420A 420a P0300 misfire code and idle issue

[Bryant O’Conner]

Hi all. I’ve had my 1999 Eclipse gs for about 2 years now. I have done a 5 speed swap and many more upgrades. Had a terrible lopey 383 stroker type idle for ever finally found out it was a tooth out of time couple days back. Now it idles great but still has a little tiny stammer like it used to but not no where close to how bad. I replaced plugs as they were fouled out from a richend mixture due to timing. And it helped a lil but not a lot.

Now I get Misfire Detected (P0300)
1 misfire(P0301)
2 misfire(P0302)
3 misfire(P0303)
4 misfire(P0304)

And it starts flashing when I get past 4K rpm but it runs so much better and it doesn’t seam like it’s missing. No other CELs or symptoms. All sensors are new as I was chasing problems when it was out of time before I figured it out. Thanks in advance

 

[Sirius1995]

Does it backfire?

 

[Bryant O’Conner]

No it just kind of stumbles a bit. But it’s barely noticeable. It fluctuates between 900 and 1200 at most

 

[evil_eagletalon]

Well it has to be something related to all 4 cylinders. Regardless i would start with the basics.

1.Compression test across the board.

2. Check fuel trims to see if the pcm is adding fuel or pulling it back.

3. Fuel quality test if tester is able to be used.

4. Verify base timing

 

[evil_eagletalon]

Does it backfire?

Suhh dude

Just noticed your a kia master. I am a hyundai master been with them since 2011.

 

[Sirius1995]

Suhh dude

Just noticed your a kia master. I am a hyundai master been with them since 2011.

Mr blue team, I've been with red since 2016 myself