Hi all,
'00 5.4 4X4 Supercab w/33,000 miles, out of warrantee last march. Have had 2 coils & associated plugs replaced before, but this is different. It happens under light load in overdrive, disappears if I downshift. Intermittent; ran like a chevy all day yesterday, put the scanner on it today & drove 50 miles just fine. I had to drive slow (hard for me) on the return 50 mile trip to get it to misfire. It only has a pending code, caught during "capture" mode (while driving). No Check Engine Light, no codes at idle. Pending Code: PO300 Random / Multiple Cylinder Misfire Detected. Any ideas as to what might be causing it? I don't have a clue as to what's where on a distributorless system.
THANKS IN ADVANCE,

Dan

 

Random misfire can be electrical but it can also be fuel delivery. Try a fresh tank of gas and if it persists, change the filter and run a cleaner through. Start with the easy stuff before you pay for a diagnosis. Single cylinder misfires are usually coil pack followed by the injector fouling. Random means several cylinders failed to ignite in a revolution.

 

Thanks for the reply, Throttle.
This has been going on through several tanks of gas. Autozone couldn't find any codes. Remember, it's intermitant, plus I had to order the scanner and get it set up. I'm not the fastest critter, either. I'll pick up a fuel filter although I don't think that's it. Won't hurt anything, and neither will the cleaner. This just feels electrical, and I don't think it's the coils because it's pretty remote they'd all go bad at once. Do the coils get their signal straight from the computer?
I captured the problem last week too, but it didn't show a code at that time, just listed a misfire on each & every cylinder. I'll run the O2 tests too, as I haven't gotten much info on them yet. I'll post my findings as they come; I'd certainly appreciate any more ideas...
THANKS,

Dan

 

I could use some help here. This will random misfire for many revolutions at light load in overdrive, but the first couple of times it was doing it under higher loads, as cruising at 80 mph on the interstate, mostly uphill; I'm not talking mountains here by any means, just low rolling hills.
THANKS,

Dan

 

Have you pulled any plugs and looked at them, gap, condition? Might be worth a try and see what condition they are in...

 

Oh, I assumed you had pulled the code P0300 (random/Multiple misfire). The code is usually associated with corroded coils towers and fuel delivery, but you have individual coils in this truck. You might have to find a dealer with a "black box" engine monitor.

True fuel injector cleaner and fuel filter never hurts, but with the new information, I doubt it's the problem. The coils do get their signal through the computer, but fire sequence is manipulated through the cam and crank position sensors, but again they aren't tripping codes. You may want to perform a wiggle test on all connectors before going forward.

 

I did pull the PO300 code, but it was a pending code which was only there while the event was happening. The MIL isn't on, and no codes show now. The " wiggle test" sounds like it's going in the right direction, and it sounds like it's time to do some research on this type ignition system.
What is a "black box" engine monitor?
THANKS,

Dan

 

I have had several Fords come to the shop with the excact same problem. Ended up being build up of crap in the fuel rail. We did a fuel rail cleaning, and a motorvac, and cured the problem. May not be the same as your truck, just my .03 cents (yes .03 due to inflation).

 

The data analyzer (aka black box) is a system-wide data analyzer that plugs into your OBDII and it will log all parameters and malfunctions through the drive cycles. Some dealers have a really thorough device specifically programmed with all the manufacturer specific OBDII programs. There is an after-market device called the CarChip EX that does this also.

 

After Autozone couldn't pull a code from it, and I knew there had to be something there, I bought an Autoxray EZ Scan 4000. It will do most if not all of that. I pulled the P0300 code while driving down the interstate...turned the scanner on when the motor started acting up.
It's about 6 degrees and 5 inches of snow outside & my garage is so full of tools & engines I can't get the truck inside. Looks like I've got some cleaning to do before anything else. That's women's work!

Dan

 

After quite a bit of research, I have discovered my P0300 problem was due to a bad EGR valve. Also, I used some fuel injector cleaner too. My truck is an 1997 F150 with 4.2 Motor and 109k miles. This truck is on its second motor too because of the "Oil in Coolant" TSB/Problem


"However, if the (EGR) system is not gas-tight then air can be drawn into the inlet system instead of inert gas. This can weakens the mixture sufficiently to cause misfiring, and manifests itself as a noticeable misfire/hesitation at speed and light throttle, not present when accelerating. If the leak is serious enough it may manifest itself as a hunting/rolling idle, caused by an unmetered leak of air into the inlet"
---http://www.fordscorpio.co.uk/egrmonitor.htm


See also, below it is very insight full about what P0300 is calculated...


"Misfire Algorithm Processing
The acceleration a piston undergoes during a firing event is directly proportionate to the amount of torque it develops. A piston which is not subjected to a firing event will be 'dragged' round the power stroke instead of being 'fired' round it, and the rotational speed during this misfire will be slower than a satisfactory power stroke. The calculated piston acceleration value is compared to a misfire threshold that is continuously adjusted based on inferred engine torque.

The processing is then evaluated for noise. A misfire produces an assymetrical cylinder motion, while mechanical noise (driving over rough roads or high rpm/light load conditions) are symmetrical piston motion. Simply put, mechanical noise is where the firing stroke has taken place but the piston movement has been affected by 'snatching' on the transmission. Thus, deviant cylinder events of the symmetrical type are removed from the calculation and it is only the noise-free deviant accelerations which are labelled as misfires.

These misfires are then counted over a continuous 200 and 1000 revolution period. At the end of each period, the misfire rate for each cylinder is computed and compared to a engine/load threshold table in ROM. If the misfire rate exceeds this threshold on the 200 revolutions period and the PCM computes a risk of immediate damage to the washcoat in the Catalyst, this is a Type A misfire. In a MIL equipped vehicle the MIL light will flash while the misfire is occurring and the MIL light will illuminate at a subsequent event, and a DTC is stored. For the Scorpio there is no MIL light. On 6 cylinders engines the EECV may be able to disable the INJector to the affected cylinder, but this is not available to the 4 cylinder engines.

Next, the Misfire rate is calculated for the 1000 revolutions period and compared to another table of emission-threshold values to give a Type B misfire rate for any cylinder.

The Misfire Monitor runs continuously, calculating misfires every 200 and 1000 engine revolutions.

Entry Conditions
The Misfire Monitor entry conditions are:

Time since engine startup: 5 seconds before 1996, 240 seconds 1996-on vehicles
ECT - 0º F to 250º F
RPM - idle to 2,500 rpm

The Misfire Monitor is disabled when:

Closed throttle deceleration, (negative torque, engine being driven)
Fuel shut-off due to speed or revs limiting operation
Accessory load state change (eg, A/C compressor or power steering)
High rate of change of torque (flooring accelerator hard or lifting off suddenly) "
-- http://www.fordscorpio.co.uk/misfiremonitor.htm



Joe

 

EXCELLENT homework, Joe. I just noticed my last post (couple weeks ago) was evidently deleted. I have reason to believe someone added something to my gas (water?), so I put on a locking gas cap. I also added some Sea Foam to the gas. That took care of mine for a few weeks, but I had another minor case of it since. I'm going to try another can of Sea Foam, but I'll also check for air leaks.
My misfire also happened during the time the EGR would have been activated, but the MIL only came on for a short time, and was off by the time I got home. It never stored the P0300 code, I got that only when the problem was happening, with my scanner. I will certainly keep in mind what you came up with.
Dan

 

I have this identical problem

For abo0t 2 weeks now I have had it

IT is progressivly getting worse

I have changed fuel,fuel filter, PCV assembly, chaged/checked all Vaccum hoses, removed computer and cleaner terminals with no effect

I have unplugged the MAF for a drive to see if it would change with the different fuel tables and Tested the EGR with a vaccum pump , it almost killed the engine at idle (like it should)

This truck got it's plugs changed and tuneup abo0t one month ago and has been running VERY well up till this point

I made a thread abo0t it a week ago , here https://www.f150online.com/forums/sh...hreadid=144916

Well, today it Finally threw a new Code (since I cleared it a week ago) ....a P0300 *Random / Multiple Cylinder Misfire

When it first started it was only from 1500 RPM to 2000RPM ....now it is ALL over the RPM range

It surges and has no power at all

I am tired of laying in the snow trying to figure stuff out so it is going in the Shop (local Family Shop , Our local dealership is AWFULL)

Anyway, I hope you figue it out and please feel free to share info

BTW, I have 120K miles

Jon

 

Welp,

Just got back from a Dealer in another town ( TASCA )

I had 2 Coils missfiring and they Flushed my Fuel system on the BG machine

Truck Runs MINT!'

Anyway, I hope you guys have good luck with your problems

I HATE paying anyone to fix my stuff, but sometimes you just have to

Lata