This is a follow up to my earlier post regarding engine pinging when cold. I discovered today that when it is raining out or when we have high humidity the engine runs normal, no pinging. When the temperature drops and it is a relativly dry day the engine runs rough and pings at first until it warms up. So to sum it up...
COLD + DRY = PING.
COLD + WET = NO PING.
Would I be looking at a possible sensor problem and if so which one? The only sensors that come to mind that could be affected by the surounding temp/humidity would be the MAF or the O2 sensors. Any ideas? Thanks.

 

I think you may have overlooked two sensors most likely to be your problem.
1. Engine coolant temp (not the gague sensor)
2. Air charge temp sensor. (upper intake plenum)

Of the two, I would go for the ECT first. This one signals PCM when engine is sufficiently warm to enter closed loop operation. When engine is cold, it signals engine to run in open loop and default to pre=programmed rich operation till closed loop is signaled.

Air charge temp sensor is provides information on incomming air manifold charge temp. It is used to refine the fuel calculations.

Since you stated your (lean mixture) ping was mostly related to a cold temp, I would definately investigate these two. Air temp/density which is not properly measured or accounted for will cause the fuel/air calculations to be off.
Dialtone

 

I do know where the ECT sensor is, but where is the other sensor. BTW this is for a 2000 XLT w/4.0 SOHC engine. Thanks for the reply.