92 xj dies on idle when cold

[DaveB]

My 92 xj with the 4.0 has started to die on idle when it is cold. It only does it when it is first started (usually in the morning). The motor revs fine on first start but when the idle speed drops it dies. After the second start it is usually fine and after warming up it is fine.
I read a bunch of the older postings and most idle problems were on the older Renix systems or were fast idle issues.
I have spare injection parts and sensors, so where do I start first?
Also quite often I will have to put it in nuetral after the first start so I know I need to clean the NSS.
Thanks,
Dave

 

[Gray XJ]

Well you should clean your NSS first, then check the tps and cps sensors.

 

[Dr. Dyno]

If the NSS turns out to be OK, it's likely that the coolant temp. sensor (CTS) is shorting out. That's the one in the t'stat housing. This would cause it to give too low a resistance, the PCM thinks the engine's warm, and makes the A/F mixture too lean.
Check the wiring to the CTS and make sure the insulation isn't broken. If you have an ohmeter, back probe the two wires and measure the resistance across them when the engine's cold.