Bought a 92 mpv 4wd with 75,000 miles. Love it! Had timing belt, leaky water pump, fuel filter, and all belts and hoses replaced. On cold start it idled way too fast. Up to 2400 rpm, then dropped to 1600, then back to 2400. It repeated this a half dozen times, than stayed at 2400 and slowly came down to normal idle. I had the intake manifold gaskets replaced. Now it does not ‘surge’, but still idles at over 2000 rpm for about 2 minutes on a cold start. Van has been to 2 Mazda dealers and 3 private garages. One replaced the ‘air temp sensor’, but no difference. It seems to me it must be some kind of temperature sensor, since it only does it when cold.
once it warms up for a bit the idle drops to normal levels?
The computer determines the engine idle at a cold start from the signal it gets from the engine coolant temp sensor. If the sensor has failed where it’s telling the computer the engine coolant is at -20?, it will cause the cold start idle speed to be too high.
Thank you very much for the quick responses. I love this van, but this high idle has been very frustrating for me.
It does idle down to normal idle speed, but it idles at 2400 for up to 2 minues. Funny thing- if the car is partway warm it does not idle ‘partway’ fast. It either idles at 2400 for 2 minutes, or at about 1500 for 15 or 20 seconds and then comes back to less than 1000, which I think is normal.
I know the last mechanic erplaced a temperature sensor- i will check my records and see exactly which one.
I live in northern AZ, so a ‘cold’ start here is 70 degree outdoor temperature right now. I’m worried about winter, when the morning outdoor temperature can be 30 degrees.