Hey guys! New to the forum, but long time Volvo owner. I've got a problem with my 1986 740GLE. I keep reading that the Idle Air Control Valve is supposed to have 12volt power on the middle wire of the 3-wire connector, but when I run a test light on my car, I see 12volts at both outside terminals. This is causing my control valve to not work at all. I've bypassed the problem by jumping the terminals and forcing the valve closed and adjusting the idle at the throttle body. Any ideas what could be causing this?

Edit: The engine is a B230F fuel injected non turbo.

Thanks!

Mark

 

No one has any ideas or at least can verify that what I said about the wiring for the idle control valve is true (center terminal should have 12volts)?

I really need some help.

 

All my info is for the 240 but I'm pretty sure you have the same LH 2.2 system, see attched. It shows the center wire being 12v.

[IMG]local://upfiles/15703/0585A78827EE4C6A8DC2B253829E8AE5.jpg[/IMG]

 

Thanks for the diagram. All the ones I have don't say the middle wire is supposed to have 12volts in the center. I either have a cross short in the wires or the ECU is bad. It just seems weird the only that part of the car is affected. You would think if the ECU is bad, the car wouldn't run.

 

Bad ECU's do many different things on these cars.

 

This is true. I guess what I'll do is swap the ECU and maybe even the LH Jetronic Relay (Fuel Pump). I checked another wiring diagram and it seems that the CIS valve is wired into that relay with the O2 sensor.

 

While I'm at here is a pic of the car we're talking about here

[IMG]local://upfiles/19320/60BD46ABDC0849A5931E595667C3FFF9.jpg[/IMG]

 

Make note of "H" in that diagram - its the throttle position switch that sits off the throttle body. It tells the ECU to control the idle valve when in the idle position. Also note the 3-pin connector for the TPS is the same size as on the idle valve, so sometimes they accidently get swapped, check wire colors.

 

I thought i may have swapped the connectors but if you swap the connectors the car won't start (I tried), but I'll verify the wires colors. I really dont think I have a cross short in these wires,I recently took the engine out and took the harness covering off and inspected all the wires for damage and didn't see any.

 

Maybe ohm out the TPS to make sure its returning to the "closed" position (with power disconnected)... and check to ECU connector for a good connection.

 

That is a nice looking car.

 

yea it's beautiful.

what symptoms did the car have (out of curiosity) when the idle air control valve wasnt working?

 

Well what happened to me is that I replaced the idle valve since I figured that was the problem. After replacement, the car would idle fast... real fast. Like 2500 rpm fast. So I tried to ground out the ICV at the test point to close it and she wouldnt close. So I then took the valve off and bench tested it with a DC inverter. Works fine when you apply 12volts to the center pin and ground one of the ends. I then tested the plug for the valve and found that there is not any power on the center postion, thus why the valve isn't closing or opening. So i grounded out the vavle and shut it until i can figure whats wrong with the car. In the meantime, i adjused the ilde at the throttle body and idle air bleed control ****. I belive my problem is in the computer, but do yourself a favor and test the control valve to make sure. It may be sticking and causing your issues. Or it could be bad.

 

Thank you! This is actually my first car i've ever owned. I've had it for about 9 years now and has 197,000 miles on the clock. Still drive her everyday to work approximately 100 miles round trip.