po300 OBDII code

[gmc]

About 2 months ago my check engine light came on and the vehicle was running real slugglish. It also misfired. I took it to a mechanic, not my normal one, and they told me that I needed new plugs and a new coil pack #5/2. They said the wires were good. Yesterday the light came on again, but went off later in the day and it hasn't come on since. I took it to Autozone to find the code and it read P0300 multiple misfires. What do you think is the problem? It's been running fine so far, but I'm worried that the problem might come back.

The mechanic that did the original repair told me that he warned me that since I wanted AC Delco plats plugs put in the car that it might misfire. He wanted to put in champion plat plugs, but I told him I wanted AC Delcos. I think this is the biggest bull I ever heard! You're telling me that since I went with stock plugs that this is the problem? Think of the millions of GM cars that have AC plugs in them.

1997 boneville

[GMMerlin]

Originally Posted by gmc

About 2 months ago my check engine light came on and the vehicle was running real slugglish. It also misfired. I took it to a mechanic, not my normal one, and they told me that I needed new plugs and a new coil pack #5/2. They said the wires were good. Yesterday the light came on again, but went off later in the day and it hasn't come on since. I took it to Autozone to find the code and it read P0300 multiple misfires. What do you think is the problem? It's been running fine so far, but I'm worried that the problem might come back.

The mechanic that did the original repair told me that he warned me that since I wanted AC Delco plats plugs put in the car that it might misfire. He wanted to put in champion plat plugs, but I told him I wanted AC Delcos. I think this is the biggest bull I ever heard! You're telling me that since I went with stock plugs that this is the problem? Think of the millions of GM cars that have AC plugs in them.

P0300 is a misfire code. Could be 1 cylinder or multible cylinders misfiring.
I would check the plug wires for signs of micro-arcing...this is a blackish powdery substance on the affected plug,wire or coil tower.
if your mechanic replaced the plugs and coil without replacing the affected plug wire than most likely the problem has returned.
Definately some diagnosis needs to be done before anymore parts are replaced.

As far a AC/Delco plugs go...I use nothing else..only the best for my customers

[RABarrett]

Something to bear in mind here is the possibility of a misdiagnosis. GMMerlin is correct here regarding the possilility of defective plug wires. Though I have replaced my share of coils, typically, the plug wires are the culprit. You were correct in insisting on Delco; I typically recommend Rapidfires, not to be confused with Split fires. The Delco Rapidfires were tested by USAC and repeatedly gave better results in tests such as idle stability, off-idle response, etc, over new plugs from any other manufacturer. It has been my experience that , in many cases, Champions of any application add to a problem rather than curing one. I believe, in this case, that the 2/5 plug wire set was the problem, and the replacement plug wires covered it up with their lowered voltage requirement. Even if the code was not cleared with servicing, the ECM will not illuminate a light, setting misfire codes if the problem has been correctly repaired. You might try replacing the plug wire set yourself to save some money in servicing, but I would rather see you pursue this with the individual you PAID to repair the problem. Another lesson; if you find someone you can trust, in any capacity, stay with him. They are difficult to find. 'Nuff said. Ray

[gmc]

Originally Posted by RABarrett

Something to bear in mind here is the possibility of a misdiagnosis. GMMerlin is correct here regarding the possilility of defective plug wires. Though I have replaced my share of coils, typically, the plug wires are the culprit. You were correct in insisting on Delco; I typically recommend Rapidfires, not to be confused with Split fires. The Delco Rapidfires were tested by USAC and repeatedly gave better results in tests such as idle stability, off-idle response, etc, over new plugs from any other manufacturer. It has been my experience that , in many cases, Champions of any application add to a problem rather than curing one. I believe, in this case, that the 2/5 plug wire set was the problem, and the replacement plug wires covered it up with their lowered voltage requirement. Even if the code was not cleared with servicing, the ECM will not illuminate a light, setting misfire codes if the problem has been correctly repaired. You might try replacing the plug wire set yourself to save some money in servicing, but I would rather see you pursue this with the individual you PAID to repair the problem. Another lesson; if you find someone you can trust, in any capacity, stay with him. They are difficult to find. 'Nuff said. Ray

Thanks for your info. The mechanic told me that the wires tested fine. They're still he original wires from 1997. I have 81,000 miles. Like you said though, maybe they weren't correct? Anyhow, the car is still running fine. It never acted up again so far.