SPONSORED LINKS

My engine is misfiring?

Tiny
GJEWELL
  • MEMBER
  • 1996 CHEVROLET CAVALIER
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 86,600 MILES
1996 Chevy Cavalier ls misfire error code P0300 multiple random misfire. The catalytic converter and the area around the the oxygen sensor is red after a mile, is this a symptom or the cause of the misfire?
Monday, November 29th, 2010 AT 12:46 AM

54 Replies

Tiny
ERNEST CLARK
  • MECHANIC
  • 1,730 POSTS
Yes it is. It means raw fuel is being dumped into the exhaust and burning down stream. You need to get this fixed before it fouls the converter. Most likely your coil pack is faulty. Here are two guides to help us fix the problem.

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

and

https://www.2carpros.com/articles/how-to-test-an-ignition-system

Please run down these guides and report back.
SPONSORED LINKS
Was this
answer
helpful?
Yes
No
+1
Monday, November 29th, 2010 AT 12:49 AM
Tiny
GJEWELL
  • MEMBER
  • 7 POSTS
I have replaced coil pack, plugs, I.C.M, and injector seals.
Could it be fuel pump regulator or fuel pump?
Was this
answer
helpful?
Yes
No
Monday, November 29th, 2010 AT 12:52 AM
Tiny
ERNEST CLARK
  • MECHANIC
  • 1,730 POSTS
No. You are getting fuel in the cylinders, but it's not firing. You can however test the pump pressure to be sure, but then pull the plugs one at a time and see if they are being fouled by fuel. If they are, look for a leaking pressure regulator, as sometime it will introduce too much fuel into the intake and foul the plugs.

Next look for leaking injectors. This has nothing to do with the seals around the outside of the injectors. This will be an internal leak that allows fuel to go into the cylinders at the wrong time, which will then go out the exhaust valve unburned.
Was this
answer
helpful?
Yes
No
Monday, November 29th, 2010 AT 12:58 AM
Tiny
GJEWELL
  • MEMBER
  • 7 POSTS
Its random but there are usually 2 'sooty' plugs and 2 'wet' plugs. Random asto in what order.
Injectors checked o.K. While out, compression is o.K. Also.
Fuel pressure regulator is discolored.
The fuel pump can be heard but I did try without fuse and it made no difference to engine performance?
Was this
answer
helpful?
Yes
No
Monday, November 29th, 2010 AT 1:14 AM
Tiny
GJEWELL
  • MEMBER
  • 7 POSTS
The fuel rail is also discolored around the base of the regulator!
SPONSORED LINKS
Was this
answer
helpful?
Yes
No
Monday, November 29th, 2010 AT 1:16 AM
Tiny
ERNEST CLARK
  • MECHANIC
  • 1,730 POSTS
That would be an external leak. That may also be a problem, but keep in mind, there are two kinds of misfires, ignition and lean. An excessively lean condition will cause your exhaust to overheat and glow red, but it's not as common a condition as unburned fuel entering the exhaust and being burned inside the tail pipes or causing your cats to light off.

I'm not always 100% correct, as no one is perfect. But I believe your misfire is causing this second kind of condition. Unfortunately it's not always easy to hunt down. You just have to go one step at a time until you find the problem. But remember to test, not just replace parts. Only replace when you know that part is faulty.
Was this
answer
helpful?
Yes
No
Monday, November 29th, 2010 AT 1:23 AM
Tiny
GJEWELL
  • MEMBER
  • 7 POSTS
I have replaced 2 coils, coil pack housing, I.C.M, plugs and boots what else could cause a misfire?
What should fuel pressure regulator pressure be if a gauge was used?
Was this
answer
helpful?
Yes
No
Monday, November 29th, 2010 AT 1:38 AM
Tiny
ERNEST CLARK
  • MECHANIC
  • 1,730 POSTS
First pull the vacuum line to the regulator and check for the presence of fuel. If there's any, replace it.

Fuel pressure should be 41-47 psi.

There are MANY things that can cause a misfire, including but not limited to:

Bad computer, failing sensors, you forgot to put the dielectric grease around the insulators of the plugs when you replaced them, there's a bad ground to the coils, the coils wires, connectors are bad, the injectors are clogged/leaking, etc.

The thing to do is eliminate one thing at a time, beginning with the ignition system, then fuel, then sensors, then computer.
Was this
answer
helpful?
Yes
No
Monday, November 29th, 2010 AT 1:55 AM
Tiny
GJEWELL
  • MEMBER
  • 7 POSTS
It was the fuel injectors cause the issue this guide helped me find it.

https://www.2carpros.com/articles/how-to-test-a-fuel-injector

Thank you for the help, it is much appreciated.
Was this
answer
helpful?
Yes
No
Monday, November 29th, 2010 AT 1:59 AM
Tiny
MARY HERRON
  • MEMBER
  • 1 POST
  • 1996 CHEVROLET CAVALIER
  • 4 CYL
  • FWD
  • MANUAL
  • 194,200 MILES
What could cause my car to start missing. It starts and idols but has a bad miss, no power. It has not made the check engine light come on. The plugs are firing, compression is ok, What could be the problem?
Was this
answer
helpful?
Yes
No
Friday, October 16th, 2020 AT 11:30 AM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Engine running rough or misfiring can be cause by the following:

1.Defective spark plugs
2.Inadequate spark/coil,defective spark plug wire.
3.Lack of compression

Goover this guide to help find out which one

https://www.2carpros.com/articles/engine-misfires-or-runs-rough
Was this
answer
helpful?
Yes
No
+4
Friday, October 16th, 2020 AT 11:30 AM (Merged)
Tiny
CODYM0724
  • MEMBER
  • 3 POSTS
  • 1995 CHEVROLET CAVALIER
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 122,000 MILES
I have a 95 cavalier just had the head gasket redone and everything was good till about 1 day later and all the sudden my car was idleing real rough bouncing between 600 and 800 rpm and I replaced the plugs had the sensors checked it all came up good and we ran the diagnostic tester on it and I had no check engine light on but it came up as random misfire but would not say where my mechanic thought it was vacuum lines but that was good too im just wondering what is going on with this junker, I also have what appears to be fuel in my intake because I take the whole air cleaner assembly off and at he bottom there is liquid and it is not oil and I replace the fuel filter to and fuel injector o rings
SPONSORED LINKS
Was this
answer
helpful?
Yes
No
Friday, October 16th, 2020 AT 11:31 AM (Merged)
Tiny
SERVICE WRITER
  • MECHANIC
  • 9,123 POSTS
Random misfie. Head gasket just done.I think I would have the compression tested in the cylinders. Perhaps the head is cracked or gasket instalation problem, gasket defect etc.
Was this
answer
helpful?
Yes
No
Friday, October 16th, 2020 AT 11:31 AM (Merged)
Tiny
CODYM0724
  • MEMBER
  • 3 POSTS
What would make the gasket not install properly just wondering?

Now the motor is starting to tick a little bit sounds like a lifter should I replace the head gasket and all the other gaskets again?
Was this
answer
helpful?
Yes
No
Friday, October 16th, 2020 AT 11:31 AM (Merged)
Tiny
SERVICE WRITER
  • MECHANIC
  • 9,123 POSTS
Incorrect tightening sequence or incorrect torquing.

I understan dyou unplugged a sensor but need identification? Can you give the location and or a pic? How many wires go to it?
Was this
answer
helpful?
Yes
No
Friday, October 16th, 2020 AT 11:31 AM (Merged)
Tiny
HOTRODLANEY
  • MEMBER
  • 4 POSTS
  • 1994 CHEVROLET CAVALIER
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 164,000 MILES
On the expressway (& car warmed up), when aproaching the speed of 45-55 mph the car starts to shudder (shake) and is fine once I get it past there. Then once the cars been run and I am coming off the expressway down the ramp and am almost to a stop the car jerks hard like its gonna stall and sometimes does. What could the problem be?
Was this
answer
helpful?
Yes
No
Friday, October 16th, 2020 AT 11:31 AM (Merged)
Tiny
RHALL77
  • MECHANIC
  • 3,361 POSTS
Is there a chec engine light on?
Was this
answer
helpful?
Yes
No
Friday, October 16th, 2020 AT 11:31 AM (Merged)
Tiny
HOTRODLANEY
  • MEMBER
  • 4 POSTS
No, there is no check engine light on.
Was this
answer
helpful?
Yes
No
Friday, October 16th, 2020 AT 11:31 AM (Merged)
Tiny
RHALL77
  • MECHANIC
  • 3,361 POSTS
When was the last time you had a tune up
Was this
answer
helpful?
Yes
No
Friday, October 16th, 2020 AT 11:31 AM (Merged)
Tiny
HOTRODLANEY
  • MEMBER
  • 4 POSTS
Just had a tune up 2 months ago
Was this
answer
helpful?
Yes
No
Friday, October 16th, 2020 AT 11:31 AM (Merged)

Please login or register to post a reply.

Related Engine Misfire Content

Intermittent Misfire
VIDEO
Intermittent Misfire
Instructional repair video
Misfire Random Code P0300
GUIDE
Misfire Random Code P0300
The world of automotive diagnostics can be complex, with numerous codes and potential issues to keep track of. One of the more common engine diagnostic codes is P0300, which...
VIEW MORE

Sponsored links