I have a 98 F250LD Lariat. Today it developed a miss. It will idle ok, but when it labors it will sputter pretty good. NO check engine lights, ran the code reader to make sure. I individually disconnected all of the injectors and coil packs. I replaced all spark plugs about 6k miles ago, running fine ever since. It started its miss on the second trip of today. Drove it home, but definitely has a miss.

What I need: either point me in the direction of a good diagnostic scanner that will do cylinder ignition and fuel drop tests, or modern equivalent to see which piece is not running the way it should.

or

how do i diagnose this problem??

I thought it was #4 injector playing with the plug, but now that doesn't seem to make much difference, and when I pull the plug it definitely runs rougher.

I am out of work, and I don't know how I am gonna fix this anyway (here comes the Visa.. but I cannot afford to throw parts at it like I normally do.

I also have a 97 250 7.3 power stroke, so if i need a diagnostic tool, one that would also work well for that would be great!!

The code scanner I have now is pretty cheap, and just reads codes, IM readiness and live data, not much more.


Any help would be super great!!!

Thanks

I am starting to remember why I swore never to buy a newer truck than 96......

 

Just some suggestions you could do without spending any money... check the air filter... spray it off with compressed air. MAF sensor could be fouled, but unlikely... clean it with a can of electrical cleaner. Throttle body could be dirty... could take off the intake tubing and clean out around the butterfly. Some cheaper alternatives is run a can of seafoam through it. Could get a new fuel filter to see if that may be the problem. Fuel filters are pretty cheap since you are on a budget. Those are the basics that i know of, as far as you checking the plugs COP's and injectors, you did everything right to check them.

 

Or you could also check your PCV valve and tube and make sure they have vacuum. Check all your other hoses as well and make sure you dont have a vacuum leak elsewear. Also you can check your EGR valve and clean it up, its next to your throttle body on the left hand side looking at the engine. These are just some of the things i can think of that are easy to clean or cheap to replace. Hope it helps.

 

I don't think an inexpensive scanner will help, also you didn't state which engine you have. Being a F250LD I'm guessing 5.4, since you stated a miss the odd's are you have a coil ( C.O.P. ) going out ... make sure the CEL bulb is working and just drive the thing till it gives you a code.

 

Well, thanks all for responding, first off.

Yes, sorry 5.4 with coil packs. I really feel that it is either a coil pack or injector, it came on all of a sudden, from running perfectly. Driving till I get a code is not an option, it runs too rough for that. I guess at this point if there are no ohm meter diagnostics I can use, what is a good diagnostic tool for me. I do have a lap top, if that helps. I would like to not spend over 450, if possible. Does anybody have any more ideas??? I will check those other things.

MAF seems to be working by live data feed, it has a fresh K&N air filter, fuel flow seems good by live data.

 

Well you said you changed the plugs not long ago, I'm hoping you used Motorcraft ( second choice Autolite ) I was out of work for a year so I understand being short on cash, if you also feel it's a coil can you afford one? If you buy one coil ( C.O.P. ) and move it from one cylinder to the next you might get lucky? Also be aware that above the #4 cylinder there's a heater hose that may be dripping fluid on the coil below.
Best of luck to you.

 

I used Bosch "platinum 4" plugs in it. I moved the coil pack from #4 to #1 for easier access, it was dry, and did not seem to be the problem. Why only motorcraft plugs???? I REALLY don't want to do plugs again, till it gets an engine swap (soon at 175k). I suppose I need to get something to fix it. And it wouldn't be that bad having an extra coil pack if that is not the problem. For some reason, I still feel its an injector. Call it a feeling. I have actually never had an injector fail on me (All my previous trucks ran propane, didn't use fuel injectors), so diagnosing a half bad injector is a little new to me. My dads crown vic had the same problem a few years ago (99 4.6 with coil packs) and it turned out to be an injector, but he ended up bringing it in. I don't know, I need to become more educated on this new technology in these new trucks. When I got the truck last fall, I used Lucas oil fuel injector cleaner for 2 bottles, and not for a while since I ran out. Any way there could be a problem there, or maybe I need it again??

Edit: platinum 2 plugs

 

Ive actually heard that Bosch are not good plugs to use in these trucks, because they dont last long... pull the injector plugs individually and if it runs worse when you unplug one, then thats it. Same with the COP's. Though you said you already tried this, i would try again and see if there is any difference in the way it runs.

 

Hmmm, never heard about that about the spark plugs. Not cool. I will pull one and see how it looks. I will try swapping coils tomorrow, one at a time and see what I get.

 

UPDATE:

In case anyone was interested for future reference, It was the #4 coil pack. I wish the computer would tell you one is not firing right.

 

Hey Darkmage55, where did you hear that Bosch plugs were not good? Ironically when I order my '98 F250LD Lariat SC new, it came with Bosch Platinum's from the factory. I just replaced then at 150,000 miles and they still looked good. I had a miss that was a bad COP not a plug, so I'd have to say from personal experience that a Bosch plug is as good or better as any other.

 

That # 4 cop is a stinker for sure. Unless the engine is missing really bad for a long time from a cop they don't always throw a code. For future reference the way I usually check the cop . Because a slight fowl is hard to pick up at idle. Let someone sit in the truck. Put all the brakes on and put the truck in reverse and bring the rpms up to about 1800 or so and then disconnect the cops and listen for a change. It will be clearer under load.

 

Here is some info to support your finding of the faulty coil.
The issue you had was a coil with "shorted" turns.
The PCM will not set a code because the type of fault is not a 'hard' fault.
The fault shows up as intermitant missfire under certain 'light load' driving conditions.
Additionally, the brake test method won't pick it out either because the same set of conditions that cause the 'type' of missfire cannot be set up doing a low rpm brake load test.

 

99 F250 LD 4x4 w 5.4l. When my truck started missing like that. I simply
opened the throttle body up slightly and started unplugging cops 1 at a time. When I got to # 4 I could tell it was the problem because on all the others I could detect a change in the rpms and how smooth the motor ran. So I know it worked at least once.

 

I think with that type of miss that it was having, swapping coil packs was the only way to find it. Like was said, not completely missing on that coil, just a weak spark, and thus throwing no codes. Could have even been a weak spring in the coil, not getting good contact with the spark plug. At least now I am familiar with that problem/solution. The more you know, the less you swear.