Toyota Repair: engine, coolant level, coolant leak


Question
hi, i have a 1990 toyota 4-runner and its been a good truck , had the timing chaingn replaced last year and my truck has about 160,000 miles on it . lately when i start it to warm it up ,it starts with a high idle and then goes down which is normal, but then now it starts to surge up and down ,up and down and keeps doing that for awhile . do you have an ideal how to fix this ?

Answer
There are two possible conditions that I know of, the coolant level is low(check for a coolant leak)I can't go into the technical aspect of why this is, just take my word for it. The  less likely cause may be the temperature sensor for the ECU, it's located in the back on top in the middle of the engine along with some other sensors, I don't have access to a manual right now so try to have the toyota dealer show you on their computer where it is, remember that it is the temp sensor for the ECU, not the one for the temp gauge in the dash.