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Intermittent Idle issue

Started by fjbiker, May 06, 2013, 04:58:40 PM

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Pat Conlon

With the stock needles and 37.5 pilot jets on my '84 I found 3 turns to be best.
Actually, I like running the inboard #2 and #3 a tad bit richer, say 1/4 turn more (out) because they run a bit warmer than the outer #1 and #4 cylinders.
1) Free Owners Manual download:
2) Don't store your FJ with E10 fuel
3) Replace your old stock rubber brake lines.
4) Important items for the '84-87 FJ's:
Safety wire:
Fuel line:


Thanks everyone for all the suggestions. Here's the latest update:

Last night I checked the battery and charging voltages and I think things are ok here.
With the motor not being run for 24 hours, the battery measured 12.8 volts.
It measured 12.8 v at 1k rpm and a steady 14.2 volts @ 2k rpm and higher.

I also check to make sure that the throttle is returning all the way back and not getting caught or hung up.

Frank, Just like you suggested, I decided to go back to the original settings I had and work from there instead of starting from 2 turns-outs. I was content with the original performance. This was all just part of the trouble shooting process to find the cause of my intermittent idle stumble issue.
I settled on 3.5 turns out (originally ranged from 3.5 to 4.75). So I still ended up leaning the mixture out a bit.

I think I may have stumbled on something after I finished adjusting the fuel screws & checking the carb synchronization yet again. I started the motor one more time with the tank still off the bike, but I had forgotten to plug the fuel pump vacuum hose line.
The engine gave me the same idle drop and stutter symptoms I was experiencing when waiting at the lights. When I blocked the vacuum hose with my finger, the idle smoothed out and returned to normal.

I think I may have an intermittent vacuum leak.



Life isn't about having the best, but about making the best of what you have...

1990 FJ 1200