So... Recently while driving to work I looked down at my coolant temperature gauge on my 1990 Pickup 22re, and it was jumping quickly between about half way to completely cold. Later I also noticed while parked at a stop light my tachometer was jumping very erratically between ~400, ~1200, and ~1500. I think somehow these are connected and there's something wrong with my autochoke. Has anyone else had this problem? and how do I fix it? Thanks

 

This is a copy from my 88 build. Had the same problem with water temp gauage. Not sure about tach problem.
A while back I was mentioning that my wifes truck water temp guage was going from half way to cold. I actually forgot about it until I drove it today and it did it again. I pulled the water temp sensor and it had green corrosion on the sensor cleaned them with a brass wire brush and then I cleaned the contacts that goes to the wire as well with electrical contact cleaner. No more problems. Stays just below half as it usually does. I knew it wasnt overheating, but still like having a guage.

Here is a picture of a dirty Temperture Sensor. I have seen worse. I chipped some of the scale build up off so you could see a difference.


The sensor sits just below the Cold Start Injector in the Intake manifold. Uses a 17mm deepwell socket and is a 5 minute job.