p0300 random misfire code

imamudskipr

p0300 random misfire code

Unread post by imamudskipr » Thu Aug 05, 2010 5:26 pm

What are some good starting points to solve a random misfire code on a 96 bonneville with the 3.3 motor? I have no problem doing the work but would like to avoid just guessing and changing parts at random. I have no diagnostic tools except a cheap scanner i borrowed. code p0300. Thanks for any input.

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butchkaz
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Re: p0300 random misfire code

Unread post by butchkaz » Thu Aug 05, 2010 11:37 pm

A 1996 Pontiac Bonneville would not have a 3.3L, it would be the 3.8L.
Anyway...
A P0300 is misfire, just the older cars do not tell you which cylinder.
Most common on this engine is a bad plug wire. The rear wires are usually the cause, as well as a bad spark plug. Bad spark plug wires also show up when accelerating from a steady speed on the highway. Accelerating causes a heavy electrical load.
Plug wires can be tested by doing a brake-torque and spray the wires with a water spray bottle. The water would cause the bad wire to arch.
Many times the plug wires arch through the boot and into the metal shield around it at the plug. You would hear a snap as it was arching. Also check for corrosion at the wires as it plugs into the ignition coils.
Be Sure To Check The Related Topics below For More Help.

Guest

Re: p0300 random misfire code

Unread post by Guest » Fri Aug 06, 2010 7:24 am

Thanks for the reply. I just did head gaskets on my sisteres caravan, so I have 3.3 stuck in my head. I found out last night the plugs and wires were changed about 2 weeks ago and the plugs may not have gapped. That will be my next check. Thanks again.

Guest

Re: p0300 random misfire code

Unread post by Guest » Mon Aug 09, 2010 9:29 am

Gapped the plugs correctly. Fixed a fuel leak on rear fuel rail. drove for about 30 miles and engine light has not come on but it still shows a random misfire.Chiltons book is useless for injector and coil pack resistance. Any ideas what to try next?

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butchkaz
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Check Engine Light P0300 random misfire code

Unread post by butchkaz » Mon Aug 09, 2010 7:21 pm

Guest wrote:Gapped the plugs correctly. Fixed a fuel leak on rear fuel rail. drove for about 30 miles and engine light has not come on but it still shows a random misfire.Chiltons book is useless for injector and coil pack resistance. Any ideas what to try next?
Assuming none of the plugs is cracked, and the coil towers are not corroded, you may have an injector hanging up, although on this engine, ignition is almost ALWAYS the cause. Especially if the engine is under load. If the misfire shows up at idle, then look for a vacuum leak.
Be Sure To Check The Related Topics below For More Help.

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