Chevy Astro and GMC Safari Forum banner

Code 300: Random misfire

12K views 27 replies 8 participants last post by  twelvestring 
#1 ·
Anyone know the most likely cause for this issue? Just showed up today.
 
#2 ·
Distributor cap is what I hear that is most common , the short design limits ventilation , make sure you get a high quality cap and rotor preferably with brass terminals and there are vents in the distributor housing that have screens that get plugged up and need to be removed but there are other causes as well
 
#5 ·
longyard said:
NY Safari TONKA said:
What was the last things done to the van?... :shrug:
Just completed:
1. power steering pump
2. Water pump
3. Fuel pump
4. All new fuel lines
5. New harmonic balancer
6. New radiator
7. Upgraded alternator to 200amp
8. New idler and tensioner pulleys
Oh... and I upgraded the sparkplugs to NGK irridiums. I've driven the van very little, and so am not very familiar with it. Really today is the first drive I've taken in it since I drove it home two months ago (100 mile trip, no issues.) I should note that it was very humid, and sometimes rainy, today, which lends credence to the distributor cap theory.
 
#6 ·
I had the same problem whenever it rained. Changed the cap and rotor but it still kept refusing to start in wet conditions. One day when it wouldn't start I pulled the dog house and cranked it. I heard an electrical clicking. When I looked at the engine while cranking it I could see a little lightning bolt shooting across the top of the coil. I replaced that and was good to go. I'm not saying you need a new coil, but I think it would be worth it to pull the cover and crank it on a day when it won't start.
 
#7 ·
gillbates said:
I had the same problem whenever it rained. Changed the cap and rotor but it still kept refusing to start in wet conditions. One day when it wouldn't start I pulled the dog house and cranked it. I heard an electrical clicking. When I looked at the engine while cranking it I could see a little lightning bolt shooting across the top of the coil. I replaced that and was good to go. I'm not saying you need a new coil, but I think it would be worth it to pull the cover and crank it on a day when it won't start.
Thanks Gill. I'm going to get a new coil to add to the new distributor cap I bought. Is it hard to change the coil? Thanks. Bill
 
#10 ·
Ok look here make sure your timing its god chk complete w/Tach....if problem still CHECK YOUR CRANK SENSOR :wave: ...Let us know how it goes....You can chk the voltage on the sensor (at connector Pink or Lt Green wire) w/key ON car off should have about 11.5 Vlt...if any chk blown fuse + wires...
 
#11 ·
NY Safari TONKA said:
Ok look here make sure your timing its god chk complete w/Tach....if problem still CHECK YOUR CRANK SENSOR :wave: ...Let us know how it goes....You can chk the voltage on the sensor (at connector Pink or Lt Green wire) w/key ON car off should have about 11.5 Vlt...if any chk blown fuse + wires...
Okay. Can you tell me if timing the beast is as simple as lining up the marks on the timing cover and the crank balancer? Those are the only marks I see.
 
#12 ·
I don't think there's much you can do with the timing on an 01 as the distributer only goes in one way. It's not like the good old days when you could loosen it and move it back and forth. Damn computers.

If you do change the coil, and you still have the original, you have to drill out the rivets that connect it to the brace. The new one will come with bolts and nuts. But like I said before, while that was my issue it might not be yours. But pulling the cover and cranking it while it's in non-start mode may (or may not) help you find out.
 
#14 ·
NY Safari TONKA said:
Can you put up a pic (distributor area) to see for sure what systm you have if EDI (no timing)...if HEI (timing)...I blv after 1995 was the EDI...the misfire it signal by the Hall Effect
I've got a 2001 and the distributor doesn't look like any HEI I've dealt with before. I don't mind replacing parts on a vehicle that's got all it's original stuff after 130K and long exposure to salt on the roads from upstate NY. (I'm down here in NC.)
 
#15 ·
The timing is non-adjustable. One other area to look at is the distributor gear itself, these motors are notorious for eating up distributor gears.( I have 3 of these vans, and I've had to replace the gear on 2 so far). If you see ANY groove worn in it, replace it.
 
#16 ·
Ok Im looking back at what you have change vs old school mech.... :doh: ...when you get a code P030x its at one of the cyldrs...but a P0300 its on ALL... :?: ...What moves in all cyldrs?...SO THATS THE ANSWER FOR YOUR PROBLEM ... :screaming: ....ANYONE!!! for a VICTORY BANANA DANCE :banana:
 
#18 ·
...........There are numerous causes of a P0300. It's more than likely ignition related. :2:
 
#19 ·
Would you say, when it is ignition related its P0300x (x=cylndr #) ... :confused: ...But when its P0300 (code comes by itself not with other P0300x) ITS A RANDOM MISFIRE....Bcs its MISFIRE thats where people say it ignition related :think:

All IN A CAR THAT WONT START ITS IGNITION RELATED :rofl: =NO IGNITION NO BOOM! :eek:
 
#20 ·
It can be fuel related, but more often than not, it's ignition related. Go buy yourself a factory service manual. If the engine runs and the fuel pump is not up to correct pressure, one symptom people usually mis-diagnose is that they have a transmission problem. This ISN'T your dads Oldsmobile.
 
#21 ·
Hey JUST TRAYING TO HELP THE GUY...Maybe sice you went there YOUR DAD.. :naughty: .. DIDN'T SHOW YOU SOME RESPECT when he was working in that OLDSMOBILE + TOLD YOU READ BEF :blah: ....

Re: Code 300: Random misfire
by NY Safari TONKA » May 21st 2011, 10:50am

:banghead: ...DON'T...Parts to chk for this problem = Vac Leak...Your Fuel Pump or Your EGR..IF After AFTER MAKING A 100% SURE ALL ARE WORKING if problem still let us know ....

:think: ...What DO YOU NEED TO HAVE IGNITION... :cheers:

:think: ...GOOD MECHANICS DONT NEED YOUR BOOKS... :wave:

NOW MAYBE YOU CAN PUT ALL THAT... :blah: ...a side and let the por guy chk his car!!!... :banana:
 
#22 ·
P0300 random misfire can be several things that can cause a cylinder not to fire , with the astro it was very often ignition , the distributor vent screens being plugged up or the dist cap because of the short cap and not enough ventilation , this was the case so often that GM issued a Technical Service Bulletin for this

I have uploaded it many times in the past , but the site still has problems uploading now so here is the text of the TSB without the pic :

GM_TSB_03_06_04_041A.pdf

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.

nformation

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

Use published labor operation
J4360 Cap, Distributor - Replace
time

Use published labor operation
J4380 Rotor, Distributor - Replace
time

Use published labor operation
J4530 Distributor Assembly - Replace
time

To remove Distributor vent
Add 0.1 hr
screens

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 WE SUPPORT
provide information that could assist in the proper service of a vehicle. Properly trained VOLUNTARY
technicians have the equipment, tools, safety instructions, and know-how to do a job properly
TECHNICIAN
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 CERTIFICATION
whether your vehicle may benefit from the information.

© Copyright General Motors Corporation. All Rights Reserved.

Here are a couple links that address this matter as well

http://www.obd-codes.com/p0300

http://www.random-misfire.com
 
#23 ·
Phantom said:
P0300 random misfire can be several things that can cause a cylinder not to fire , with the astro it was very often ignition , the distributor vent screens being plugged up or the dist cap because of the short cap and not enough ventilation , this was the case so often that GM issued a Technical Service Bulletin for this

I have uploaded it many times in the past , but the site still has problems uploading now so here is the text of the TSB without the pic :

Phantom,
THANKS SO MUCH!!! for posting the bulletin. This weekend I changed the distributor cap, scrapped clean the rotor tip clean, and changed the coil. I could not find the vent screens. Where are they?

Thanks so much,
Bill
 
#24 ·
longyard said:
Phantom,
THANKS SO MUCH!!! for posting the bulletin. This weekend I changed the distributor cap, scrapped clean the rotor tip clean, and changed the coil. I could not find the vent screens. Where are they?

Thanks so much,
Bill
You are welcome,

They are in the base of the distributor , there are 2 of them and as I recall when facing the dist from inside the the van one hole on the left and one hole on the right , using a long tool like an awl you push the screens out the bottom. Cap and rotor needs to be removed for access , you may need a flashlight to see them
You should check for how much movement of the dist shaft has , it should barely turn by hand , if it moves a lot the gear on the bottom of shaft may have excessive wear and that can cause
"spark scatter" and cause a random misfire .
 
#25 ·
NY Safari TONKA, I'm not gonna get in a pissing match on this thread, I do, however have 3 of these vans, ranging from 1995 to 2001, and without a factory service manual, you're at the mercy of others, and the mechanic Gods to figure out problems with them. They are NOT the same as working on an old HEI carbureted Chevy ( or Ford or Dodge) for that matter. That being said, I've worked for GM dealers, and though I wasn't a master tech, we had plenty of ASE certified (and GM trained) mechanics that relied on service manuals, and Tech II's to diagnose issues on the vehicles. A modern day "real" mechanic, needs information on how the computerized systems operate.
That being said, :goodpost: Phantom!
 
#26 ·
All - there is another possible problem causing a P0300, or even P0301 - 0302 - 0303 & 0304 codes. The EFI system is notorious for clogging, especially with the newer gas that has 10% or more Ethenol. How many miles on van and are they more city or highway? If the miles are 90k or greater it is likely that the EFI system is clogged. To clean this the best you need to use either GM Top Engine Cleaner (TEC) or Seafoam. Instructions on how to use Seafoam are located at www.seafoam.com.

Below are instructions from GM for the 4.3L Vortec used in a bunch of models:

The following is straight from a service manual, in regards to the TSB issued for a "cold knock" on the northstar, caused by excessive carbon.

Before considering major engine repairs, the technician should perform the following procedure to clean carbon from the engine combustion chambers.
Note: This procedure must be strictly followed. Hydrostatic lock may result causing severe engine damage if this procedure is not strictly adhered to. (that's important.)
1) Obtain one can of GM TOP engine cleaner (TEC) P/N 1052626.
2) Start the engine and bring the engine coolant temp to 200 degrees on the instrument panel gauge. (220F on a scan tool)
IMPORTANT: Do not raise the engine speed above idle
3) with the engine idling, disconnect the PCV hose from the PCV valve and slowly spray the TEC into the end of the hose.
4) Raise the engine speed to approximately 2000 rpm until you see a cloud of white smoke coming out of the exhaust pipe, then shut off the engine.
5) Let the vehicle sit for at least 20 minutes, preferably overnight. This allows time for the TEC to act on the carbon deposits.
6) Once the soak period has been completed, start the engine and proceed to remove the remainder of the TEC from the engine by increasing the engine speed to 2000rpm until the white smoke has diminished.
For engine-diy-novices, I recommend you follow that advice, and make SURE you get the aerosol can of TEC. It's much less likely to hydrolock the engine, and you can't pour it in too fast like you can with the bottle. After you finish the above, take it on a highway on-ramp, and with the shifter in 2nd, floor it. You can further exercise the rings by letting the car speed drop to 30mph, and flooring it back up to 60....

I have had great success with Seafoam and a new product that is a spray. It includes an extra long spray hose to get past the MAF and deep into the EFI. The big hint is to get the engine reving at 1200-1500 rpms while srpaying into EFI. Let the van sit for at least 20 min, but I let it sit over night. What a difference in power and MPGs just by getting the carbon crap out. If the exhaust spits out a lot of dirt, then it is best to do an oil change. I also used an oil flush with this first oil change. I have been doing this now for a year on my 1999 Astro with 170K miles.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top