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Engine misfiring?

Tiny
JOHNBANKS
  • MEMBER
  • 2001 HYUNDAI ACCENT
  • 4 CYL
  • FWD
  • MANUAL
  • 120,000 MILES
I have a 2001 Hyundai Accent that suddenly starting missing badly, with the Check Engine Light coming on and flashing. The engine had low power, and there was a fairly strong gassy smell. The engine misses were noticeable both at idle an full speed.

I had the codes read, and there was a P0300, and P0304. I figured this could be spark plug or wire, but is this consistent with the strong gas smell?

Thanks for your help!
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Tuesday, May 5th, 2009 AT 9:06 PM

15 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,867 POSTS
PO300 Random misfire

PO304 Cylinder 4 misfire.

Has the vehicle been tuned up? Have you tried cleaning your fuel injectors? Also, lets go over this guide which will tell us what's going on

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

Please run down this guide and report back.
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Tuesday, June 2nd, 2009 AT 9:17 AM
Tiny
JOHNBANKS
  • MEMBER
  • 16 POSTS
Thank you for your reply. It turns out it was a defective #4 spark plug wire. Strange thing was that within 1 week of replacing the plug wires, the car began to miss again in a similar fashion. Same codes reappeared, and when I checked the #4 plug wire, I could again see a crack on the upper boot that looked very similar in placement to the last one.

They were lifetime wires, so I took them back, and have not so far had the problem reappear. Should I just chalk this up to bad wires, or could there be something else causing this?
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Sunday, June 7th, 2009 AT 10:14 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,867 POSTS
I would say you got a bad wire. If it happens again, let me know.

Joe
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Monday, June 8th, 2009 AT 12:07 AM
Tiny
GLHILLYER
  • MEMBER
  • 2 POSTS
  • 2000 HYUNDAI ACCENT
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 175,000 MILES
I just replaced the Plug Wires and spark plugs in my 2000 Hyundai Accent, for the 3rd time in 18 months. Each time, a different cylinder has begun to misfire, and the parts replacement resolved the problem. I use Autolite replacement wires and NGK plugs. Why are the wires failing? I need to replace the Mass Air Flow Sensor, as the Check Engine light is always on, but that's nearly $300. Could the bad sensor be affecting wire life?
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Sunday, December 6th, 2020 AT 8:24 AM (Merged)
Tiny
ZACKMAN
  • MECHANIC
  • 4,202 POSTS
MAF sensor has little to do with your plug wires. I had a problem with a Sonata a while back, and problem was solved using platinum plugs. In your case, it is (BKR5EGP - 7090) or (BKR5EIX-11 - 5464). Also, use dielectric grease between the plug boots and the plug tips.

When the CEL turns on, does it indicate that the MAF sensor bad? If it is, you should take the sensor unit out of the filter hose, and try cleaning it with sensor-safe cleaner such as CRC Mass Air Flow Sensor Cleaner 05110. I had a Sentra that had a piece of hay stuck on the sensor. Don't ask how the hay got there in the frst place.
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Sunday, December 6th, 2020 AT 8:24 AM (Merged)
Tiny
BGALE1
  • MEMBER
  • 1 POST
  • 2000 HYUNDAI ACCENT
  • 4 CYL
  • FWD
  • MANUAL
  • 180,000 MILES
My scanner read po0300 Random missfire, po0301, po0302, and po0304.

The timing belt was replaced about 17,000 miles ago.
I have replaced the spark plugs and the spark plug wires. It has a healthy spark when testing the spark. I did find a bad spark plug on the right side outer cylinder. It probably was not firing at all. When you listen to the exhast from behind the car it sounds like it is not firing on one cylinder, hence the po0300 code. Any ideas as to what may be wrong?
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Sunday, December 6th, 2020 AT 8:24 AM (Merged)
Tiny
MHPAUTOS
  • MECHANIC
  • 31,937 POSTS
Hi there,

This could well be an electrical problem. A faulty lead will do this, but to fully check the ignition system, have a diagnostic run on an oscilloscope, this will give your mechanic a full "visual"of the ignition pattens and voltages, including the miss fire, this will make tracking down the problem simple.

Mark (mhpautos)
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Sunday, December 6th, 2020 AT 8:24 AM (Merged)
Tiny
VHUTCHISON
  • MEMBER
  • 1 POST
  • 2000 HYUNDAI ACCENT
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 91,000 MILES
In town when I turn the air on engine is very sluggish and starts missing almost. If you stop at a stop light and try to start out there is a big lag and sometimes will die.
The heat has really increased this. If you turn air off - everything is fine again. What is causing this?
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Sunday, December 6th, 2020 AT 8:24 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,867 POSTS
Has the engine light ever come on?
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Sunday, December 6th, 2020 AT 8:24 AM (Merged)
Tiny
VILLIERS88
  • MEMBER
  • 1 POST
Sorry to say but thats what all of them do. The motor is only a 1.5L and can't handle it when the AC is on. But if its really bad try checking your spark plugs and leads.
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Sunday, December 6th, 2020 AT 8:24 AM (Merged)
Tiny
SEAN1876
  • MEMBER
  • 1 POST
  • 1999 HYUNDAI ACCENT
Engine Performance problem
1999 Hyundai Accent 4 cyl Front Wheel Drive Manual

i have a 99 accent. It has an engine miss which I have tested numorous times, and every message I get is a misfire on number 4 cylinder. I have changed the plugs, wires, coil pack 3 times, and the feul injectors. I still continue to have the same problems. I know the oxygen censors may need to be changed, but the engine just has no power unless you ease the gas pedal down slowly. Then it has full power until I get abour 3/4 of the way to full accelartion, then it cuts out. I have done a compression check on each cylinder and have 150 psi on each. I dont know what else to check. Any suggestions would be appreciated. Thanks.
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Sunday, December 6th, 2020 AT 8:24 AM (Merged)
Tiny
MHPAUTOS
  • MECHANIC
  • 31,937 POSTS
Hi there,

I would be checking for a vacuum leak and get the ignition checked on an oscilloscope as this will help pin point any ignition problems, start here.

Mark (mhpautos)
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Sunday, December 6th, 2020 AT 8:24 AM (Merged)
Tiny
GERRY1963
  • MEMBER
  • 1 POST
  • 1999 HYUNDAI ACCENT
Engine Performance problem
1999 Hyundai Accent 4 cyl Front Wheel Drive Automatic 165k miles

got a po301 code what should I look at?
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Sunday, December 6th, 2020 AT 8:24 AM (Merged)
Tiny
MHPAUTOS
  • MECHANIC
  • 31,937 POSTS
Hi there, simple things first, check lead. Plug, and compression, start here.

Mark (mhpautos)
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Sunday, December 6th, 2020 AT 8:24 AM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Check spark plug, compression and fuel injector on #1 cylinder.
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Sunday, December 6th, 2020 AT 8:24 AM (Merged)

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