Thanks!

 

Yes I fixed it and I learned a lot along the way! First, the problem turned out to be coil packs, not just one but two at the same time. Next I have found this is a VERY common problem with this ignition system and can be very hard to diagnose. When I did the shop manual tests on these things they checked out good showing to be well within proper resistance range and I even went so far as to rig up a bench tester and the coils would seem to be firing OK. When a friend of mine informed me that the rubber boots from the coil to the plug is a common problem I replaced all of them at a cost of about $55 and sure enough a small improvement did result but the problem was still there to a very noticeable degree. Out of frustration I bought one coil pack and started replacing one cylinder at a time in this order-

Place the new coil pack on No. 1 then test drive, if no improvement replace the No. 1 cylinder coil with the original and move the new one to No. two, and so on.


I did it this way until I came to No. 5 at which time there was a major improvement but unfortunately not 100%, it was a big help however and convinced me I was on the right track. I kept thinking that there just couldn't be two packs bad at the same time could there? Well I went back to the auto parts, bought another coil pack and started the process again where I had left off. When I replaced No. 7 my problem was finally solved! Like I said this can be a very difficult (and expensive!) problem to diagnose because normal test procedures often give false results and even when testing good the coil packs can fail under load. A bad boot can cause the same problem as the bad coil but just like plug wires on a conventional system these need to be replaced periodically so you might want to start there first, a new boot is included with a new coil pack or they are available separately ($4.99 each at Auto Zone) . If changing the boots does not help, or only helps partially, then I would suggest doing as I did and buy a new coil pack to check the cylinders one at a time. Like I said earlier one of the things I discovered is that the problem I had is very common on these things!

I really hope this is of some help because I know from experience just how frustrating this problem can be.

 

Thanks for the reply. I am trying hard not to replace coils yet, but I'll look at doing boots. I had a lean condition code only once, and now just every once in a while I have that random misfire. I haven't figured out if a coil can set that off without IDing the cylinder, but I did put a can of seafoam in the tank and it seemed to help a lot for a bit...my current thinking is I have a tank of bad gas...a full tank of bad gas, sigh...so once I run that tank through, I will be changing the filter, and seeing if I can test the fuel pump. Easy stuff first. But I understand the frustration of anyone working on these Fords...good mechanical bits, but dodgy electronics. Eh, even these days Bosch has issues, and thankfully we aren't working with Lucas or Marelli, which would make just want to blow the truck up.

If I find a magic "that fixed it!", I'll post it asap.

Thanks again for the reply!

 

I have a 1999 F250 Super Duty that misfires But only when its cold once the temperature comes up the truck begins to run better if I start it and let it warm up for a half an hour or so and I dont have any troubles,. I have replaced the Spark Plugs (Motorcraft Platinum) and replaced the coils and still the same problem P300 also have seen 302 and 304 Now I do know the battery isn't in best contition cause when I changed the plugs the batter went dead while running the radio,.. Could this be the problem? why cant we go back to the old days when there wasn't so may wires, hoses and relays? this technology is better?? really??? did my computer get a virus??? really??

 

I have been learning a lot about these truck but still having problems,. capeferrelometal if your truck is running lean its due to a vacuum leak check large hose connecting to PCV this is a rubber hose connected to the intake under the throttle body this is common to replacement,..

 

Hey Fix,

Problem turned out to be a combination of things. The initial misfire was simply a corroded spring on #8 cylinder. I replaced all the boots. The lean issues turn out to have been a combination of a bad MAF and loose connectors on several injectors. Just for good measure I replaced the O2 sensors in the downpipes, and put in a new FPR and fuel filter. The sensor on Bank 2 sure showed a poor running condition. I changed the plugs, tied down the injector clips and put in the new MAF and the truck is running better than it ever has. I do need a scanner that can give me live data including fuel trim, but the problem has been solved and I am happy.

 

I have to work on Triton fords every so often and the coil ignition systems can cause problems that are very hard to detect since the computer might not pick up the misfiring.

 

I am finding this out,. so far I replaced the coils then put all the original ones back on guess what,.Most of my problems are gone,.. now I am weedeing out the ones that are misfiring,.. I love my Ford but talk about bitchy,..lol.. I think if they are gonna have this problem the should just name as such The New Ford "Misfire",..

I would like to say Thanks to everyone that post problems and fixes this has been more help that the dealer,..

 

The most confusing thing about these darn coil packs is that they usually check good using traditional test methods such as a resistance check with an ohm meter. I even rigged up a bench tester using a condenser (capacitor) and a switch to simulate a set of points and the "bad" coils seem to fire just fine, put them under a load in the engine and they fail! Seems that the only ($)olution is to buy a new coil or coils and replace them one at a time until the offender is located. I spoke with a mechanic at a local Ford shop and he told me that is how they do it, of course it is easy and cheap for them!