Help! P0300 Random/Multiple Misfire
 

2002 Blazer LS. 4.3L

Okay so I've had this code for about a year. Random multiple misfire. Sometimes my reader pulls 2 codes. The second being P0300pd? My service engine soon light comes on for a few days and then goes away for a few, then comes back. I changed my spark plugs about 9 months ago to Bosch Platinum. And reset my code. The light stayed off for about 2 weeks but then came back. I put it off for awhile (usually just resetting so I didn't have to look at the code). 2 months ago I swapped the Bosch plugs for some AC Delco (heard Bosch were crap.) AND I also replaced the plug wires. Light went off for about 2 weeks and came back on. I am clueless on what it could be?

I also got a p0141 o2 sensor heater circuit malfunction code 2 months ago. Replaced the sensor when I replaced the plugs. When I pulled the P0300 code 2 months ago, the p0141 code was back. =( Now with a 3rd code. P0141pd.

Any ideas?

Thanks for anyones help in advance

Run a 'search' for both P0300 and P0141 as 'thread titles' and you'll get plenty of info to read. Get back to us with any further questions.

Agreeing with much of the above: you have positive fuel trims which means adding fuel to compensate for a lean condition. That can be many things - fuel delivery pressure, an air leak past the MAF sensor, o2 sensor problems, poor injector spray pattern, various other sensors... you most likely don’t have a vacuum leak because that would get better with more rpm as the percent leak volume goes down but it could be the intake past the MAF. The problem is not even on both banks so it may not be things common to both sides such as fuel pressure/regulator. That said you really should finish the fuel pressure tests as recommended. There are ways to test the spray output of each injector with a pulse box and a fuel gauge. Most here just seem to replace the spider when suspect as applied to doing a balance test first.

Testing the o2 sensors is a little bit of work and they can become sluggish instead of all out failing. If they are suspect a simple thing is to swap sides to see if the problem follows. Mind you that your fuel trims (short term plus long term on a given bank) are not terrible, but marginal. You want the total for a given bank to be under 10. A code doesn’t get set until 25.

George