97 Vortec 4.3 Dist. shaft seal

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 metal nearby.

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,

Kevin

If you had ever seen one of these things 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 here:

Shaft seals do go bad, but when they do they leak oil, not air.

Doc

Doc,

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.

Thanks again,

Kevin

You're more than reaching dude...............

Doc

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.

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?

Refinish King.

PS 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 misfire

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,

Kevin

truck,

> ULTS&MfrCode=A1C&MfrPartNumber=301639&PartType=218&PTSet=A> >>

Have you tried different brands of caps and rotors?

Matched brands of course?

Refinish King

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.

> > ULTS&MfrCode=A1C&MfrPartNumber=301639&PartType=218&PTSet=A> > >>

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.

Thanks again

Kevin

> > > ULTS&MfrCode=A1C&MfrPartNumber=301639&PartType=218&PTSet=A> > > >>

Thank you for your response. I have done everything I can think of to fix this problem but replace the distributor. Any help is much appreciated.

Kevin

>

Check for high resistance downstream from the dist. The spark will take the easiest path and if you have a bad plug or wire the easiest path may be thru the rotor/cap. H

I have changes the plugs twice. I have changed the wires twice. I made sure the wires are not close to metal. I am out of ideas..

If you have a fix for the problem please post it because I own a 97 gmc pickup with the exact same problem

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 worse???????

If you were to take it to a garage that is good with electronics and has a Tech 2 real-time scanner, they'd be able to find the problem pretty darn quickly. This sounds like something quirky that won't be fixed by guessing, speculating or throwing parts at it. Sometimes there are things the DIY'er can't fix himself as he doesn't have the scan tools to do a proper diagnosis.

Doc

Doc,

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.

You may have a faulty coil. For the cost I have replaced the module and pickup inside the distributor as well.

ULTS&MfrCode=A1C&MfrPartNumber=301639&PartType=218&PTSet=A> >

I have replaced the coil and camshaft module in the dist.

Thanks, Kevin

truck,

> ULTS&MfrCode=A1C&MfrPartNumber=301639&PartType=218&PTSet=A> > >