Super Lean (16:1)

[S14DB]

My check engine light came on with a MAP/BARO switch error. Replaced the switch but it still comes up. Went to a dyno day anyways cause the car was running fine. Pulled a 16:1 A:F ratio.

I have an Injen CAI, OBX header and 5zigen Fireball.

Is it the code or the mods? do I need a SAFC? How can I fix the code?

[kidinthehall]

16:1 where though. cruise, wot, what?

[nightwalker]

if you replaced the switch and the code still come up it's obviously not the switch. Time to check the connector and wiring, as well as the wires on the ECM side. If it's three wires, you should have a ground, reference voltage(5volts) and signal voltage(varying voltage) if just two wires, then just ground and signal. Pull off the connector and back probe the wires. Also back probe with the connector connected. Then check the wires at the ECM. You'll find your problem.

[S14DB]

16:1 where though. cruise, wot, what?
16:1 at WOT

[kidinthehall]

where at in the powerband? got a pic of the a/f graph?

[S14DB]

don't have a scanner at home will scan on monday.

[brage]

check MAF, fuel filter, fuel pressure (should be ~43psi @ idle w/o the vacuum line connected), injectors...

-j

[S14DB]

I got a 300zx filter.
You hose the MAF down with Non-Clor. Brake cleaner?
I have a Fuel Pressure tester from my mustang. what kind of adapter do I need?

[S14DB]

http://img.photobucket.com/albums/v108/S14DB/240sx/dyno.gif

[nightwalker]

think about it. You know what the map/baro sensor on the 240 si for? It's to read atmospheric pressure. So your engine is leaning itself out. WHY? Because there is a problem with the Baro sensor. But since you switched the sensor, that is not the problem. So the other only problem could be in the harness, or ECM. What's happening is the sensor thinks it's at a higher altitude, that's why you are getting a lean a/f ratio. The sensor reads off of voltage, and if there was a short or something in the wire/computer driver/plug, it would cause a low voltage reading, so the sensor is not getting the right reading, so therefore it thinks it's at a higher altitude. Low voltage output= high altitude/ High Voltage output= lower altitude.

The map/maf/tps/ect sensors are load sensors and take precedence over the o2 sensor, so no matter what you do with a AFC because of the o2 reading, it's not going to help.

like I said, go and backprobe the plug to see what the voltage readings are. Or you could keep replacing parts and hoping something will fix it. :duh: