car is running rich any idea's?

[fast_s13]

:help i have a 90 240sx with 67,000 mile's on it and it is running very rich. i have no mod,s done to the motor cause i am going to do a sr swap i just need to get it running good for summer

[ricebike]

just guesses...

leaking fuel injectors?

t-stat stuck open or temp sensor malfunction making the ECU think engine is still cold??

[fast_s13]

my injectors are leaking buut i think it might be the t-stat cause my heater dont blow hot thank for the help

[yellow_jacket]

Just curious, how do you know it is running rich?

[fast_s13]

air fuel ratio gauge....

[Nismo_Freak]

Did it just start to do this? I've noticed KA's run a little rich on the top end. A better indication would be to pull your plugs and inspect them. If they are light brown then dont worry, if they are black or deep brown then you are definately over fueling. This would be due to your thermostat and leaky injectors. Also the non wideband A/f gauges arent very accurate. It may be a malfunction with your 02 sensor.

[fast_s13]

my car runs rich from start up all they way till i shut it off..........could it have something to do with having a hollow cat?

[Nismo_Freak]

No ... the primary 02 is located before the cat. It must be the injectors overfueling as a result of the thermostat or leaks.

[fast_s13]

why would leaky fuel injectors make it run rich?

[Nismo_Freak]

If they leak into the manifold they can cause an overly rich mixture.

[fast_s13]

i think im going to go pick up a new thermostst tomorrow and try that since my heater isnt working right anyway

[JNM240]

I would also check your coolant temp sensor on your intake manifold. If the pigtail connection is green with corrosion, you need to replace it. If your coolant temp sensor is out, the ECU thinks the engine is cold and dumps extra gas into it, waiting for it to warm up.

[fast_s13]

i just repalced my o-rings on my fuel injectors and it didnt help any so next warm day i have im going to change the thermostat

[sethulrich]

if the coolant temp sensor is out, will it make the check engine light come on? also, is there another way to check it besides seeing if it's green with corrosion?