Why is my engine Misfiring?

Tiny
CJOHN14
  • MEMBER
  • 2003 FORD RANGER
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 81,000 MILES
My check engine light came on and says several cylinders were missfiring so I changed the spark plugs. The problems still persist when I hit 3700 rpms the motor begins to missfire and you can hear valves clacking. Also when stopped the truck idles at 500 rpms which I thought was very low. Whats the problem?
Sunday, February 21st, 2010 AT 2:19 PM

13 Replies

Tiny
MATHIASO
  • MECHANIC
  • 1,209 POSTS
Hello cjohn14

Water in the fuel could cause the random misfire(bad gas)or the ignition coil is causing the problem.

Please go over this guide

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

check also for a vacuum leak in the intake manifold, throttle body or vacuum plumbing, a defective Exhaust Gas Recirculation (EGR) valve that is leaking exhaust into the intake manifold.

Ignition coil removal


https://www.2carpros.com/forum/automotive_pictures/46384_0996b43f80202d6c_2.jpg

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Sunday, February 21st, 2010 AT 6:56 PM
Tiny
NIDA PITTS
  • MEMBER
  • 3 POSTS
  • 2003 FORD RANGER
  • 6 CYL
  • 2WD
  • MANUAL
  • 140,000 MILES
I have a 2003 ford ranger runs great but is missfiring at 60 or above speed. The engine light does not come on during this. I have changed spark plug wires. What could it be?
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Wednesday, July 29th, 2020 AT 11:00 AM (Merged)
Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
Check the fuel pressure, the pump could be on the way out, any trouble with hill climbing?
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Wednesday, July 29th, 2020 AT 11:00 AM (Merged)
Tiny
NIDA PITTS
  • MEMBER
  • 3 POSTS
Yes that is when the missing is the worse
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Wednesday, July 29th, 2020 AT 11:00 AM (Merged)
Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
Test pressure and get back to us.
https://www.2carpros.com/car_repair_video/test_fuel_injection_pressure.htm
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Wednesday, July 29th, 2020 AT 11:00 AM (Merged)
Tiny
NIDA PITTS
  • MEMBER
  • 3 POSTS
  • 2003 FORD RANGER
  • 6 CYL
  • 2WD
  • MANUAL
  • 140,000 MILES
2003 ford ranger missfiring
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Wednesday, July 29th, 2020 AT 11:00 AM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Engine running rough or misfiring can be cause by the following:

1. Defective spark plug.
2. Inadequate spark/coil, defective spark plug wire.
3. Lack of compression
4. False air leakage.
5. Fautly fuel injectors.
6. Insufficient fuel pressure.
7. Contaminated fuel.
8. EGR valve that is leaking.
9. Oxygen sensors.
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Wednesday, July 29th, 2020 AT 11:00 AM (Merged)
Tiny
TERRYC427
  • MEMBER
  • 1 POST
  • 2003 FORD RANGER
  • 128,000 MILES
Been experencing an engine miss on occassion. Seems to happen when moisture gets into the engine compartment, like after a rain. Then when the compatment dries out the miss either goes completely away, or is barely noticeable.I replaced the plugs about 6 months ago but not the wires, which appeared to be in good shape. Wires to my knowledge are the factory origionals. Could the problem be the wires just need to be replaced since they have 128,000 on them.
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Wednesday, July 29th, 2020 AT 11:00 AM (Merged)
Tiny
IMPALASS
  • MECHANIC
  • 3,112 POSTS
Sparks can still be jumping from the wires even though they look normal to the eye. Sometimes you can open the hood at night and make sure it is a dark as possible and you can see sparks jumping.

Also, take a spray bottle with water in it and start the car. With it running mist water over the various plug wires. When the engine shuttlers there is your spark jump and bad wires.
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Wednesday, July 29th, 2020 AT 11:00 AM (Merged)
Tiny
BLONDEBEARD
  • MEMBER
  • 3 POSTS
  • 2003 FORD RANGER
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 108,000 MILES
NO obd 2 codes, runs great till warm up (closed loop), then misfires up hill, under load or just revving engine. Have new coil pack, wires, plugs. Fuel pressure is 61 psi (normal). With master obd 2 computer, shows mixture stays lean above 3200 rpm (no computer correction). Replaced the front two oxygen sensors but not the back two. Also intermittent rough idle. Any Ideas?
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Wednesday, July 29th, 2020 AT 11:00 AM (Merged)
Tiny
2CARPRO JACK
  • MECHANIC
  • 11,533 POSTS
Most likely the Mass Airflow Meter is out of range. They dont always set a code, but will do exactly what you describe. You can try a special cleaner for them, but I personally havent had any luck with that fix lasting. Always use an OEM part (Ford)
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Wednesday, July 29th, 2020 AT 11:00 AM (Merged)
Tiny
BLONDEBEARD
  • MEMBER
  • 3 POSTS
Ok thank you, I will replace it and keep you posted on what happens.
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Wednesday, July 29th, 2020 AT 11:00 AM (Merged)
Tiny
BLONDEBEARD
  • MEMBER
  • 3 POSTS
Well, put in new mass airflow meter and now the idle is perfect (was running rough also) but still misfires above 3200 rpm. By the way, its a small band of misfire, above 4000 rpm, misfire stops.
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Wednesday, July 29th, 2020 AT 11:00 AM (Merged)

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