Nissan Repair: 1991 Nissan Maxima bouncing RPM, nissan maxima, maf sensor

Question
I have '91 Maxima and have a problem no one seems to be able to solve. When the engine is relatively cold, it hesitates violently and will not exceed 2000 RPM regardless of how far I press the accelerator. When I put in neutral and give it gas, the RPM's jump violently back and forth between about 1500 and 2000 rpm. The dealer says no codes show up. They replaced the Ignigtion control module and nothing, I just cleaned the MAF sensor and nothing. After about 6 hours of diagnostics, the dealer then told me the got a code that said the distributor was bad. I replaced it with a used distributor from a junkyard. Still nothing. Once it finally warms up, it seems to run fine, which makes me think it is some sort of thermostat issue, but not sure what/where to look. Any suggestion? Thanks!

Answer
Brian,

The problem seems to be related to being cold so I would think the cold temperature sensor is defective and the thing thinks it is warm and it runs bad until warm.  I would replace the temperature switch for the computer first.  Also, if the temperature is not running at 180 degrees I would change the thermostat to help it get to temperature faster.