Mechanics

ENGINE MISFIRE

1996 Oldsmobile Aurora

Engine Performance problem
1996 Oldsmobile Aurora V8 Front Wheel Drive Automatic 159000 miles

I recently had a flashing check engine light and had codes for RANDOM MISFIRE, CYLINDER 5 MISFIRE, AND LOW VOLTAGE O2 SENSOR. I REPLACED THE PLUGS AND WIRES, CLEARED CODES AND THEN JUST HAD A CYLINDER 5 MISFIRE CODE COME BACK. I replaced the coil pack and now the same CYLINDER 5 MISFIRE code is back and now flashing just occasionally. I can feel the misfire more at idle and when engine is cold, but smooths out when warm and at highway speeds. I am lost. Please help! (4.0L V8 baby northstar, as you already know) Thanks.
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Jclemens
January 14, 2010.



When was the last tune up? Did you replace the spark plug? If everything is recient, make sure the plug wires are good and then we need to check the temp sensor. It could be causing the engine to run too rich and foul out that cylender if the plug is weak. Also, check the crank sensor to make sure it is clean and doesn't have oil or grease on it.

Let me know what you find.

Joe

This sound more like a lean misfire. Check the injector for that cylinder. Also you could have oil fouling that plug. Though I doubt it, since you definitely see black smoke coming out of the tail pipe.

Don't bother with fuel/injector cleaner. That stuff is snake oil in a bottle. The only " Injector cleaner" that works is the industrial strength cleaners that takes a mechanic and specialized equipment to install. (You cant' buy this stuff over the counter)

If you are so mechanically inclined, you could allow your engine to run while misfiring for 10-15 minutes or so. Then shut her off and pull each plug one at a time. This will allow you to see which cylinder was misfiring by the color, wetness, smell of each plug.

Finally, it's NEVER a good idea to hunt for a problem by removing/replacing parts. This NEVER works and only costs you a ton of money you could've spent on a technician to do it right the first time.

If I've helped you, please vote for me, as I depend on this to pay my bills. Thanx, Ernest.

Ernest Clark
Jan 24, 2010.
Yes I had a tune up new spark plugs, new wires oil change, fuel filter, new coil pack and fuel injector but im gonna check the crank sensor and get back to you

Tiny
Danm24
Feb 24, 2010.