My truck has been running like crap for a month and I finally got some trouble codes. I am actually happy that I now have I have the codes since trying to find out why your truck is hesitating and studering without wanting to spend a fortune is like finding a needle in a haystack...anyhow...
Now that I have these codes what do they mean? I am assuming they are misfire codes but I don't know for which cylinder. My search of the site didnt reveal anything.
Can anyone tell me where to start. I have changed out the plugs, airfilter, cleaned MAF, changed heater hose clamp above cylinder 4 (4.6), flushed tranny and changed fuel filter within the last 12000 km ( and of course oil change). I also looked for loose plug wires last night.
Please offer some advice.

 

P0300 is random Misfire. The PCM cannot identify which cylinderis misfiring. P0304 is Cylinder #4 Misfire. l Visually inspect the engine compartment to make sure all coils and spark plug wires are properly and securely connected.

Examine all wiring harnesses and connectors for damaged, burned or overheated insulation and loose or broken conditions.

Be certain the battery is fully charged.

Check the resistance in the plug wires. Should be < 7000 ohms per foot. If they are OK then check the plugs resistance. They should be between 2000 and 20000 ohms. You should also check the gap. The emissions sticker should have this speck. So far everything is free, if everything checks out then you probably are looking at a coil or a wiring problem.

Regards

Jean Marc Chartier

 

The code is P zero 30x not a lower case o, just to aid in additional searches.

I went and did a search to find where I already posted the manual excerpt on this DTC.

DTC
P0301 through P0310 Misfire Detection Monitor
Description
The misfire detection monitor is designed to monitor engine misfire and identify the specific cylinder in which the misfire has occurred. Misfire is defined as lack of combustion in a cylinder due to absence of spark, poor fuel metering, poor compression, or any other cause.

Possible Causes
-Ignition system
-Fuel injectors Running out of fuel
-EVAP canister purge valve
-Fuel pressure
-Evaporative emission system
-Base engine

Diagnostic Aides
The MIL will blink once per second when a misfire is detected severe enough to cause catalyst damage. If the MIL is on steady state, due to a misfire, this will indicate the threshold for emissions was exceeded and cause the vehicle to fail an inspection and maintenance tailpipe test.

The complete list for the search:
https://www.f150online.com/forums/sh...hlight=P030%2A
If you want to check what other members came up with ( beside JMC and myself in this post ).

Good luck getting to the bottom of it.

 

Thanks for the quick replies. I will try a search using the proper spelling lol!
I have a digital ohmmeter.. do I just pull the wire and divide by the length in feet of the wire? Im not very experienced with the tool so any instructions are more than appreciated.
Ex: which setting should i use on the tool?
I will post the results of the test tomorro, it looks like im not the only one who is having this problem lately.

 

That's all JMC was getting at in testing the wire itself.
If it is 2.4' then the ohms you should see on the meter are :
2.4*7000=16,800 ohms. So if you meter this wire it should have less then this amount of resistance.

Dumb question on my part, isn't a 99 a COP engine ?
I don't know if JMC had you checking the wires to the COP or if he was talking about normal spark plug wires ( which if it is COP it wouldn't have them ). I don't know which way it is, I have an '01.

Take a look at the list from the Manual on P0300 ( sorry I did not post that one earlier ). The random is part what JMC said, and part another poss problem.

DTC
P0300 - Random Misfire

Description
The random misfire DTC indicates multiple cylinders are misfiring or the PCM cannot identify which cylinder is misfiring.

Possible Causes
Camshaft position sensor (CMP)
Low fuel: less than 1/8 tank
Stuck open EGR valve
Blocked EGR passages

Diagnostic Aides
One or more EGR passages may be blocked or partially blocked. If this is the case the Misfire Detection Monitor will indicate the EGR port to check for possible blockage.

So with your truck being a '99 and a V6 which seems to have been know to have cases of blocked EGR ports ( which usually caused P0401 codes ) maybe this is the cause ofthe P0300 code.

Seeing how the Common between the P0300 and the P030x is the emission system, maybe starting there is a good idea. ??
Just a swag looking for commonality between the 2 DTCs.

Good luck, and let me know if I got that COPs thing wrong for '99, so I can try to recall it in the future.

 

scully,

COP started in 2000 on the 4.6.


JMC

 

That helps...thanks
Makes more sense now.

 

Great advice!
So far it is fixed. I changed the #4 plug even though it looked decent. I also checked the resistance in the wire and put dielectric grease on the wire and the injector connector. The miss is definitely gone.
It seems too good to be true...$5 fix?Cool. My next question would be could the new plug "hide" a weak coil pack? If so maybe I will keep the coil instead of returning it.
Thanks a ton JMC and sscully.

 

I am guessing that you did not install the new coil? If you did not, then by all means return it. If the coil was deffective the truck would still miss. The coil is one of the last things to check when there is a miss.

Regards

Jean Marc Chartier

 

I was wondering if anyone can send me in the right direction I have an 1998 F150 4.6l 4x2 Ihave been getting a P0304 dtc code on an off for over a year now, it has gotten so bad I cant drive more than ten miles without throwing this code. I have changed all plugs and wire no change even swaped out wires one more time to make sure swap colil packs same thing, changed tps, per a mechanic that didnt work either, changed fuel filterno luck, cleaned MAF truck ran good for about a week under acceleration I could feel the engine wanting to misfire but it didnt throw a code, now its back to running like crap, another mechanic said it could possibly the ( speed sensor ) does this sound possible or should I swap one of the injectors with number 4 to see if it throws code to another cly or should i have serviced by a dealer.
Any help would be greatly appreiated.

 

I would swap the injector with the #1.

.