Chrysler Repair: 2.5L V-6 runs rough when cold, chrysler cirrus, coolant temp

Question
my 98 chrysler cirrus with a 2.5 v6 runs rough when engine is cold, after it warms up it runs fine. it had a code p0302 cyl. 2 misfire on thursday and i cleared it. the check engine light is not on now though. do you have any suggestions?

Answer
Hi Kory,
The mixture needs to be adjusted for the temperature condition of the engine and the intake manifold. That adjustment is done by two temperature sensors whose resistance decreases as the temperature rises. The most important one is the engine coolant temp sensor located immediately to the rear of the coolant filler cap and just to the left of the air intake ribbed tubing (directions as seen from standing in front of the vehicle). It has a 2-wire plug with a tab to lift gently inorder to release it from the sensor (wires are green/white and black/green). When the engine is cold (77F) the resistance should read 9-11,000 ohms. When the engine is at operating temerature (212F) it should read 600-800 ohms.
The intake manifold sensor is at the other end of the engine, rear corner of the manifold (left end of the engine as you look from front) and it too has two wires (brown/blue and black/green) and a lift tab. It has the same temperature resistance characteristics.
Most important would be the resistances when cold. If they are much lower than the values stated, then the mixture will be too lean which would cause rough idling when cold. The resistance should decrease smoothly as the engine warms up. Of course if you disconnect the sensor while the engien is running that will also modify things, so stop the engine to measure the resistance as it warms.
The rough idling is causing the fault code; and because this seems to be temperature dependent these sensors would be where I would start. If you need to replace either, they simply unscrew. You will need to use a little sealant (loctite 24200 or equilent on the threads) and tighten gently to a very low torque, only 5 foot-pounds so be careful not to overtighten and strip the threads.
If those sensors turn out o.k., then we will have to look into some other possibilities.
Roland