If your ECU controls your A/F mix. How does your car run lean? I took my plugs out on sat and they were frosty white looking. I did a search and read that it means I'm running lean. But I don't understand how I can be doing that since everything is automatic with our ECU's. Did I miss somethin?

Background-
97 I30t 5 spd
CAI/Ypipe/CAT/catback.

65k miles without 60k mile services.

 

This might help explain it:
http://forums.maxima.org/showthread....highlight=0510

See DBM's second post in the thread. basically, when the ECM is in closed loop mode, the fuel injection system runs the opposite of what the o2 sensors are reading.

I don't remember what codes you were throwing, but this may explain the plugs.

 

I was getting Knock sensors and rear heated 02 sensors errors. But I still dont see how all this works.--

So when you are driving and you have a CEL, are you stuck in an open loop?

 

Open loop is until the engine is hot enough for the o2 sensors to start working.

Once the o2 sensors are hot enough to start working, the ECM kicks into closed mode.
The ECM tries to balance the ratio. If your o2 sensor is reading rich, it signals the fuel injection system to run lean. If the o2 sensors are reading to lean, the fuel injection system is signaled to run rich.

Closed loop mode is supposed to keep everything balanced.

So, if your o2 sensors were reading that you were running to rich, the ECM is telling the fuel injection to run lean, thus frosty white looking spark plugs.

 

Ahhh thank you for letting me see the light

 

wow.. i learned something new today..

 

That could be part of your problem too.

 

Exactly. Your ECU may be trying to compensate for plugs that are just plain done. I read a thread somehwere of this guy who worked at an auto rental place working on their cars. He was amazed how several fleet cars would seemingly work fine even though their plugs were shot.


DW