hay org family...came across a problem recently with my 99 5 speed max... i noticed my car will run lean when cold on my wideband to the point where it will line out and cause the car to idle funny...i replaced all the upstream primary o2 sensors and put new brk5 ngk spark plugs in...as soon as the car warms up it goes away...i checked for vacuum leaks but didnt cross any and i reseted the ecu just in case it was in loop mode... any suggestions?

 

unplug MAF > Check
Unplug O2 B1 > Check
Unplug O2 B2 > Check
Test Different ECU > Check

 

imma try replacing the coolant temp sensor since that has something to do with the afr fluctuation...i remember i through a code for that before then it not showing up again

 

ok i replaced the cts and there was a slight improvement but still idles around 16 when cold...any idea anyone?

 

bump

 

You could always clean the MAF if you haven't done that in a long time. My 3rd gen was running lean and I gave the MAF a little clean up and I didn't have any problems again. I also noticed a lean exhaust smell when the engine was cold on my 4th gen. Did a few things with no luck. Just for maintenance reasons I replaced my fuel filter. I have the 300ZX filter that is suppose to last 30k, but it was filthy at just over 20k. Which is odd, because I always use 93 and fill my tank. I guess it could have been the couple bottles of Techron I ran through during that time. The car does have 180k. Sorry, tangent. All this to say, my cold-start lean problem went away following the filter change.