Running rich, mostly at idle

[PapaSmurf2k3]

OK, 91 240sx 5 speed 165k KA24DE, it progressively started running richer and richer, until it got so bad it sometimes stalled when coming out of gear. It does, however sometimes idle just fine, but more often then not its running weird (which leads me to beleive its electrical). The 02 sensor is about a year and half old, but i didnt think that the 02 sensor could control the air/fuel mixture that much. new plugs, wires, and I replaced the IACV, but it was from a 1990 because nissan changed the electrical connections. I have a greddy E-manage hooked up, with a profec E-01, (but the car isnt turbo yet) and all the voltages seem to check out OK. when its running rich, its running really rich, as in lots of black smoke coming out the exhaust rich. the only thing i can think of is maybe there is a vacuum leak somewhere and that is somehow causing it to run rich. Any ideas are greatly appreciated.

[PapaSmurf2k3]

bump... possible EGR problem? if so, how do I check this. I ran an ECU check and it comes up with injector leak, but I seriously doubt i have an injector leak, the injectors are new, and it doesnt smell like fuel like injector leaks usually do. Thanks.

[DAEDALUS]

Is the O2 sensor heated? If not it would have a hard time staying hot enough at idle to have any input to the ECU, so the ECU would go open-loop as a safety. O2 sensors can get carboned-up and give bad readings too. Need to open it up at WOT to burn things off if you havne't done so in a while. Maybe one or more injectors has a slight leak?

A vacuum leak would lean things out (more air) and raise the idle speed. How's the air filter? Clean? Check the MAF connection too.

[PapaSmurf2k3]

interesting... Ive definately done the WOT procedure quite a few times, thats usually my first reaction when something is wrong. But still, i dont think it would control the mixture that much. its running really rich at idle when its cold too. Dont injector leaks usually smell like fuel? I fiddled around with my E-manage to set it up to run leaner, ill see how that goes tonight. Thanks for the input.

[DAEDALUS]

Injector leaks smell like fuel only if the leak is on top of the injector. If at the bottom, the fuel goes straight into the intake. Won't smell it till it comes out the exhaust.

[PapaSmurf2k3]

OK, when you send injectors out to get flow tested, can you also get all of the seals replaced too? I just figure i should do that and cover all my bases. Also, where do you send them and how much does this cost?

[DAEDALUS]

The seals you replace on the outside when you replace the injector. Probably $10-15 for all of them from a dealer, just tell them you need the upper and lower o-rings for all injectors.I don't know anything about flow-testing, but you could do it yourself if you're willing to remove the fuel rail and you have a graduated cylinder or something similar.

[PapaSmurf2k3]

Can EGT cause me to run rich? I felt my exhaust the other day and it was really really hot, way hotter than usual. Do 240's even have EGT sensors? thanks again.

[DAEDALUS]

Only CA models have an EGT sensor and all they do is cut the fuel if the temp gets too hot I think (to prevent NOx formation). The timing could be off, causing the burn to happen late. Also, the engine could be running lean, which is opposite the symptoms you're seeing. BUT if 1 cylinder was running rich (from a leak), the O2 would pick up on it and try to lean everything down, so the other 3 would be lean and run hotter. Do a fuel rail leakdown test.