Misfire Code

Tiny
GIL17
  • MEMBER
  • 2015 FORD MUSTANG
  • 5.0L
  • V8
  • RWD
  • AUTOMATIC
  • 5,000 MILES
So this was my original problem my car was idling really weird like it wanted to turn off but then the revs would go back up. The check engine light was on and the Code "P2251 02 sensor Negative Current Control circuit/open", 2 other codes P0030 "H02S Heater Control Circuit" and P068A "ECM/PCM Power Relay De Energized Performance- Too early". I do have a tune, headers and CAI.. I had the tune, headers, and CAI for over a month with no problems. At first I thought it was the tune but somebody recommended to replace the faulty 02 sensor. So I did replace the 02 and the codes never appeared again. But now I have the same problem with revs going up and down but now I have a P0308 code "Cylinder 8 Misfire".I can't drive the car like this because is surges and shakes. I really don't want to take it to the dealership because of the Mods I have. I was hoping it was the tune because thats an easy fix but at this point I don't think it is. Any Advice?
Tuesday, October 6th, 2015 AT 2:06 PM

23 Replies

Tiny
RIVERMIKERAT
  • MECHANIC
  • 6,110 POSTS
Hello,

The oxygen sensor codes are normal when the engine is misfiring I would do a tune up using OEM parts here are two guides to help you to see whats going on.

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

and

https://www.2carpros.com/articles/how-to-tune-up-a-car-engine

Please run down these guides and report back.
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Wednesday, October 7th, 2015 AT 11:37 AM
Tiny
SUGAR132PLUMB
  • MEMBER
  • 8 POSTS
  • 2000 FORD MUSTANG
  • 3.8L
  • V6
  • 2WD
  • MANUAL
  • 190,000 MILES
I have a 2000 mustang that's giving me a cylinder 3 misfire code I've checked and rechecked the new plugs wires and alternator that was just recently put in. It ran fine for a month after I replaced the alternator for a clylinder 1 and cylinder 5 misfire code. I've suspected the ecm because I checked the idle air control valve which called for 5 volts but I kept getting a reading of 12 volts which the book said if the voltage is much higher. Than 5 volts have the ecm checked by a repair shop. I'm wondering though why I'm not getting an ecm code on my obd2 scanner. I'm also suspecting my egr valve because it will idle funny and it seems like the engine will overrev when I'm shifting gears I know a little about mechanics but am no expert and don't even know if an egr system problem would cause a cylinder 3 misfire code if anyone has had a similar problem with a fix I'd appreciate any insight on this.
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Wednesday, April 17th, 2019 AT 5:13 PM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
There is no code for an ecm on the type of scanner you have. A misfire can be caused by many things. It can be any sensor in the engine causing this. Things you can check are fuel pressure with a gauge-auto parts rent it and vacuum leak otherwise leave it to a pro with a different style scanner that can do a lot of other tests/things yours can't do. It willsave you money in the long run
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Wednesday, April 17th, 2019 AT 5:13 PM (Merged)
Tiny
RICKYRAU3
  • MEMBER
  • 1 POST
  • 2001 FORD MUSTANG
  • 6 CYL
  • 2WD
  • MANUAL
  • 187,000 MILES
It feels like im running on 5 cylinders, check engine is flashing.I had the same simptums 2 monthsago when drove thru alot of water, after drying it seemed fine
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Wednesday, April 17th, 2019 AT 5:13 PM (Merged)
Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
You may be running on 5 cylinders! When the MIL is flashing, it means catalytic converter could be damaged by the defect causing the MIL to flash, get the codes read and it will point you to the cause, could be an injector, or COP if yours has individual coils. Or bad plugs/wires.
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Wednesday, April 17th, 2019 AT 5:13 PM (Merged)
Tiny
SUGAR132PLUMB
  • MEMBER
  • 8 POSTS
  • 2000 FORD MUSTANG
  • 3.8L
  • 6 CYL
  • 2WD
  • MANUAL
  • 190,000 MILES
About a month ago I had a cylinder 1, and 5 misfire code I found out I had a bad diode in my alternator I replaced that and the problem went away for about a month I have all new plugs and wires and now a new alternator but now I'm getting a cylinder 3 misfire code any suggestions on how to further diagnose this.
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Wednesday, April 17th, 2019 AT 5:13 PM (Merged)
Tiny
CJ MEDEVAC
  • MECHANIC
  • 11,004 POSTS
Clear the code

Follow #3 wire, is it touching anything?

Inspect the places it may be touching for small, faint, gray arcing spots

Completely swap #3 wire with another wire

See if the code moves to that cylinder or if everything is good
.
.
.
Here's sorta what i'm basing my theory on

Maybe your problem is much like my niece's was

Well, my niece drug her '03 6 cyl. Mustang in here the other evening (well now, a few months ago)--been skipping and mostly shaking for a while.

My family's female philosophy: drive it till it won't go no more!

They sorta figured it was the plugs, but upon popping the hood while it was running, it sorta appeared to be having a really faint "light show" going on under there.

We replaced the plugs (as they had 'em on hand), as it had been time to do so long ago. This was not the problem though

But the light show was three different plug wires had rubbed "under hood stuff" until they were arcing on the metal components they touched one was on the hot manifold

The all time award winner was the one that was rubbing on the brake booster---it was gnawed a third of the way thru!

It was pretty obvious that whoever installed the old wires did not use much tlc, was in a hurry, thought nuthin' about future happenings

This time we installed new--lifetime warranty wires and routed the wires so they could not flop around.

I used wire ties and I purchased a few feet of 3/8 fuel line, I cut the fuel line into various lengths--split them and covered portions of the wires, every place a wire did rub/ or could rub/ or touch anything. The fuel line is a bit more durable than using plastic wire looms

That was the fix for her!

I'll stick with my jeeps

Hope this helps

The medic
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Wednesday, April 17th, 2019 AT 5:13 PM (Merged)
Tiny
AIRICA1105
  • MEMBER
  • 1 POST
  • 2000 FORD MUSTANG
I have a cylinder 4 misfire code, ive changed plugs wired coil pack o2 sensor, and still having problems, once she get warm I get a huge musfire almost like a fuel delivery problem, but not throwng a fuel code
I got hit on the passanger rear wheel well also when my gas tank filler tube it idk if that would do anything, but it wasnt a bad hit
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Wednesday, April 17th, 2019 AT 5:14 PM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Checkfor a vacuum leak like a hose off, leak at tbi something like that. If not that then have a pro diagnose it because these will drive you crazy trying to find out what it is.
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Wednesday, April 17th, 2019 AT 5:14 PM (Merged)
Tiny
STEAMBOATWILLY
  • MEMBER
  • 1 POST
  • FORD MUSTANG
I have a 2001 Mustang and the check engine light came on. I took it in today to have it looked at and all they got completed was the diagnositc test. The code that came up was P0301 Cylinder 1 Misfire Detected. The car is missing and hesitating some. What might need to be repaired?
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Wednesday, April 17th, 2019 AT 5:14 PM (Merged)
Tiny
SERVICE WRITER
  • MECHANIC
  • 9,123 POSTS
Depends on what is causing the misfire; that is compression loss, lack of spark or lack of fuel. Possible spark plug, or wire, fuel injector problem, intake leak are the first to come to mind.
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Wednesday, April 17th, 2019 AT 5:14 PM (Merged)
Tiny
KOKO.121
  • MEMBER
  • 34 POSTS
  • 2005 FORD MUSTANG
  • 4.6L
  • V8
  • RWD
  • MANUAL
  • 150,000 MILES
Hii I have a 2005 ford mustang GT V8 at my garage. I have a missfire problem on cylinders 5 and 8 I have replaced spark plugs, ignition coils, injectors plus I checked the feul pressure which is okey but a missfire is still present on the car and i'm getting these DTCs P0305, P0308, P0300 plus P0316 which is 'missfire on startup' anyone has a clue for a solution? Thanks in advance
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Wednesday, April 17th, 2019 AT 5:14 PM (Merged)
Tiny
WRENCHTECH
  • MECHANIC
  • 20,758 POSTS
Are you getting any oil or coolant leaking into the spark plug holes? I assume this has a Coil on plug system, right? They offered both in that year.
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Wednesday, April 17th, 2019 AT 5:14 PM (Merged)
Tiny
KOKO.121
  • MEMBER
  • 34 POSTS
Yes it is coil on plug system. And there is no oil or coolant leaking
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Wednesday, April 17th, 2019 AT 5:14 PM (Merged)
Tiny
WRENCHTECH
  • MECHANIC
  • 20,758 POSTS
You could have a burned out coil driver in the computer but you will need an electrical tech to do some testing to find out.
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Wednesday, April 17th, 2019 AT 5:14 PM (Merged)
Tiny
BRANDY0218
  • MEMBER
  • 2 POSTS
  • 2001 FORD MUSTANG
  • 103,000 MILES
I have a 2001 ford mustang gt with a 4.6 v-8. Check engine light came on, put on computer said #5 cylinder misfire. Which one is the #5? We have already replaced the fuel filter and all of the plugs plus the coil for the cylinder we thought was #5 but car Car is still acting up at speeds around 55-65 mph. Not sure what else to do! Hoping we just changed wrong cylinder coil.
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Wednesday, April 17th, 2019 AT 5:14 PM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Check your fuel pressure that can cause this as well. If it still does and your fuel pressure is ok then have your injectors checked.
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Wednesday, April 17th, 2019 AT 5:14 PM (Merged)
Tiny
BRANDY0218
  • MEMBER
  • 2 POSTS
Fuel pressure is fine and injectors have been cleaned still same problem
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Wednesday, April 17th, 2019 AT 5:14 PM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Check for a vacuum leak near that cylinder. Fuel pressure should be 35-45 if not that then it's to low. Check plugs for a piece of junk in between the electrodes and check compression. Spray choke cleaener around intake at cyl if it smooths out then that may be your problem also check the egr for staying open as well. It can also be torque converter clutch shudder especially if it stops when you accelerate or decelerate. If it is go to a trans shop they will have to change a switch or see if you have a sticking valve in trans.
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Wednesday, April 17th, 2019 AT 5:14 PM (Merged)
Tiny
JWTJ2125
  • MEMBER
  • 1 POST
  • FORD MUSTANG
My 2002 GT is mis firing on the #1 cylinder. I bought a new coil pack as advised to do. Only one problem. I am not sure which one is the number one cylinder. I thought that if you were facing the motor that it was the first one closest to the radiator on the right hand or driver's side. I changed it and it is still mis firing some. Some one let me know for sure which is the #1 cylinder
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Wednesday, April 17th, 2019 AT 5:14 PM (Merged)

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