# 97 Nissan eating gas!



## Bronx240sx (Sep 24, 2004)

Hey Guys,

I need help. My 97 240sx (auto) is running way too rich! It just spits out black carbon out of the exhaust. I did a smog pre-test and the CO2 measured at 15mph was 6.97 and at 25mph it's over 7.00. So far I've replaced the EGR valve but still no luck. There are no codes and no pending codes. Some people have suggested changing my O2 sensor since I have 109,000 miles, but I'm not sure that's the problem......any ideas would be greatly appreciated. Thanks.........


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## spec240sx (Aug 22, 2004)

Bronx240sx said:


> Hey Guys,
> 
> I need help. My 97 240sx (auto) is running way too rich! It just spits out black carbon out of the exhaust. I did a smog pre-test and the CO2 measured at 15mph was 6.97 and at 25mph it's over 7.00. So far I've replaced the EGR valve but still no luck. There are no codes and no pending codes. Some people have suggested changing my O2 sensor since I have 109,000 miles, but I'm not sure that's the problem......any ideas would be greatly appreciated. Thanks.........


Do what was suggested... The O2 should be replaced every 60k for proper running. Then buy 1 step colder plugs and gap them at the tight end.
This will create more burn and hotter spark. You should be fine then.
OR NOT.


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## Bronx240sx (Sep 24, 2004)

*o2 Sensors replaced - still no luck*

I had both o2 sensors replaced and still no luck! I'm still running rich! I heard some people mention "fsm" - can anyone tell me what that is and whether a nissan 240 has that? Thanks again for the previous reply.


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## HybridAndy (Jul 26, 2004)

FSM typically refers to a factory service manual. If you look online you can find .pdf versions but nothing beats actually have a real manual to look at and keep in the garage (my '90 240SX S13 manual was $90). 

I'm thinking fuel pressure regulator if it's running rich? It's job is to sit at the end of the fuel rail before the fuel return line and raise and lower the pressure in the fuel rail depending on engine vacuum. You can typically test them by hooking up a fuel pressure gauge and comparing the results before and after you remove the vacuum line running to it (what numbers you compare it to are in the FSM). If you don't have access to a fuel pressure gauge, you might even just consider replacing it, they're not terribly expensive. If the engine has been run rich for a while, a good tuneup might be in order as well (specifically new plugs as the old one's will have been fouled). With 109k miles, a new cap and rotor, wires, plugs and fuel filter would be a worthwhile investment anyway.


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## Bronx240sx (Sep 24, 2004)

Thanks for the insight on the manual. I'll see if I can get one. As far as the tune up goes, I've replaced everything - plugs, cap, wires, etc. The car's been running rich for about a month - I'm not sure if that ruins the plugs in that span of time, but I'll check them out. The fuel pressure regulator is the next step - I'll look into that. One last thing, the only progress (so to speak) was unsticking the EGR valve and then I decided to buy a new EGR valve. When we did this, the car seemed to run fine; but after a week everything started back up. So, I don't know if the EGR I purchased was faulty or got stuck again. Lastly, there's a similar yet smaller EGR looking device sitting right next to the EGR valve. There's a vacuum line that goes from the EGR valve to this other smaller looking EGR thing. Anyone know what that is?
Thanks guys!


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## rhynorock (Aug 7, 2004)

Are you sure you're not burning oil? I had a similar problem with my '94 Dodge Spirit, and as it turned out I had a bad piston ring, causing it to burn oil and expell this shitty, thick smoke out of my tailpipe. Check your PCV valve, if thats plugged, thatll cause the engine to burn oil as well.


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## Bronx240sx (Sep 24, 2004)

Well, after replacing the EGR valve and the O2 sensors, the real cause of the problem seems to be the EGR Solenoid Valve. When we disconnected the vacuum that goes from that to the EGR valve, the car no longer seems to be running rich. I guess I'm gonna be replacing the solenoid soon. Has anyone ever experienced a problem with the solenoid before?


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## spec240sx (Aug 22, 2004)

Bronx240sx said:


> Well, after replacing the EGR valve and the O2 sensors, the real cause of the problem seems to be the EGR Solenoid Valve. When we disconnected the vacuum that goes from that to the EGR valve, the car no longer seems to be running rich. I guess I'm gonna be replacing the solenoid soon. Has anyone ever experienced a problem with the solenoid before?


It is a rare situation. There may have been a surge of pwr and shorted the solenoid or there could still be a wire problem. I would suggest shooting the wire and/or visual inspection around the chasis and engine.


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