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Weird idle fluctuation
https://www.slantsix.org/forum/viewtopic.php?t=47945		 Page 1 of 1
Author:  raPoM [ Sat Feb 18, 2012 9:20 pm ]
Post subject:  Weird idle fluctuation
Just got done installing my 4bbl,and have a strange issue. This is for my 87 D100,and the lean burn is still controlling the timing.The carb is an eddy 500 performer,vac secondaries and electric choke.

Got everything hooked up,hit the starter a few time to get fuel in the bowl,pulled the throttle once and hit the key,it fires up instantly.

Here is the weird part: The idle shot way up to about 3,000 rpm,and would fluctuate between 1,000-3,000 rpm :shock: THis is not like a vacuum leak, not a slight surge up and down a few hundred rpm,but a few thousand RPM. Also,at one point it idled down to 1200 rpm(with choke on,like a fast idle) and was steady for a bit. This is also why I dont think it is vacuum related.

My idea is that without all the LB stuff hooked up,the computer is going bat $#!+ and advancing and retarding the timing like crazy to make up for it.

I read the LB conversion article,and followed it closely. It didnt mention anything about what to do with all of the vacuum lines,does one or more need to be hooked up for it to run right?

Thanks for any help/ideas
Jared

PS- When it was idling normal,I hit the throttle and this thing is snappy :twisted: cant wait to get this figured out,should be a hoot on the street.
Author:  SlantSixDan [ Sat Feb 18, 2012 9:43 pm ]
Post subject: 
I think this problem is because you haven't spent enough time in church. Read your Bible; it says not to worship false idles.

Image

No, srsly: hook up a timing light and see what's happening with the timing, but you're not going to get 3krpm or even a 2krpm or anything near it simply by dint of timing. There is something messed up with your carburetion.
Quote:
It didnt mention anything about what to do with all of the vacuum lines
All what vacuum lines, specifically?
Author:  raPoM [ Sat Feb 18, 2012 10:01 pm ]
Post subject: 
Hahaha myabe :wink:

Im talking about all of the LB associated vacuum lines. I have the lines for the charcoal canister hooked up,but all other vacuum lines are unplugged.

What is weird to me is how it all the sudden ran ok,and the idle stopped fluctuating. That is why I didnt think it was the carb. I will stick a timing light on it tomorrow,and see what its doing.
Author:  SlantSixDan [ Sat Feb 18, 2012 10:12 pm ]
Post subject: 
There aren't many vacuum lines associated with the lean burn setup. In fact, there is pretty much only one, supplying manifold vacuum to the lean burn computer. That one needs to be hooked up. Soooo...what are all these other lines you've disconnected?
Author:  raPoM [ Sat Feb 18, 2012 10:16 pm ]
Post subject: 
I will snap a picture tomorrow. There are about 4-5 vacuum lines disconnected right now. It looks like they lead to something over on the passenger side inner fender. I will trace the computer vac line,and make sure I have the right one hooked up tomorrow. Im beat.
Author:  Joshie225 [ Sun Feb 19, 2012 12:06 am ]
Post subject: 
An idle fluctuation that large would lead me to pull the carburetor and examine it closely. I would make sure the primary and secondary throttles are closing properly. I would also be checking for vacuum leaks between the carburetor and it's adapter, the adapter and manifold, the manifold and cylinder head.
Author:  raPoM [ Sun Feb 19, 2012 4:04 pm ]
Post subject: 
Well,it was the carb base gasket. I used the cheapy one that came with my eddy. I replaced it with a thicker one that I had,and walla it ran great..... until I went for a test drive,and shot the number 5 rod at 3500 rpm in 2nd. :x

Im kinda screwed now,looking for a replacement motor. What a weekend.
Author:  SlantSixDan [ Sun Feb 19, 2012 4:38 pm ]
Post subject: 
Quote:
Well,it was the carb base gasket. I used the cheapy one that came with my eddy. I replaced it with a thicker one that I had,and walla it ran great..... until I went for a test drive,and shot the number 5 rod at 3500 rpm in 2nd
Aw, geeze. One step forward, three steps back. Sorry to read it, man.

Check craigslist and www.car-part.com for a replacement engine.
Author:  raPoM [ Sun Feb 19, 2012 4:49 pm ]
Post subject: 
Thank you,its my fault. I need to stop trying to hot rod my daily driver. Once i gett the 4bbl sold,and new short block I will be hitting you up for a new 1945. Im just going to keep it stock. Im a broke ass college kid,and really cant aford this.
Author:  raPoM [ Sun Feb 19, 2012 5:03 pm ]
Post subject: 
Found out a good friend of mine has a short block that I can use :D Im heading over there tomorrow after school,and swapping it in. Im going to sell my 4bbl stuff,and get my head rebuilt,and just buy a 1bbl and install my HEI and drive it. No more treating it like a race car :lol:

Finally some good news! I feel better. :D
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