Rough idle with vacuum advance -
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post #1 of 1 Old 08-23-2019, 05:03 PM Thread Starter
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1983 CJ7 
Join Date: Oct 2018
Location: Raleigh
Posts: 27
Rough idle with manifold vacuum advance connected

Hi all,

I have a 258 with a Sniper EFI conversion that I finished late last year. Everything else is pretty much stock and I've had the Jeep about a year. During that time, I've driven it about 300 miles, and it runs and idles pretty good since the EFI conversion.

Last week I began replacing some old vacuum lines with new ones. In doing so I discovered that there was a BB in the distributor vac advance line the whole time I've had it, so I've been getting no vacuum advance, only mechanical. I recently put in the new line and have it hooked directly to manifold vacuum, as it was before (but was blocked off by the BB). When I started it up after putting the new line on I noticed it began to idle rough as it started to warm up. I drove around less than 5 miles and it almost died on me a couple of times, which it didn't do before. In the days after, I checked the vac advance on the distributor with a vacuum pump to confirm no leaks and it does advance with the handheld vacuum pump.

With everything hooked back up I ran it again today, and the same thing happened - rough idle as it began to warm up, and continued to do so long after reaching normal operating temp. Thinking about how it idled fine with no vacuum advance before, I plugged the manifold and distributor like you would when setting the initial timing (which is 8* BTDC). I cranked the Jeep back up and it idled fine once again and drove the way it did before putting the new vac line on. Any ideas what could be going on here? Runs fine on no vac advance, runs rough on full manifold vac.

1983 CJ-7 / 258 / T4 / 32" BFG mud terrains
Wolfpack83 is offline  

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