Very high idle

Hi guys pretty new to this stuff but I have recently replaced the motor on my 92 b2600 first thing in the morning it will start fine but idle at 2800 rpm and when it is warm it will not start at all has anyone had this problem or have any ideas on a fix? Cheers

http://www.mazdabscene.com/threads/35537 Start there. It sounds like you have a bad coolant temperature switch. Maybe the plug has corrosion on it. Fuel injected vehicles don't have chokes. Will the truck start if you floor the throttle?

I will try but I reckon it does have a manual choke and I'll replace the coolant temperature switch and let you know how it goes Thanks

1992 B2600 are fuel injection motors. Why do you have a choke?!

Not sure but definitely has one wouldn't have thought that being fuel injected it would even need one but hopefully the coolant temperature switch fixes it lol

Did this happen ar same time of engine install? Is the accelerator cable caught on something.

Yes old motor never had this problem I checked the accelerator cable and it wasn't caught on any thing would incorrect timing make it idle to high?

Yes it could. Post some pictures.

Replaced the coolant temp sensor it only it still doesn't start all the time but when it does start it will idle normally untill it starts getting hot then will creep up again

 by 91_2600i over a year ago

There is an idle air control valve on the top of the throttle that regulates idle air - as it warms up, it allows less air to "Bypass" the throttle. In fact, Mazda calls it a Bypass valve. Yours is probably stuck wide open. They get gummed up over the years and will tend to stick.


You can test each of the those two parts, but even if each tests OK doesn't guarantee that they're are not faulty.


IAC Valve:


Disconnect ISC valve electrical connector. Connect ohmmeter to ISC valve 2-wire connector. Measure resistance. See ISC RESISTANCE SPECIFICATIONS table. If resistance is not within specification, replace ISC valve.

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