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Unread 05-13-2013, 08:44 PM   #1
Hondaracer2oo4
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1987 258ci wont idle

I am working on an 87 258 for a buddy of mine. I mostly work on motorcycles and small engine stuff so this engine is a bit foreign to me. The complaint was that the whole time my buddy has owned the jeep it wouldn't idle. So first things first I drained the fuel and replaced it with fresh fuel. Second thing I did was remove the carb(which is some sort of aftermarket carb, not a webber though) and clean it. Next I did the Nutter bypass which seemed to smooth out the high idle and made the jeep run much better while driving it around, except for at idle and when you let off the gas slowing down it just dies. Next I attempted to set the timing. I painted a white mark on the balancer and a white mark at 8 degrees for reference. Well the timing mark moves all over the place. It moves anywhere from past 20 degrees to well before -2 degrees and anywhere in between. The wires are not crossed or touch so I shouldn't have any cross contamination. My question is where should I start looking for the problem with the timing moving all over the place?

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Unread 05-13-2013, 08:49 PM   #2
Michaelgoesrawr
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When my timing was off like that it was the after market ICM fighting with the distributor advance.
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Unread 05-13-2013, 08:58 PM   #3
Hondaracer2oo4
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Thanks for the tip. This appears to have the stock ICM in place though.
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Unread 05-13-2013, 08:59 PM   #4
superj
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I would get a vacuum gauge and check what you pulling. It could be a vacuum leak as that is the description you are giving.

High idle and no low idle ability are a good vacuum leak somewhere. I would bet under the adapter for the carb
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Unread 05-13-2013, 09:07 PM   #5
Hondaracer2oo4
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Thanks for the tip, this thing has vacuum lines going EVERYWHERE! Anyway to eliminate some of these things? Which one under the carb? Where does it head to after the carb? This shouldn't cause the timing to jump all around though?
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Unread 05-13-2013, 09:12 PM   #6
superj
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Shouldn't but get it idling before worrying about that. I would unhook all the vacuum lines and cap them while you try to fin the leak. Usually, the adapters for after market carbs cause a lot of issues so pull that off and put a thin layer of some kind of sealant between the adapter and intake and a new gasket under the carb. That usually fixes and leaks at that spot. You can find the leak with some spray though by just spraying little by little around the carb and adapter and then the intake. The idle will go up or down once you find the leak, depending on what you use as a spray. Water in a little squirt bottle will make the idle drop while most flammable sprays in a can will raise it a hair. You will know when you hit the spot though
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Unread 05-13-2013, 09:16 PM   #7
Hondaracer2oo4
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Any suggestions on size of hoses to use if I were to replace all of them? They look to be a couple different size lines. I might as well just go around and replace everything to eliminate them as possible sources of leaks.
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Unread 05-13-2013, 10:00 PM   #8
Chrisnvegas
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nevermind, it has the nutter done to it.
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Unread 05-14-2013, 11:30 AM   #9
Hondaracer2oo4
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I checked on that vacuum hose under the carb that goes to the control for possibly the butterfly for the choke. It was cracked and leaking. I replaced it. Seemed to smooth out a tiny bit at idle but still has an obvious miss. I think something is up with the distributor being worn maybe? It has 97xxx original miles on it. Looks like most people say that they timing set will go 150000 before needing to be replaced so I would think that the distributor is the likely culprit for this timing mark jumping around.
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Unread 05-14-2013, 05:49 PM   #10
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Replaced distributor and coil today. No change in the timing mark moving around. I did find that the flywheel can be moved quite a bit in either direction before it moves the distributor. Thinking that the timing set is well worn out. Would this be a possibly culprit of the timing mark moving around?
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Unread 05-15-2013, 08:48 AM   #11
zeus87gn
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Check for manifold vacuum leaks at the head
The original manifold bolts have a tendancy to loosen over time
Also, most of the vacuum lines on the engine can be removed since the bypass has been done
I hope you changed the cam gear on the dist with the original one from the old dist too
Once you get the vacuum leaks handled, set up the timing for manifold vacuum and get a good tune on the carb
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Unread 05-15-2013, 09:39 AM   #12
Hondaracer2oo4
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Thanks for the tips. I did not change the old cam gear over to the new one. I guess I could easy enough. Why the change though? Also everyone seems to be glazing over the fact that the timing mark jumps all around and I can't get it to stop moving. I think this may be the culprit of the rough idle, am I wrong? The motor runs real smooth when you wind it up but when its down near 700-1000 rpm you can hear in the exhaust what sounds like a miss from the motor. Sounds like a tick every few seconds.
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Unread 05-15-2013, 10:36 AM   #13
zeus87gn
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Vacuum leaks will make the timing mark jump around
The timing chain will too, but not to the extent that you have described

The cam gear trick keeps the camshaft from wearing into a new dist gear
If you can keep the orientation the same it would be of help
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Unread 05-15-2013, 10:51 AM   #14
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Could be several things, so start w/ the basics.

Have you verified that your timing marks/pointer are in the correct spot? 0 should align w/ the pointer when the #1 cylinder is at TDC....if not, your balancer may have slipped.

Are you setting the base timing w/ the vacuum advance unplugged & capped?

Is the mechanical advance functioning correctly? You should be able to slightly rotate the distributor rotor w/ the cap off & have it quickly snap back (no slop). I've seen broken springs cause crazy timing readings.
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Unread 05-15-2013, 08:38 PM   #15
Hondaracer2oo4
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Ok Zues, that makes sense. I will swap out the old cam gear with the new distributor.

Beachcruiser, no I have not verified that the timing mark on the balancer is actually TDC of #1. Thats easy enough to do though, I will tackle that tomorrow.

No I was not setting the base timing with the with the vacuum line unplugged and capped. Pinching it off with some vice grips should suffice, correct?

Like I said some of this stuff is new territory for me, what do you mean by mechanical advance? The distributor is brand new.

Can someone explain to me how a vacuum leak would cause the timing mark to jump around? Thanks!
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