Idle Air Control Valve question

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nonenino68
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Idle Air Control Valve question

Postby nonenino68 » Tue Jan 06, 2009 1:52 am

Hello to all of you and happy new year. My 94 850(non turbo), does not start after sitting in the garage for 2 days. No symptoms prior to that. I turn the key, the starter engages but the engine does not engage. I check the trouble codes and I get a 2 2 3, which indicates idle air control valve signal absent or faulty. Would the iac valve cause the car not to start all of the sudden without causing some rough idling or stalling previously? This is the only trouble code I got. Timing belt is intact. I can hear the fuel pump and there is smell of fule when I try to start the car. Should I rule out a faulty ignition coil as well? Do I need to get a code to suspect a faulty camshaft position sensor? I wanted to know you opinion before I shell out $$$$ for the IAC valve. Thanks for your time and expertise as always!

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chuckcintron
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Re: Idle Air Control Valve question

Postby chuckcintron » Tue Jan 06, 2009 2:27 am

Yes, it can cause a no-start. With the key in the 'on' position (pre-start) you should hear the IACV buzzing away underneath the shroud that covers the throttle body linkage. No buzzing sound means it's time for a new one.

Check the wiring first, just to make sure nothing is broken or corroded.

-Chuck

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Re: Idle Air Control Valve question

Postby Ozark Lee » Tue Jan 06, 2009 3:18 am

I turn the key, the starter engages but the engine does not engage.


Do you mean the engine doesn't turn over at all? If so, that sounds like a Bendix problem to me.

...Lee
'94 850 N/A 5 speed
'96 Platinum Edition Turbo
'98 S70 T5
'99 V70XC - RIP - Wrecked Parts Car.
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nonenino68
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Re: Idle Air Control Valve question

Postby nonenino68 » Tue Jan 06, 2009 10:09 am

Thanks for the reply, when I turn the key, I can hear the IAC humming continuosly until I turn the ignition off. Is that normal? When I try to start the car, I can hear the starter, but the engine does not catch on, almost as when you have a low battery. I recharged the battery and tried a different battery as well. The weird thing is the car was running fine until last Friday night when we parked it. Pardon my ignorance Lee, but what is the bendix? Sorry, thanks again!

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chuckcintron
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Re: Idle Air Control Valve question

Postby chuckcintron » Tue Jan 06, 2009 1:19 pm

IAC humming (or buzzing) is normal, yes. Odd that you got that code, however. I'd carefully examine the connections at the throttle body, just to be sure.

The Bendix is an engagement gear that mechanically connects the starter motor with the flywheel when the starter motor is energized. There's a centrifugal spring inside it that, if breaks, will cause the starter motor to simply spin away without meshing with the flywheel to turn over the engine.

If this is your problem when you turn the key to 'start' you would hear the starter motor whine at a high pitch, with no engagement of the flywheel.

When you try to start your car is that what you are getting, or is the engine actually turning over?

-Chuck

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Re: Idle Air Control Valve question

Postby nonenino68 » Tue Jan 06, 2009 4:03 pm

Thanks for the reply chuck, after you explained it, I remembered. The engine is turning when I turn the key, however is not starting. I know that high pitched noise when the starter tooth is not engaging with the flywheel but that's not the case now. a neighboor and me just checked the coil and there is a spark. I used to have a 740 and I remember being told about cheking the flame trap. Does the 850 has one? I don't know where it is. Could a clogged flame trap be the cause for the no start? I'm thinking it may be a fuel delivery issue? I recently changed the fuel pressure relay(green one) and it has a relatively new fuel filter. Should I check the fuel pressure regulator? Thanks for your time!

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chuckcintron
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Re: Idle Air Control Valve question

Postby chuckcintron » Tue Jan 06, 2009 5:01 pm

I'm not aware that the flame trap would cause a non-start, but admittedly a bit outside my area of familiarity. Someone else might comment.

I documented a series of typical troubleshooting steps for a non-start condition in this thread...you might want to scan through it to see if it can help. Fuel pressure & volume at the rail is certainly something you want to validate.

Halfway down this page:

viewtopic.php?f=1&t=18098&start=20

-Chuck

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Re: Idle Air Control Valve question

Postby nonenino68 » Tue Jan 06, 2009 6:16 pm

Do I need to have a trouble code confirming a problem with either the crankshaft position sensor or the camshaft position sensor? Alot of the problems I've read about these two sensors is with intermitent no starting followed by starting after 10-15 min., however in my case, the car just doesn't start period. Is there any way I can test thses 2 sensors, before blindly replacing them? Thanks!

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Re: Idle Air Control Valve question

Postby chuckcintron » Tue Jan 06, 2009 7:52 pm

Crank sensor failure is very rare, but I would imagine should throw a code...zero output to the tach sort of thing.

Cam sensor is more common, and you'll usually get a misfire code.

I'm sure there is a test procedure for both, but I don't have VADIS so I can't tell you what it is. The cam sensor is a hall device so there must be a published resistance range for it.

I agree, I'd hate to toss a $160+ part at the car without knowing for sure the sensor is bad.

-Chuck

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Re: Idle Air Control Valve question

Postby nonenino68 » Wed Jan 07, 2009 2:37 am

Hello again Chuck. Here's were I'm standing with the car. A friend mechanic who is helping me spent the day troubleshooting and we have come to the conclusion that the timing is off, although the belt is intact. we changed the crank position sensor($57, not bad), distributor cap, rotor and spark plugs. In the process of cleaning, discovered the fule flame trap(it was full of gunk and dirt), replaced the flame trap and cleaned the IAC valve. The spark is now coming from the coil to the spark plugs, so there is a better current now. However the car still won't start. Checking out the timing belt, he noticed the bottom pulley is aligned as it should however the top pulleys don't seem to be aligned as shown by the book. We will resume working in the car between friday and saturday to tackle the timing issue. I really hope is just the timing now after a whole day of work in the car. I also found a place on ebay that sells the ignition trigger part of the camshaft position sensor which can be replaced on the metal assembly of the part. I'll keep you posted with the timing issue. Thanks for your help!


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