Code P0300


fnawesome
08-05-2010, 03:38 PM
I have a 2000 SLE with a 4.3 and AT and 91000 miles. A few months ago I got a P0300 code when traveling at about 45 mph and accelerating to pass. I got the code scanned at AZ. They suggested a tune-up. Other than the SES light I felt the vehicle was running as normal. Since I had not done any tune ups in the 5 years I've had the vehicle, I replaced cap, rotor, wires and plugs, and cleared the code. I mostly do around town driving at lower speeds. After the tuneup everthing seemed fine. Until a couple weeks ago, I was on the same road accelerating to pass and SES again, P0300 again. I ignored it, because again the car seemed to be running normally. Until this week when I've been doing alot of highway driving, again when driving above 45 mph and accelerating to pass the SES came back on. The SES would blink when I would be accelerating then stay on when speed leveled. Again I wasn't feeling any missing until yesterday on a trip there was alot of hesitating at speed and when sitting at idle it felt like it was going to shut off. I turned car off for about 15 minutes and after restarting it seemed fine again. Any suggestions as to the problem, Please. Thanks

old_master
08-05-2010, 06:01 PM
P0300 is almost always caused by faults in the secondary ignition system, (spark plugs, spark plug wires, distributor cap, rotor, ignition coil). The 4.3 engine is very fussy when it comes to secondary ignition parts. Unfortunately, AZ parts don't have what it takes to keep a 4.3 running well for any length of time. Plugs should be AC Delco 41-993 with a gap of .060". Distributor cap and rotor should be AC Delco with a dab of silicone dielectric grease on each terminal, inside and out, of the cap. Plug wires should be a name brand, AC Delco, Bosch, Autolite, not a "house brand", (Duralast).

Check this thread: http://www.automotiveforums.com/vbulletin/showthread.php?p=6100044#post6100044

fnawesome
08-05-2010, 10:19 PM
P0300 is almost always caused by faults in the secondary ignition system, (spark plugs, spark plug wires, distributor cap, rotor, ignition coil). The 4.3 engine is very fussy when it comes to secondary ignition parts. Unfortunately, AZ parts don't have what it takes to keep a 4.3 running well for any length of time. Plugs should be AC Delco 41-993 with a gap of .060". Distributor cap and rotor should be AC Delco with a dab of silicone dielectric grease on each terminal, inside and out, of the cap. Plug wires should be a name brand, AC Delco, Bosch, Autolite, not a "house brand", (Duralast).

Check this thread: http://www.automotiveforums.com/vbulletin/showthread.php?p=6100044#post6100044

For the tune up I used BWD cap and rotor, ac delco plugs, and autolite wires. I used grease on all the wire connections but not inside the cap. Would it be worth replacing the coil as well.

old_master
08-05-2010, 10:29 PM
The silicone dielectric grease is necessary to help prevent arcing and pitting on the terminals inside the cap. Once pitting has occured, the damage is done. Might be worthwhile installing an AC Delco cap and rotor and use the grease. As far as the coil goes, after dark, open the hood and start the engine, rev it a couple times and watch for arcing around the coil, and wires. Be sure to clear the DTC's after each repair to verify the repair is complete. Check, (and adjust if necessary) camshaft retard. Post your results. ;)

fnawesome
08-08-2010, 10:30 PM
The silicone dielectric grease is necessary to help prevent arcing and pitting on the terminals inside the cap. Once pitting has occured, the damage is done. Might be worthwhile installing an AC Delco cap and rotor and use the grease. As far as the coil goes, after dark, open the hood and start the engine, rev it a couple times and watch for arcing around the coil, and wires. Be sure to clear the DTC's after each repair to verify the repair is complete. Check, (and adjust if necessary) camshaft retard. Post your results. ;)

Thanks for the info. I'm going to try putting the grease on the cap I have. I 'll see how that goes and go from there. Unfortunately I don't have a scanner so I won't be able to check the cam retard. Thanks again.

Nofuze
08-15-2010, 06:49 PM
Just to let you know that I have a 1997 Jimmy and for over 5 years I experienced repetitive P0300 (random misfire) codes. I would go through distributer caps and rotors and within a few months the symptoms would return, especially when highway driving. I finally found a mechanic that knew the answer .... after going through numerous garages. He told me to use ONLY OEM cap and rotor. Do not use an aftermarket product as the quality of the material is not sturdy enough for the Jimmy. He told me that he had several Jimmys and Blazers come in the shop for the exact same problem. I put on the GM cap and rotor and have never again received a code and it's been over a year with alot of highway driving.
Believe me I tried everything else and I was about to pull the distributor shaft to check and clean the filter screen to see if that was causing excessive moisture buildup under the cap. I've never used gease or any other solution and this has worked miracles for me. Almost every garage uses aftermarket parts for tuneups etc. Give it a try ... it's a alot cheaper than other alternatives.
Hope this solves your problem.

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