420A Trouble code P1494

[98primeredrs]

What’s up guys I finally started to drive my 1998 Eclipse RS after painting it and it’s throwing the trouble code p1494. It threw this code at me before while I was doing all the bodywork and painting it but it said it was a Evap fault so I cleaned the connector for the vent solenoid and replaced the gas cap and the code when away.

After driving for about 100 miles and not having any issues besides using a lot of gas the check engine light popped on one morning when I cold started, so I plugged into the port and it was reading a P1494 but this time the scanner reads “FMA Mixture difference too high“. I search and couldn’t find anything with that definition. I asked a couple of guys at work and they told me that the fuel trims were too far apart and that’s what the code was on for.

Another thing to note is that every monitor was ready besides the heated O2 sensors. I ended up switching out the upstream O2 sensor because we had it in stock at work and cleared the code. The light stayed off for about a mile drive and then the next cold start it popped back on same definition as before but all monitors are ready.

Black Soot was on the exhaust tip so I’m assuming it’s running really rich which would make sense with the long term fuel trim for sensor 2 being at 99.2%. So I’m assuming it has a vacuum leak somewhere but it doesn’t have a high idle or anything like that and it runs good.

I’m really confused with this one. I enjoy driving the car and have put a good amount of work into so I would rather fix the issue then give up but It won’t pass smog the way it is right now. Any help will be much appreciated.

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[luv2rallye]

From my 1999 Mitsubishi factory manual:

 

[98primeredrs]

From my 1999 Mitsubishi factory manual:

Thank you very much I’ll test the LDP

 

[Sirius1995]

do leak detection test, make sure purge solenoid works, also for the fuel trim levels being too far apart, I'd say knock sensor is bad or fuel pressure regulator is messed up

 

[BLACK'98DSM]

Knock sensor on a 420a is completely useless unless you are using bad fuel or tampered with ignition timing.

You can completely remove the knock sensor and the car will run perfectly fine. I had one break on both of my engines and continued driving after. The check engine light does come on but the car doesn't run differently and the code will say something about knock detection.

With that being said, I agree that the fuel pressure regulator is a potential suspect.

 

[98primeredrs]

Knock sensor on a 420a is completely useless unless you are using bad fuel or tampered with ignition timing.

You can completely remove the knock sensor and the car will run perfectly fine. I had one break on both of my engines and continued driving after. The check engine light does come on but the car doesn't run differently and the code will say something about knock detection.

With that being said, I agree that the fuel pressure regulator is a potential

Knock sensor on a 420a is completely useless unless you are using bad fuel or tampered with ignition timing.

You can completely remove the knock sensor and the car will run perfectly fine. I had one break on both of my engines and continued driving after. The check engine light does come on but the car doesn't run differently and the code will say something about knock detection.

With that being said, I agree that the fuel pressure regulator is a potential suspect.

I tested the fuel pressure today it came back good kinda jumped between 40-50 at idle but stayed at 50 under a load.