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2000 Sierra 4.3L misfires

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2000 Sierra w/ 4.3L engine has had issues with distributor corrosion in the past. First time (2003), dealer replaced cap and rotor and rerouted AC lines. Second time (2005), replaced cap and rotor. Never ran rough or gave any indication before either failure.

After second failure, the engine bucks severely when engine is cold and humidity is high, beginning the morning I picked the truck up at the dealer's shop. Most commonly gives problem when I ease off the accelerator at highway speeds. The dealership said it was plugs and wires. I replaced these and still have the same problem.

Could this be the ignition system again already?

Or could it be related to fuel system (dealer cleaned carbon build-up from throttle body while it was in shop also)?

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You need a new Distributor


Here's the bullitin. Bulliting #03-06-04-041 published on 08/26/2003.



Poor Engine Performance - Misfire, Rough Idle, Service Engine Soon/Check Engine Light Illuminated, DTC P0300 Set (Inspect DIstributor Ignition (DI) System Components and Replace As Necessary) #03-06-04-041 - (08/26/2003)

Poor Engine Performance -- Misfire, Rough Idle, 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, Silverado


2001-2003 GMC Jimmy, Safari, Savana, Sierra, Sonoma


2001 Oldsmobile Bravada


with 4.3L, 5.0L or 5.7L Gas Engine (VINs W, X, M, R -- RPOs L35, LU3, L30, L31)



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.



This condition may be due to high levels of internal corrosion in the distributor, causing spark to go to the wrong cylinder. This corrosion is attributed to a lack of air flow internal to the cap caused by the EIP screens being clogged with debris.



Inspect the internal components of the Distributor Ignition System using the procedure listed below. A new distributor base has been released for service with improved airflow screens.


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.

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.

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.

Inspect the distributor EIP screen. The screens should be free of any debris and the mesh should be visibly porous.

All of these inspection can be done on-vehicle. 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.


In addition, it has been determined on the Sierra and Silverado applications with the 4.3L engine that the A/C accumulator line is routed directly above the distributor area and condensation from that line can aggravate the corrosion condition. For these vehicles, install the foam sleeve, P/N 15190971, to the A/C line. Cut a slit in the sleeve and secure to the line using tie-straps.


Parts Information

Part Number




Cap, Distributor (V6)



Rotor, Distributor (V6 and V8)



Distributor (V6)



Cap, Distributor (V8)



Distributor (V8)



Foam Sleeve

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Within the last month or so, GM has issued a recall which I think covers this engine. At least it did my 2002. It calls for inspection and pulling the screens from the distributor ventilation ports as well as replacing the rotor and cap with upgraded parts. Check it out and I think you will get fixed up. RRW

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