Off-Road Forums & Discussion Groups - View Single Post - misfire diagnosis w/ vacuum gauge
View Single Post
post #1 of (permalink) Old 07-03-2009, 10:31 AM Thread Starter
Tim-E
Journeyman
 
Tim-E's Avatar
 
Join Date: May 2007
Location: HHI SC
Posts: 117
Thanks: 0
Thanked 0 Times in 0 Posts
 
misfire diagnosis w/ vacuum gauge

Hi!

i was reading the junkyardgenius page on using a vacuum gauge to tune my carb, and some questions came up.

I've been using a vacuum gauge to try and get my mc2100, HEI 258 to run a bit smoother for me. She's got a random misfire that's been plaguing me for a couple of years.

Just at idle for example: it'll idle smooth, but every 5-10 seconds it'll have slight miss that I can hear in the exhuast....crawling in first gear gives me a rough, stumbling, surging....the same thing at most rpms, though its less pronounced at higher RPMS...

fuel pump is giving me 3 psi.
plugs are only a month old
HEI dist. is new
Idle is about 800rpm or so...
Timing set 8-9*

So heres my vacuum gauge questions:

1. when my gauge is not connected, the needle rests at at 7in HG, not 0. is that normal?

2. when i've got the gauge hooked up to the port on the rear of the intake manifold, i get about 24in HG at idle, but it fluctuates(vibrates) between 22.5" Hg and 24" Hg
Isn't this vacuum too high? what to do next? Retard the timing?

THANKS!
Tim
Tim-E is offline  
 
 
For the best viewing experience please update your browser to Google Chrome