• The site migration is complete! Hopefully everything transferred properly from the multiple decades old software we were using before. If you notice any issues please let me know, thanks! Also, I'm still working on things like chatbox, etc so hopefully those will be working in the next week or two.

Engine code p0304 and p0300

A

Aaron85

New member
Hi new to the forum. I recently got a 2002 grand prix 3.8l non supercharged. Ive been getting a engine misfire code p0300 and p0304. Ive changed out plugs and wires, put in new coils also. I only get the code,at highway speeds 65 to 70mph im completely stumped at this point. Anyone have this issue or know what i can look for? Thanks in advance.

Sent from my SM-J700T1 using Tapatalk
 


Swap injectors around to rule those out. Swap the cylinder 4 injector for like cylinder 1 or 3. See if the misfire moves.

Past that it could be the ignition control module.
 
Hmmm Random Multiple Misfire and Cylinder 4 misfire as well. P00300 isn't a single cylinder causing the issue to set this code. Yet it's not seeing enough to set more codes and clearly #4 is bad enough to set that particular code. Check the connection at the ICM. Was there any corrosion when you pulled the coils?
 
BillBooost37 said:
Hmmm Random Multiple Misfire and Cylinder 4 misfire as well. P00300 isn't a single cylinder causing the issue to set this code. Yet it's not seeing enough to set more codes and clearly #4 is bad enough to set that particular code. Check the connection at the ICM. Was there any corrosion when you pulled the coils?
Click to expand...
No corrosion. I was getting p0300 regapped spark plugs now just getting p0304. If i pull wires off at the coils i get spark from each one. Im baffled at this point and it only happens at 65 to 70 mph after driving about 10 miles at that speed could it be caused by dirty injectors.

Sent from my SM-J700T1 using Tapatalk
 


Hey man just went through same thing lot of money wasted on trying different things end up being my downstream 02 sensor wish I tried this first would have saved a lot of money I changed both sensors they had 120000 on them.Dont know if this your problem but I was getting same codes.Good luck
 
daviddawg said:
Hey man just went through same thing lot of money wasted on trying different things end up being my downstream 02 sensor wish I tried this first would have saved a lot of money I changed both sensors they had 120000 on them.Dont know if this your problem but I was getting same codes.Good luck
Click to expand...
Damn yea i dont think i the downstream o2 sensor previous owner said someone tried stealing the cat and he straight piped it i know it has the upper o2 before the cat but idk about after

Sent from my SM-J700T1 using Tapatalk
 
What type of plugs did you install, and are you sure you got all the wires in the right order? It's easy to mix up some wires and it'll still run. Been there, done that.
 


FordMan77 said:
What type of plugs did you install, and are you sure you got all the wires in the right order? It's easy to mix up some wires and it'll still run. Been there, done that.
Click to expand...
Autolite platinums was real tight on cash and yes wires are in correct order

Sent from my SM-J700T1 using Tapatalk
 
One more thing before I replaced sensors car would run fine until it warmed up then I would start having the p0300 and p0304 codes
 
Aaron85 said:
Autolite platinums was real tight on cash and yes wires are in correct order

Sent from my SM-J700T1 using Tapatalk
Click to expand...

You said coils too...

Could be a simple mix up though still.

Order of everything should be like this if you're standing in front of it...

2 4 6
1 3 5

Coil order from top to bottom is

6
3
2
5
4
1

I'd also look into vacuum leaks. Usually you'd get a P0171 or something of the like but that can cause a misfire as well.

I personally would have ran cheap ass Autolite 606 copper plugs. They should have been much cheaper than Platinum's. Gap them to .050". Done and done.

By chance you didn't try to gap the platinum plugs, did you? lol
 
blueguy91 said:
You said coils too...

Could be a simple mix up though still.

Order of everything should be like this if you're standing in front of it...

2 4 6
1 3 5

Coil order from top to bottom is

6
3
2
5
4
1

I'd also look into vacuum leaks. Usually you'd get a P0171 or something of the like but that can cause a misfire as well.

I personally would have ran cheap ass Autolite 606 copper plugs. They should have been much cheaper than Platinum's. Gap them to .050". Done and done.

By chance you didn't try to gap the platinum plugs, did you? lol
Click to expand...
I did cuz i was told that they werent pre gapped. They are gapped to .045 right now

Sent from my SM-J700T1 using Tapatalk
 


daviddawg said:
One more thing before I replaced sensors car would run fine until it warmed up then I would start having the p0300 and p0304 codes
Click to expand...
Yea it runs fine cold and once i drive 10 to 15 miles on highway at 70mph is,when it starts. I can drive main roads all day with no problem

Sent from my SM-J700T1 using Tapatalk
 
Aaron85 said:
I did cuz i was told that they werent pre gapped. They are gapped to .045 right now

Sent from my SM-J700T1 using Tapatalk
Click to expand...

If they were the fine tipped plugs; then you most likely broke the wire up top on them. Yank all the plugs and check them. .045 is kinda small, too.
 
You must log in or register to reply here.
Back
Top