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seasun7

idle not stable

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seasun7

I have a response monsoon 320 MPI.

when the motor is cold the idle rpm is stable at 1000.

as soon as the motor is warm the idle is not stable going from 500 to 1200 rpm.

I changed IAC, CAP, ROTOR, spark plugs, plugs wire.

checked compression, fuel pressure, firing sequence, advance.

I'am lost and there is no diag machine around.

Help !!!!!

Adam

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Hman442

There is a coolant temp sensor that tells the ecm the water temp. It could be the problem & is cheap & easy to replace. It should be a two wire sensor in the intake manifold. Take is out & take it to NAPA, etc. Have them look one up for an early '90s pickup & then look in their "picture book" to see if it is the same. Another possibility is the throttle position sensor at the base of the throttle body. I'm not certain if it is common with a GM product - but I bet it is. On some applications, these just bolt on, on others, they have to be adjusted properly after installation.

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seasun7

Thank Lance

there is no "two wire sensor" just single wire and when I plug it out and in or short cut to ground absolutly no effect on the RPM. Normaly does it should do something to the RPM ?

Adam

There is a coolant temp sensor that tells the ecm the water temp. It could be the problem & is cheap & easy to replace. It should be a two wire sensor in the intake manifold. Take is out & take it to NAPA, etc. Have them look one up for an early '90s pickup & then look in their "picture book" to see if it is the same. Another possibility is the throttle position sensor at the base of the throttle body. I'm not certain if it is common with a GM product - but I bet it is. On some applications, these just bolt on, on others, they have to be adjusted properly after installation.

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electricjohn

There has to be a coolant tempiture sensor. Check the front of the engine also.

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seasun7
There has to be a coolant tempiture sensor. Check the front of the engine also.

in fact there is 2 one for the dash board one for the ECM but this is one wire sensor and hman says 2 wires sensor.

What I want to know is when you plug or unplug the coolant sensor when the engine is warm, does it change the RPM ? because at the moment it has no effect at all.

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