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Discussion Starter · #1 ·
I just purchased a 2001 Mitsubishi Eclipse GT Spyder V6 3.0l that came from Arizona to here in California and have had the "Service Engine Soon" light on since I purchased the car from it's previous owner in Riverside County (I'm in Orange County). I put on a new Rotor and Distributor, new spark plugs (Double Platinum), wires, oil filter, EGR Valve, new hoses and new gaskets. My OBD2 reader said I had an issue with Bank 1 (Sensor 1) before all of this, but now I'm getting a "Misfire" (P0300). The car runs great except for the fact that every once in a while it seems to want to die at a stop light once I come to a complete stop. If I put it in neutral it will idle fine, but if I leave it in gear it seems to want to stall. I am at the end of my abilities and need to know if these cars have this issue alot. Any help or suggestions would be welcome... thank you.

Respectfully:
Beau
 

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Yeah, P0300 is a random intermittent misfire code, I've had this one myself. A few different things can cause that, such as too much air or too little fuel entering the engine. The fact that your car wants to stall out leads me to believe that you have a major vacuum leak somewhere. Use you're OBDII to check both banks' fuel trims. If they are positive and above ten you have a vacuum leak. If they are negative and below ten you have fuel restriction issues. Since you replaced the spark plugs, double check to make sure they are plugged in the correct firing order on the distributor.
43979
 

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Discussion Starter · #3 ·
Yeah, P0300 is a random intermittent misfire code, I've had this one myself. A few different things can cause that, such as too much air or too little fuel entering the engine. The fact that your car wants to stall out leads me to believe that you have a major vacuum leak somewhere. Use you're OBDII to check both banks' fuel trims. If they are positive and above ten you have a vacuum leak. If they are negative and below ten you have fuel restriction issues. Since you replaced the spark plugs, double check to make sure they are plugged in the correct firing order on the distributor. View attachment 43979
This is the reading I'm getting on my OBD2 reader for live monitoring... I think it might be a vacuum hose I missed or something of that matter.
43980
 

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Discussion Starter · #4 ·
Yeah, P0300 is a random intermittent misfire code, I've had this one myself. A few different things can cause that, such as too much air or too little fuel entering the engine. The fact that your car wants to stall out leads me to believe that you have a major vacuum leak somewhere. Use you're OBDII to check both banks' fuel trims. If they are positive and above ten you have a vacuum leak. If they are negative and below ten you have fuel restriction issues. Since you replaced the spark plugs, double check to make sure they are plugged in the correct firing order on the distributor. View attachment 43979
I also double checked the firing order and made sure each spark plug was correctly plugged and that all my rubber seals on the caps were in good condition and sealed correctly as well as the spark plug boots.
 

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You're running abnormally rich on Bank 2 at idle, I'm curious if that gets closer to zero as you drive or if it just gets worse? If it gets worse (like -25) that'll probably be the reason for your p0300 code. Check your PCV valve, the vacuum line to your fuel pressure regulator, data from your upstream and downstream O2 sensors on Bank 2 might give you some extra info. B2 sensor 1 should oscillate between 0.100V-0.900V and B2 sensor 2 should be flat lined at 0.500V, ideally, give or take .100. If either one is giving 0.000V than replace it. Make sure your fuel injectors aren't leaking. Sometimes an EGR valve stuck open will cause P0300. I doubt that would be that cause since you are running rich, but it wouldn't hurt to check.
 

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Discussion Starter · #6 ·
You're running abnormally rich on Bank 2 at idle, I'm curious if that gets closer to zero as you drive or if it just gets worse? If it gets worse (like -25) that'll probably be the reason for your p0300 code. Check your PCV valve, the vacuum line to your fuel pressure regulator, data from your upstream and downstream O2 sensors on Bank 2 might give you some extra info. B2 sensor 1 should oscillate between 0.100V-0.900V and B2 sensor 2 should be flat lined at 0.500V, ideally, give or take .100. If either one is giving 0.000V than replace it. Make sure your fuel injectors aren't leaking. Sometimes an EGR valve stuck open will cause P0300. I doubt that would be that cause since you are running rich, but it wouldn't hurt to check.
Will do... 👍
I'll post the results as soon as I check them. I'll check everything you've suggested and give an update on my findings. Thank you very much for your help in finding out what this issue may be. I really like the car and think it's a wonderful vehicle, It's an amazingly fun car to drive and is a pure joy to get around in (and I'm 53yrs old this year, think I found my midlife crisis. 👍💯🤣
Again, thank you VERY much for your help and suggestions.

Respectfully and Humbly:
Beau
 
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