I have tried several different brands of caps and rotors. I have replaced
the spark plugs 3 times. I have replaced the spark plug wirers twice. I have
been very careful about the routing of the wires making sure there is no
It acts up worse on rainy or damp days. It won't miss to much for about 10
miles, then it miss very bad. Then I can shut it off for an hour, start back
up and it will run better(not prefect). The bad caps have a burnt spot in
the center of the cap. It looks like rotor is shorting out to spot where I
think the # 4 cyl trace is made into the cap.
I was thinking that the PCV valve might be pulling a slight amount of moist
air thought the distributor. I do not know if the shaft seals go bad.
Any thoughts will be appreciated,
If you had ever seen one of these things <distributor> out of the truck,
you'd realize that this is impossible. The portion of the dizzy that mates
with the intake manifold is seperate from the portion under the cap. Look
Shaft seals do go bad, but when they do they leak oil, not air.
Thanks for the response. I have had the dist out. I suspect that the PCV
valve is creating a slight vacuum in the crankcase. There are small holes in
the dist by the camshaft sensor. I was thinking that the pcv valve was
pulling air in the small holes in the dist, down the shaft and into the
crankcase leaving the moister behind in the cap.
I might be reaching? I can not find a reason why dist cap and rotors last
only 2 months. It always acts like moister in the cap.
Try replacing the pickup coil in the distributor:
When the shaft is out, look at the reluctor and see if the metal impregnated
rubber in between the two halves of the reluctor is melted out. Carefully
trim any excess, and put it back together.
I've found that this condition causes ionization, and shortens cap and rotor
life. As well as causes missing under heavy load. Sometimes showing extra
cylynders on a scope.
I fixed em, when the dealers couldn't. That must mean something?
The V-8 HEI Design 3 with the module through the cap does the same thing.
I have replaced the pickup coil in the distributor. When I replace the
distributor cap and rotor it runs good for about 1 month. It might have a
very small miss, but with 150K miles I don't expect it to run perfect. The
old caps have a white ash like build up terminals.
I had the codes pulled at Autozone 3 times. It always comes back random Cyl
When it is very low humidity it runs allot better. When it is humid or
raining the service engine light comes on. At times the light will flash.
Also at high speeds it is much worst (65+ MPH). I can drive it easy and get
by pretty good.
If you think a new distributor would help, I will gladly buy it. I am
grasping at straws and can use any and all help.
Very much appreciated,
Have you tried different brands of caps and rotors?
Matched brands of course?
PS The ash sounds like x, try drilling a 1/4" hole between each pole about
3/4 of the way down the cap, as an experiment. If that stops it, your
problem is ionization, from internal spark.
Like a wide rotor gap.
I have tried caps and rotors from NAPA, AutoZone and Advance auto parts. I
all ways replace both at once. Always matched brands. What is the ionization
from? Is it oil vapor? Very dry days it runs allot better, so I thought it
must be moisture. But I do not know.....
I know that the center of the caps where the rotor touches the cap looks
like it has been hot or shorting though to the #4 cyl. trace in the cap.
There is a path that crankcase air can get to the inside of the
distributor cap - underneath the drive gear, travelling upwards between
the shaft & housing, on up to the cap. There are sleeve bearings to
slow down the process but there are no seals to stop it. This is the
case in my '95 K1500 5.7l which should have the same type distributor.
I replaced the air filter. I don't know if it helped. I have not changed the
cap and rotor since. It is still missing but I don't think it is getting
I hope somebody that has had this problem and fixed it will post.
Thanks for your input. I know a good mechanic with proper tools is worth his
weight in gold. I do not know any good mechanics in my area. Most just want
to replace all the parts that I have replaced twice. My training in
auto-diesel mechanics is from the late 70's. I hate having a problem that I
cannot figure out.
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