Random engine misfire code?

Tiny
BILL BIEBER
  • MEMBER
  • 2001 FORD RANGER
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 155,000 MILES
The temp gage failed motor locked down; tryed to restart motor not kowning that and battery shorted. I had the motor replaced with remanf. With new wires, plugs, ignition coil, and CKP. Service engine light came on when I got the truck home about 10mi. The shop looked a the codes and said that it said random misfire. They reset timing drove truck no light. U/P truck get home light returns and it did seem like it was missing on long slight grade. I returned to shop they checked the truck and said that the camshaft position rod needed to be replaced; that was done and now when you are in drive and it shifts from first to second gear about 3000RPMs it seem like it is reacting as though you were in park revving the engine and the RPM limitor is trying to restrain the engine and the light has returned. They want to replace the PCM now. What do I need to do to stop the misfiring and clear the code.
Friday, January 8th, 2010 AT 6:22 PM

28 Replies

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
P0300 normally points to vacuum leak and bad fuel

This guide can help us fix it

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

Engine misfiring could be caused by worn or fouled spark plugs, a weak spark (weak coil, bad spark plug wire), loss of compression, vacuum leaks, anything that causes an unusually lean fuel mixture (lean misfire), an EGR valve that is stuck open, dirty fuel injectors, low fuel pressure, or even bad fuel.
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Friday, January 8th, 2010 AT 6:33 PM
Tiny
RANGER78
  • MEMBER
  • 14 POSTS
  • 2001 FORD RANGER
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 95,000 MILES
When Im driving on the highway doing about 60 or so my truck starts shaking then my check engine light comes on and starts flashing if I slow down to under 60mph it goes off. The other day it stayed on solid so I took it to have the diagnostic error code read what up is PO302 misfire at cylinder 2. What could be causing this the truck seems fine when Im not driving faster than 60?
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Wednesday, July 29th, 2020 AT 11:04 AM (Merged)
Tiny
RASMATAZ
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Engine misfiring can be caused by worn or fouled spark plugs, a weak spark (weak coil, bad spark plug wire), loss of compression, vacuum leaks, anything that causes an unusually lean fuel mixture (lean misfire), an EGR valve that is stuck open, dirty fuel injectors, low fuel pressure, or even bad fuel.

P0302 Cylinder misfire at No.2-you should check the sparkplug, compression and injector for this cyl.
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Wednesday, July 29th, 2020 AT 11:04 AM (Merged)
Tiny
RANGER78
  • MEMBER
  • 14 POSTS
Well spark plugs wires coil egr valve are all less than 5 months old
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Wednesday, July 29th, 2020 AT 11:04 AM (Merged)
Tiny
RANGER78
  • MEMBER
  • 14 POSTS
What do you think is the most likely cause since it only occures when Im driving faster than 60mph?
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Wednesday, July 29th, 2020 AT 11:04 AM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
There's other things involved here such as the following

Oxygen sensor
Dirty fuel injectors (cleaning the injectors often fixes this).
Bad MAP (manifold absolute pressure) sensor
Bad TPS (throttle position) sensor
Bad or dirty MAF (mass airflow) sensor
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
Bad gasoline (fuel contaminated with water or too much alcohol)

Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include:

Dirty or worn spark plugs
Bad plug wires
Weak ignition coil
Wet plug wires
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Wednesday, July 29th, 2020 AT 11:04 AM (Merged)
Tiny
SHARRIS9US
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  • 1 POST
  • 2001 FORD RANGER
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 91,000 MILES
When driving between 40-50 mph my truck will buck, skip something and cannot figure what causes
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Wednesday, July 29th, 2020 AT 11:04 AM (Merged)
Tiny
RASMATAZ
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Check and test the following below:

Oxygen Sensor
Catalytic Converter
Dirty fuel injectors (cleaning the injectors often fixes this).
Bad MAP (manifold absolute pressure) sensor
Bad TPS (throttle position) sensor
Bad or dirty MAF (mass airflow) sensor
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
Bad gasoline (fuel contaminated with water or too much alcohol)

Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include:

Dirty or worn spark plugs
Bad plug wires
Weak ignition coil
Wet plug wires
Coil and Rotor
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Wednesday, July 29th, 2020 AT 11:04 AM (Merged)
Tiny
LEGACYHI
  • MEMBER
  • 1 POST
  • 2001 FORD RANGER
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 93,000 MILES
Just did a tune up on my rig about 4 months ago. Changed spark plugs, wires, and fuel filter. I have the oem air filter box still in the truck, but I replaced the filter with a k&n about a year ago. Anyways, I have done tune ups before on this truck and everything has always been fine. Since this last one however, I keep getting the check engine light coming on when it's idling. Brought it to napa, they checked the code, and it keeps coming back as "cyl 5 misfire". So I replaced that plug with a new one. Still doing it. My gas mileage is terrible. Usually I can get 240-260 miles per tank. Now I get about 180 if i'm doing good. Any ideas what might be the problem?
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Wednesday, July 29th, 2020 AT 11:04 AM (Merged)
Tiny
BLACKOP555
  • MECHANIC
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Do you have a separate coil for that cylinder?

Have you changed the spark plug wire as well? You can test it it should have no more then 10,000 ohms of resistance per foot of wire.

If thats all good and your getting good spark on that cylinder you should check the injector. Listen to it with a stethoscope and compare its sounds to other injectors. Sound the same or different?
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Wednesday, July 29th, 2020 AT 11:04 AM (Merged)
Tiny
AIRFRAMER1973
  • MEMBER
  • 3 POSTS
  • 2001 FORD RANGER
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 96,000 MILES
I got a misfire on cyl #1 (code PO301). I'm getting a blue spark on the spark plug. So that tells me the plug, plug wire and coil pack are good. I changed the plug about 3 mths ago when I first got the code, and it looks like it's never been used. It's not brown or black or anything. It's completely dry also. So, now I'm thinking fuel problem, right? I got 12.8 ohms on the injector itself, which is the same as the #2 injector. Ok, so that tells me the electrical side of the injector is good. I decided to clear the code. It did run a little better but I can tell the engine is still mising. The code has not popped again yet, but the check gauge light did blink a few times with a full tank of gas. All other gauges were normal. What's my next step? Can someone send me in the right direction?
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Wednesday, July 29th, 2020 AT 11:05 AM (Merged)
Tiny
BLACKOP555
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Try swapping the injector with another. If the problem moves with it you should replace the injector set. Because they run under the same conditions. Same fuel. One goes out so will otheres
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Wednesday, July 29th, 2020 AT 11:05 AM (Merged)
Tiny
DDP
  • MEMBER
  • 1 POST
  • FORD RANGER
Problem with a misfire on #4 (according to computer). Isolated to fuel injector problem and have been told that I need to do all 6 and not just 1. Can only one injector be pulled, checked and replaced/repaired or must all be done? This is a 2000 Ford Ranger.
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Wednesday, July 29th, 2020 AT 11:05 AM (Merged)
Tiny
KIN CHAN
  • MEMBER
  • 453 POSTS
Is okay to do one, but is more likely the rest are about the same condition as the defected one. Scope and volume test can verify the condition of the rest.
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Wednesday, July 29th, 2020 AT 11:05 AM (Merged)
Tiny
KASEKENNY
  • MECHANIC
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You can replace one injector at a time. That school of thought comes from people who only want to take apart the vehicle one time. So if there is something wrong with one just replace them all while you are there because they suspect the others are going to fail as well. However, I do not subscribe to this because if it is not broken I leave it alone. These injectors deliver the same fuel so unless the fuel is contaminated which caused the failure, I would only replace what is broken.

Here is the process for replacing the injectors.

Please reach out if there are issues. Thanks
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Wednesday, July 29th, 2020 AT 11:05 AM (Merged)
Tiny
MAXOOM
  • MEMBER
  • 1 POST
  • 2000 FORD RANGER
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 208,400 MILES
Shows misfire on cylinder 6. New spark plugs and wires. What else could it be?
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Wednesday, July 29th, 2020 AT 11:05 AM (Merged)
Tiny
MASTERTECHTIM
  • MECHANIC
  • 4,750 POSTS
Hello,

Lets start by checking the compression and the color of the spark plug which tells us if the injector is working. Here is a guide to help us get started.

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

Please run down this guide and report back.
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Wednesday, July 29th, 2020 AT 11:05 AM (Merged)
Tiny
FLETCHONE
  • MEMBER
  • 1 POST
  • 2000 FORD RANGER
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 85,048 MILES
I had a slight skip when driving. I replaced plugs and the skip was still there. I replaced wires and the skip is worse and misses on idle.? Help !
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Wednesday, July 29th, 2020 AT 11:06 AM (Merged)
Tiny
RASMATAZ
  • MECHANIC
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Engine running rough or misfiring can be caused by the following:

Defective spark plug
Inadequate spark/coil, defective spark plug wire.
False air leakage.
Faulty fuel injectors.
Insufficient fuel pressure.
Contaminated fuel.
EGR valve that is leaking.
Oxygen sensors.
Throttle position sensor.
Idle air control valve.
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Wednesday, July 29th, 2020 AT 11:06 AM (Merged)
Tiny
BRUEN1957
  • MEMBER
  • 1 POST
2000 ford ranger has a very temporary mis in it when first starting but not as long as it did before I replaced plugs and wires. When missing I can smell a little fuel for a second making me think its not an injector but ignition so I'm leaning towards a coil pack. Runs great all other times with 213000 on her. Any advice?
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Wednesday, July 29th, 2020 AT 11:06 AM (Merged)

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