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Unread 05-27-2015, 12:15 PM   #1
kcsnation
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1988 YJ Wrangler 
 
Join Date: May 2015
Location: JAMESTOWN, North Carolina
Posts: 17
Vacuum advance problems

i Had a post earlier about this, but cant seem to get a decent response. (No offense intended just figured I'd clear some things up)

Jeep has 258 with weber 32/36 carb and nutter bypass, timing is at 8 deg. Vacuum advance was disconnected when i got the jeep.

idle is still bad and Sputters/misses and is worse under load, (higher rpms are fine though) have adjusted carb but only partly fixes problem. (atmospheric changes throw the thing off i guessing)

When i hook the vacuum advance up to the carb (either ported or manifold) idle is fine and right. (i know why because that's its purpose) but when i get above 2000 rpms the advance does not drop off and throws timing of engine off.

Ive tried adjusting the advance but doesn't seem/feel like its doing anything. (might be broke) i do know that the arm is moving when vacuum is hooked up.

My question is why doesn't the vacuum pull off at higher rpms, and what can i do to fix this.


Thanks

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Unread 05-27-2015, 01:41 PM   #2
dancytron
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1990 YJ Wrangler 
 
Join Date: Jun 2008
Location: st. louis
Posts: 1,559
You need to really test it. Do you have a vacuum pump and timing light?

Use the pump to set different settings and see how much the timing advances. Then try to adjust it and see how it changes.

When I got mine, there was so much crap caked up on the arm that it barely moved. Maybe a good cleaning would help. If it is broken, then it needs to be replaced. . .
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Unread 05-27-2015, 08:34 PM   #3
kcsnation
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1988 YJ Wrangler 
 
Join Date: May 2015
Location: JAMESTOWN, North Carolina
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Im almost at the point of giving up on this thing. Replaced the distributor and advance today. The weber ports for the egr or vacuum advance do not give enough vacuum at idle to advance. Only thing that does is manifold vacuum. At high rpms timing is off (starts at 2000). Now question is what do i need to do to the advance to get it to work right. Adjust clockwise or counterclockwise. I really don't know what to do here at this point.
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Unread Yesterday, 04:09 AM   #4
Mike Romain
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Quote:
Originally Posted by kcsnation View Post
Im almost at the point of giving up on this thing. Replaced the distributor and advance today. The weber ports for the egr or vacuum advance do not give enough vacuum at idle to advance. Only thing that does is manifold vacuum. At high rpms timing is off (starts at 2000). Now question is what do i need to do to the advance to get it to work right. Adjust clockwise or counterclockwise. I really don't know what to do here at this point.
It "is" working right.... At idle, you should have 0 timing advance using the ported nipples. Then when you get on the gas, the timing jumps up real fast.
If you use manifold vacuum, you get full vacuum advance at idle, then when you give it gas, the timing takes a dive. Some folks prefer it this way for the slow smooth take off. I personally prefer ported vacuum, plus that is what the emissions sniffer likes.
You do not need o mess inside the distributor. That is for pro tuners and racing engines, the stock setup work great for normal use.
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Unread Yesterday, 04:29 AM   #5
jimbos76cj
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1989 YJ Wrangler 
 
Join Date: Jun 2007
Location: Florida
Posts: 461
I did a lot of reading on this the other night and come to find out I was a wee bit wrong on my advice (don't hear the often do you)

Did you ever say if the Nutter bypass was done on yours? If it's done and all your emissions crap is void you should be running it at 8-10 of timing with your vacuum on a manifold source and here's why. On start up more advanced timing makes it harder for the motor to start so manifold doesn't build idle until the jeepf motor is running. So with a base of 8-10 once it started your vacuum pulls up to 16-20 (should) giving the motor a smoother idle, run cooler and have more power. The higher advance timing doesn't effect the motor because it's not under load. When you step on the gas the motor goes under load and if some timing doesn't pull out you begin to detonate. The vacuum advance on manifold will dive off to prevent this. When you get to cruising speed most of the vacuum returns allowing the timing to go back up and increase effiecency.

On smog cars the base timing will be set lower or even after TDC to help gasses burn cleaner but the power is reduced. When hooked to ported as you apply the pedal vacuum begins to build and advance the timing to help build power.

Honestly I don't think your issue is with the distributor. I think you have a carb timing issue or some other problem.
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