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Unread 05-21-2002, 05:49 PM   #1
CJ8DV8
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Sol-Vac solenoid problem

I just paid a fortune to get the '8 fixed (rebuilt BBD carb, repair intake manifold vacuum leak and replace rear main seal- $1100). When I got home I noticed that the vacuum hose to the sol-vac was disconnected and the vacuum hose was plugged. I know I had it hooked up before it went to the shop, so I hooked it back up.

Here's the problem: When the engine is warm and in drive, the idle surges - like someone is tapping the gas pedal. I immediately suspected the sol-vac (gee, could this be why it was disconnected?). I parked the front wheels against a curb and popped the hood. Sure enough - the sol-vac was pumping the throttle back and forth. I disconnected the wire to it and it was still doing the same thing. This means that the vacuum portion is at work when the problem happens. Of course, the vacuum hose runs to a computer controlled vacuum solenoid.

My thoughts: First, it didn't do it before I brought it to the shop. I should bring it back and have them fix it, but I don't want to have to pay any more. Second, why is the vac-sol surging? I would assume that if this thing was to activate it would stay on for a certain amount of time and not keep pumping back and forth like a horizontal pogo stick.

Any ideas???

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Unread 05-21-2002, 06:11 PM   #2
johny1i
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First off, make sure that you are aware of the purpose of the sol-vac, and that is to increase the engine's idle speed to compensate for a load on the engine. A load occurs during one of three occurences--the AC is turned on, the rear defroster is turned on, and/or the wheels are turned all the way right or left (assuming you have power steering, otherwise not a factor). Now, I'm assuming that on a CJ8, you don't even have AC or a defroster. Therefore, why even have the thing? I do have an AC on my 90, and the AC only drops the idle 150 rpm--hardly enough to worry about. Plus, my sol-vac had a similar problem--it would extend to speed up the idle when the AC was on, but then when I turned the AC off (or it cycled off), the sol-vac wouldn't disengage, which meant I had an idle of about 1100 rpm. My advice: scrap the sol-vac and plug the vacuum line that runs to it at its source. I did it four years ago and have never had a problem without it.
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Unread 05-21-2002, 07:07 PM   #3
Bob K
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Get rid of it along with all the other unnecessary plumbing. Here's what they do:

<a href="http://home.sprynet.com/~dale02/list.htm" target="_blank">http://home.sprynet.com/~dale02/list.htm</a>
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Unread 05-21-2002, 07:36 PM   #4
CJ8DV8
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I guess the shop had "getting rid of it" in mind when they disconnected and plugged the vacuum line. I wouldn't really mind leaving it that way except I spent alot of time trying to put the Jeep back the way AMC made it in the first place. I figured that they must have put it there for a reason.

Speaking of reasons- No, I don't have AC or a rear window defogger. I do have power steering, though. I also like the idea of it bumping up the idle under load situations, but if the only time the sol-vac will do anything for me is when I turn the wheel hard left or hard right maybe I'll have to go against AMC's reasoning afterall.

Its just that it seems that when the engine does die at idle it IS under a slight load situation and I wished it DID bump the idle up some.

Wishful thinking???
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Unread 05-22-2002, 03:08 PM   #5
CJ8DV8
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Johny1i (or anyone else that might know)-

You said that one reason the sol-vac operates is when the power steering puts a load on the engine. The other two were the rear window defogger and AC. I know that the AC and defogger are electrically operated systems and would most likely trigger the sol-vac elelctrically- either directly or indirectly via the computer/solenoid combo. In my case these are not applicable uses.

But how does the sol-vac know when to operate when the power steering pump puts the engine under load? I've never seen a wire tied into the power steering system - its purely hydraulic. Does the sol-vac or computer have some way of sensing the additional power steering load? I have some fat Mickey T's and its possible my stalling at idle is due to the power steering trying to turn them at slow parking speeds (always the case) with the sol-vac disconnected.

Can you enlighten me as to how this part of the system operates? I think I may have a flakey sensor and am trying to pinpoint it.

Thanks.
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Unread 05-22-2002, 05:55 PM   #6
johny1i
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I wish I had a specific answer for that, but I even pulled out my Chilton's book to check it out and all it says is that "the holding solenoid maintains the throttle position, while the vacuum actuator provides additional idle speed when accessories such as the the AC or defroster are in use ... The actuator is also activated when the steering wheel is turned to the full stop position." I've always been told that it's bad on your idler(?) arm to turn to full stop because of the stress that the hydraulics place on it, but that's just a general thing that my dad always said <img border="0" title="" alt="[Wink]" src="wink.gif" /> . Your dying-at-idle situation is peculiar in itself, and it doesn't make sense why the engine would die because of a load as minor as turning the wheel. How high is you idle? Mine is about 750 because I know it will drop to 600 with the AC on. I can sympathize with your decision to keep all of that stuff under the hood because of the money spent, but I can tell you that the number one reason I removed it all was because it was too difficult to track down vacuum leaks, etc. that seriously affect idle. I've got it whittled down now to the point that it can only be within 3-4 vacuum lines. Sorry I can't suggest more--I'd probably double-check the idle mixture and ignition timing just to make sure the engine is at optimum power.
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Unread 05-22-2002, 05:57 PM   #7
johny1i
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oops--by the way, there is no sensor on the power steering system.
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Unread 05-23-2002, 08:42 AM   #8
CJ8DV8
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Johny1i-

Thanks for the input. I agree with the vacuum leak problems you mentioned - looks like a bunch of snakes with all the vacuum hoses under the hood.

I think what I'm going to do is bring it back to the shop. It has to go back for an exhaust leak they caused anyway. I'll mention the disconnected sol-vac situation and let him have a look. I'll tell him if any repair is going to cost any more, then don't do it. I'll disconnect it then.

Thanks for your help.
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Half hardtop
Rustproof plywood floorboards and bed upgrade.
Lots of work, but working on it.
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