6.2 wont idle down

[rumpity_z28]

Hi there im having a problem with my truck and was wondering if anyone else has experienced the same problem.The truck is a 86 Silverado Chev with the 6.2 which has been great for me so far,but the other day when i was driving it the idle kicked up and wouldnt kick off even though the truck was up to temperature.So i unhooked the the high idle solenoid but then the truck was way noiser than normal,so i backed off the screw on the high idle solenoid and plugged it back in to quiet it down.But noooooo that didnt work now its always loud like it was when i first start it in the morning.The engine is new and only has 100,000kms on it and the pump was replaced just before the engine was done.the only maintenance ive done on the motor since installing it is regular oil changes and ive replaced the airfilter with a k&N.I had just started running some amsoil diesel stuff in my fuel just to clean things up abit.But thats the only thing ive done different since the motor was new.Any ideas?
PS this is a great sight!! smile.gif

[john8662]

Sounds like the temp sensor in the passenger side head has gone bad. The sensor is on the rear of the engine, passenger side. Its a two connector sensor, if this sensor is bad you'll get the results you describe. The reason why the engine is noisy is because the timing is also advanced by the same sensor that runs the fast idle solenoid. I'd check the the connector at the sensor to make sure the wires aren't crossing, otherwise you'll need another sensor.

[rumpity_z28]

Hi john thanx for the reply.I just went and checked under the hood and found the temp thing you were talking about.So whats the proper name for that cause theres one on the other head (drivers side) at the front that only has one wire.Are they the same?

[john8662]

Hmm, I don't have an exact name for that one, I replaced the one in my 86, but for opposite reasons. The sensor was completly and open circuit, never got the high idle or advance in the pump. I think its called the cold advance/idle sensor. The other sensor on the drivers side is the temp sensor for the gauge inside.

When you change that sensor, you'll want to have the new one in hand right as you remove the old one, otherwise you'll loose a bit of coolant. This sensor resides in the water passage in the head.

[rumpity_z28]

thanx john that fixed me right up truck runs like a dream again ;) the new switch even came with a new style connector so it wont fill up with valve cover oil. :D

[rumpity_z28]

Darn it went again thinks me has a short somewhere.It isnt possible to wire those up backwards is it?

[john8662]

Hmm, either you can't or I have always gotten lucky ;) I Don't think you can wire it backwards as you are right in that its a switch.

[Peter J. Bierman]

You might have a short further on in the circuit.
The sensor can only switch so much amps, drawing a lot more like in a short the sensor can burn.
Maybe one off the solenoids is shorting when it heats up, seen it before and is a pain to find. :mad:
Put a 10 amp fuse in the place off the sensor and switch on ignition and wait and see. :rolleyes:
If the fuse burns, put two fuses right in front off the soleniod connectors to see witch one is going bad.

;) Peter