Mike Romain wrote:
> Usually a sick one will show in it's colour, like you describe your's
> showing a lean mix with their white ceramics.
>
> With a modified carb and rough idle I also think lean miss. How did you
> set up your idle mix screws?
Hi, Mike... I use the Lean Best Idle method described here:
http://www.redlineweber.com/html/Tech/carburetor_set_up_and_lean_best_.htm
But even if I fatten up the idle mixture considerable, I still get a
rough idle. I have read that a rough idle is common to this particular
version of the Dodge/Chrysler 3.9L V6.
Steve W's first reply in this thread speaks to the nature of this engine
that causes it to idle roughly:
"Let's see an 87 V-6 no balance shaft with a crankshaft that wasn't the
best design for smooth running. And it idles a bit rough.
YUP sounds 100% normal to me. Think of the way that engine runs. The
power pulses are not evenly spaced. Kind of like if you built a set of
stairs, with every third step 15" tall. Think it might affect the way
you run up them?"
Aside from that, I had one instance recently where I was getting a
comparatively stable idle as read by the tachometer function on a
digital meter. I prepared the vehicle up for setting the idle speed as
per the service manual. I used a digital meter and it fluctuated only
between 70 and 71. You have to multiply the display times 10. Usually,
it fluctuates between about 66 and 74.
For the life of me, I haven't been able to recreate that stability, but
it was not that long ago so the ignition parts are probable not the
reason. All indications point to the air/fuel condition.
I recently removed all vacuum hoses from the manifold vacuum and plugged
up all ****ts. This would be for the air switch relief valve, the heater
vent doors, purge solenoid bleed, vacuum kicker bleed for idle,
electronic spark advance and the rough idle seemed to continue. To be
sure, I should do it again and check with the tach meter.
>
> Mike
> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> 'New' frame in the works for '08. Some Canadian Bush Trip and Build
> Photos: http://mikeromainjeeptrips.shutterfly.com
>
> Simpson wrote:
>> I pose this question in my ongoing quest to improve performance on my
87
>> Dakota without spending unnecessarily.
>>
>> Actually, it's not the spending that bothers me. I just don't feel like
>> changing my plugs. Condemn me for a lazy good-for-nothing if you will,
>> but that's just the way it is today.
>>
>> The reason I know that they look healthy is that every once in a while
I
>> pull one to see how it's doing.
>>
>> Hello, plug
>> How ya doin'?
>> I come to watch your changing huin'
>>
>> (huin' - slangy contraction of 'hueing', from 'hue', a gradation or
>> variety of a color; tint)
>>
>> The plugs have nice, unworn, square electrodes and are properly gapped
>> and, over all, have a nice healthy appearance, albeit the ceramic
>> insulators are a bit on the white side. Can I assume that they are in
>> good shape? Or is there some internal condition, unseen by mortal eye,
>> that can develop, that causes plug performance to deteriorate?
>>
>> The truck idles a bit rough, nothing at all severe, but something that
I
>> think could be improved. I am ruling out the fuel delivery for the
>> moment and concentrating on the ignition. The cap and rotor appear to
be
>> in good condition. The ignition wires all measure a bit below the low
>> end of the resistance range as specified in the service manual, 250 to
>> 600 ohms per inch. Mine are about 200 to 220 ohms per inch and are not
>> that old.
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