4.3L GMC

I owned a 1995 GMC 4.3L and purchased another new one in 2007. The 07 only has 65k miles on it. 4 times, 2x on the 95 and 2x on the 07, I've had rotor and dist cap problems following warm moist conditions.

Yesterday was about 65 degrees, high humidity, condensation on garage and pole barn floor. Only when humid conditions exist, I may have ingition problems. Last rotor and dist have 20k on them. Took distributor off and discovered rust on the two screws that hold rotor in place. That is a good sign of moisture under the cap. I took a pic of it, will post it later if I can get the new nikon to work. It looks like the spark went throught the rotor to the metal distributor part below.

I kinda wish I had purchased a V8 which has distributor less ignition.

Like I said, this problem has raised it's ugly head 4 times. One time, it left me sitting along the side of the road. That time it had NAPA parts. Really don't think it's part failure as much as it's a GM design problem.

What do you think?

BTW, Bubba found out we are making fun of him. He is very upset with me. I think I'll try to patch things up with a 6 pack.
George

In the early days of HEI, the rotor breakdown was a well known problem, but was soon fixed with a new rotor design & the problem is not often seen anymore. Might want to try genuine GM next time?

May want to check with the dealer to see if there is a service bulletin on that year and model. I think on some years and models there was on that problem.

George,I had the same problem with a 1997 5.7.When you put a new cap and rotor on put light bead of grease around the bottom of the cap that will help it make more of a seal.It cured mine hope that helps.

.
TSB

Jessie,
If I buy into your logic that GM parts are best, then why did the original GM OEM rotor and cap fail with in 45k?

Thanks
George

George Marsh,
I have a 1995 GMC half ton with the 4.3 I now have 193,000. trouble free miles, I haven't had the problems you speak of.
If you are getting moisture in distributor it might not be getting vented properly.

BOB,
My computor can't open TSB. Can you just give me the reader's digest version?
Thanks
George

Copy and paste this.
Might work.
http://www.aatecusa.com/obdIIpro/membersonly/technical-tips/obdii/GM_TSB_03_06_04_041A.pdf

I don't know, George, but you tried NAPA & if GM recognized a problem, then I might expect then to get redesigned parts in the pipe before aftermarket. It appears that this isn't a part problem anyway, but a ventilation problem.
Poor Engine Performance-Misfire, Rough
Idle, Stalls, Engine Cranks but Does Not
Run, SES/Check Engine Light On, DTC
P0300 Set (Inspect Distributor
Ignition(DI) System Components, Replace
as Necessary) #03-06-04-041A - (Jan 28,
2005)
Poor Engine Performance - Misfire, Rough Idle, Stalls, Engine Cranks but Does Not Run,
Service Engine Soon/Check Engine Light Illuminated, DTC P0300 Set (Inspect
Distributor Ignition (DI) System Components and Replace As Necessary)
2001-2003 Chevrolet Astro, Blazer, Express, S-10
2001-2003 GMC Jimmy, Safari, Savana, Sonoma
2001 Oldsmobile Bravada
with 4.3L, 5.0L or 5.7L Gas Engine (VINs W, X, M, R -- RPOs L35, LU3, L30, L31)
This bulletin is being revised to delete a model and add information to subject and
inspection of distributor vent screens. Please discard Corporate Bulletin Number 03-06-
04-041 (Section 06 - Engine/Propulsion System).
Condition
Some customers may comment on poor engine performance and the Service Engine
Soon/Check Engine light being illuminated. Upon investigation, the technician may find
DTC P0300 set.
Cause
This condition may be due to high levels of internal corrosion in the distributor, causing
misfire, rough idle, stall and Engine Cranks But Does Not Run. This corrosion is
attributed to a lack of airflow internal to the cap caused by the vent screens being clogged
with debris.
Correction
Remove the vent screens and inspect the internal components of the Distributor Ignition
System using the procedure listed below. If the distributor base has to be replaced, the
vent screens will also have to be removed on the new distributor. If there is evidence of
this internal corrosion, replace the affected component. Refer to the appropriate
procedure in the Engine Controls sub-section of the applicable Service Manual.
Important: All of these inspections can be done on-vehicle.
1. 1. Inspect the distributor cap. You may notice a white residue on the cap walls.
For higher mileage occurrences, the interior of the cap may have changed to
medium brown in color
2. 2. Inspect the distributor rotor. You may notice the presence of black streaks on
the plastic surface. More typical evidence would be visible green spots on the
copper surface of the rotor segment.
3. 3. Inspect the distributor base. You may notice high levels of surface rust on the
distributor shaft or surface contamination on the sensor hold down screws.
4. 4. Inspect the distributor vent screens (1). If the vent screens are present, remove
them by using a plastic-handled, long blade awl or pick (2). Insert into the airflow
vent screens and pop them out. Refer to the figure for removal procedure. If the
vent screens have been removed from the base of the distributor, then check the
airflow inlets for being clogged with debris.
Parts Information
Part Number Description
10452458 Cap, Distributor (V6)
10452457 Rotor, Distributor (V6 and V8)
93441559 Distributor (V6)
10452459 Cap, Distributor (V8)
93441558 Distributor (V8)
Parts are currently available from GMSPO.
Warranty Information
For vehicles repaired under warranty, use:
Labor
Operation Description Labor Time
J4360 Cap, Distributor - Replace Use published labor operation
time
J4380 Rotor, Distributor - Replace Use published labor operation
time
J4530 Distributor Assembly - Replace Use published labor operation
time
Add To remove Distributor vent
screens 0.1 hr
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They
are written to inform these technicians of conditions that may occur on some vehicles, or to
provide information that could assist in the proper service of a vehicle. Properly trained
technicians have the equipment, tools, safety instructions, and know-how to do a job properly
and safely. If a condition is described, DO NOT assume that the bulletin applies to your
vehicle, or that your vehicle will have that condition. See your GM dealer for information on
whether your vehicle may benefit from the information.
WE SUPPORT
VOLUNTARY
TECHNICIAN
CERTIFICATION
© Copyright General Motors Corporation. All Rights Reserved.

That's been a problem on those, dig out the vent screens in the bottom of the dist. and use GM cap and rotor.

I have an old 2003 Chevy S10 with the 4.3 V6. Bought new. Ignition system has never been touched. Infact, taking it in today for spark plugs 112,700 miles.
Farm truck, stops and starts 20-30 times a day.
Beginning to idle a little rough.

The links Duner and I posted are in .pdf format. You need Adobe Reader to open them.
ADOBE

I drove a '85 ranger that would sweat the distributor real bad . I drove through a moving cold front once and the ignition sweated and almost left me stranded, the next day I bought a cap with a vent on it and never had anymore problems. I don't know if this vented cap was only for a ford 4cyl. or if they made them for other engines.

DELCO cap and rotor ONLY !,,,everything else will fail very quickly , sometimes right out of the box

My 97 Blazer 4.3 has close to 100,000 miles and I don't think the distributor cap has ever been off. Runs fine. What did give me problems a couple of years ago was a poor connection on a piece of wire harness in the steering column. Engine would be hard to start, not idle, stall at stop signs. Replaced that piece of wiring harness in the steering column and it has been good ever since.

Timing chain will stretch and make the distributer lag the crankshaft. The distributer needs an little shaved off it's base and rotated to align the crank Sensor and distributer sensor together again.

Had same problem when I put Autozone brand ignition parts on My 4.3L V-6. Went back to AC/Delco and no problems since. Original lasted 1st 100,000 miles. Replacement lasted less than 5,000. Back to Ac Delco and good as new. Funny thing was went to Chevy dealership and original parts were cheaper than aftermarket!

Scott

Jessie, thanks a lot.

It's weird, they mention removing vent screens and make sure there is ventilation. So if there is ventilation, won't on humid days, moisture get in and cause a problem? Which seems to be what's happening to me.

So, is adding grease to the cap a good or bad idea?

I'm still leaning towards my problem being more of a design issue for Indiana weather, which one day can be winter like, the next day 65, rainy, condensation of garage floor, and I have ingition problems.

Two weeks ago the above conditions happened. Truck wouldn't run worth a darn. I parked it very close to my electric baseboard heater in garage. Opened hood, turned heater on, opened windows just a little to vent moisture out of garage. Next day, problem was gone. This lasted for a few weeks until we had the bad storm yesterday, humid conditions, condensation, truck has same problem again. Almost didn't get it started this morning. Computer code showed it had random missfire. After it ran for about 10 minutes, check engine light went out, problem went away.

I'm 100% convenced my problem is moisture especially with rust on the rotor screws. So how do I vent and at the same time get rid of the moisture? Real catch 22. What makes people think that moisture won't cause the delco to fail? Mine did.
George

I live in a dry climate compared to you & never experience such problems. Not specific to a distributor, but condensation occurs when the temperature on the outside of the window drops below the dewpoint of the air on the inside of the window, so if the window is just leaning up against a post in the yard, it does not exhibit condensation. Therefore, it seems that this is why they want ventilation....same conditions weather wise both inside & outside of distributor. On the other hand, the N-tractors, NAA all use distributor gaskets which seem anti-ventilation????
P.S. some N front mounts did have a vent or two....some didn't. Seen many distributors that for sure had no venting.

I had nothing but ignition problems with my 1997 4.3L.

Dealer replaced cap, rotor, wires, plugs 1 year to the day after purchase. Probably around 12K miles.

Dealer replaced cap, rotor, wires, plugs 2 years to the day after purchase. IIRC around 26K miles.

Dealer found some excuse to NOT replace the cap, rotor, wires plugs, at just shy of 3 years at 35K miles.

I replaced cap, rotor, plugs, wires just about every year after that, for as long as I owned the truck.

Coil blew two separate times, leaving me stranded and paying for a tow.

It NEVER ran right. Always a little buck-buck-buck in the seat of your pants.

CDN,
I think you nailed my problem. Looking closely at things, I discovered not only rust on rotor screws, but under rotor was a white dust. The same dust on the spark plug wires, road dust. Cleaned off dust, put grease on distributor to make a seal, replaced cap and rotor, which Auto Zone replaced for free. Truck runs just fine. I also purchased new wires, however I wanted to know for sure what my problem was so I didn't install them yet.

I even looked at my old delco cap and rotor. They don't look bad. Thinking the cap needs a gasket to keep moisture out. Once again, I'm betting it's a GM design flaw. Post back if problem returns on the next humid day. Hope not.

Thanks to all,
George

Jessie,
Many thanks, Read my last post to CDN. Think I found my problem. I really think the dist screen needs to stay to keep the road dust out.

Thanks again.
George

I've got two 4.3 engines, one in a 95 half ton and one in a 2000 Blazer. I've never had the problems you describe. The 1500 has just over 150,000 and the Blazer has about 190,000. I had really good luck with both with only a failed intake gasket on the 1500. Both were tuned up around 100K with NAPA parts. I'm not a GM guy but these little engines are great for putting around.

If you don't remove the screens, your problems will continue. The vents must be free to flow air. If you look, the bottom of the correct rotor has vanes on the underside to pull air in one side and out the other to expel moisture. You will not have trouble with road dust. Also, make sure the a/c line has insulation on it if it crosses above the cap. Condensation on the hosencan drip off on top of the cap. A bit of dielectric grease on the rotor tip and center is a good idea on those also.

I've got some s-10's with over 220k and several half tons with the 4.3, been pretty darn reliable. Maybe there were some certain years that were worse? I've about turned my head on both s-10's because they're near the end of their life here, but the dang things keep running!

George, thoroughly dry out your distributor & cap, then spray a light coat of WD-40 in them. The "WD" in WD-40 stands for water displacing; also, being an oily substance any condensation wont stick to the metal parts & cause rust or corrosion. Also, don't place the cap on right away after spraying, let the volatiles evaporate first, otherwise you might get a small explosion in the distributor if you crank it over right away. - not good, BTDT. LOL