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Volvo 740 Temp Gauge pegged

Howdy,

87 740 GLE. Had an idle oscilation problem. After reading the comments here, replaced the flametrap, cleaned the throttle body, idle control valve, and assosciated hoses. She is running much better. Thanks!

But... The temperature guage is now pegged. Which after reading the brickboard FAQ, I think means I managed to disconnected the sensor wire. right?

I took notes, and everything I took apart _intentionally_ is back together.

Any reccomendations on how to start troubleshooting this?

I am guessing I need to take the idler control valve and its hose back off and take a look under the manifold for the temperature sensor and its wiring. It is under there right?

Who else here has done this accidentally and what was the fix?

-Thanks in Advance

-Matt

Reply to
psyshrike
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I wonder if you disturbed a wire in your efforts to deal with the flame trap. Older Volvo's have weak insulation around the engine wiring.

Reply to
Ric

You are correct in the location of the engine temp sensor. Low resistance = hot, so as suggested you've jostled the remaining insulation off the wires leading to it, shorting them out. You can see it from above, close the the runner for cylinder #3. Keep in mind this won't be the only place the insulation on this harness is bad. You can tape up the harness by removing the intake manifold, it's not too difficult, but if you're the kind of person that frustrates easily, get someone else to do this. If you do attempt this, the only gotcha is the connectors for the idle valve and throttle switch can be interchanged, and if you do, it kills a transistor in the idle circuit inside the computer, so make sure you mark which is which before you start!

Reply to
Mike F

Thanks for the heads up on switching the wires. Hope you didn't learn that the hard way.

You guys were right. The insulation was completely gone from the wires about 2 inches back from the sensor. I was able to degrease them and get my fingers in there to tape them up after disconnecting the idler valve.

Kindof a bodge job. I'll take off the manifold and do it right when I get around to sending the injectors out to be cleaned.

-Thanks!

-Matt

Reply to
psyshrike

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