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View Full Version : Need Help in Diagnosing Rough Running Engine


SuperG
01-09-2008, 08:31 AM
After running errands, filling up the entire tank on new gas at Conoco, returning home, then starting back up after about an hour, the engine ran horribly, as if it was missing a cylinder or 2.

I pulled the plugs and found all on the passenger side are very black and wet. The driver's side plugs are dry and look like they were firing.

My first step will be putting in new plugs, then I'll switch coils from one side to another to see if any of those are the problem.

Do you think if one or 2 plugs go wacky, that could have a cascade effect on the other 2 on the same side?

Any other suggestions are welcome.

Thanks!

Big T
01-09-2008, 10:58 PM
Do you have a code reader to see if any DTC's are present?

blk04cobra1
01-10-2008, 08:16 AM
Sounds like you could be running a little rich on the passenger side. I would just change out the plugs and watch them a little closer. We typically change plugs at every other oil change (6k miles or so)...they're cheap and it's easy insurance.

SuperG
01-10-2008, 08:17 AM
I do and will use it...for some reason I was under the impression that without a check engine light, there are no codes.

I will also check the O2 sensors...perhaps one is bad sending too much fuel to that bank. I wonder if the O2 sensor is the same as in a SN95? If so, I can simply swap them over and try again. Otherwise, I am not sure how to check an O2 sensor without actually replacing it.

blk04cobra1
01-10-2008, 01:38 PM
Typically a bad O2 will trigger a CEL...

SuperG
01-10-2008, 03:59 PM
Typically a bad O2 will trigger a CEL...
Good point! Well, maybe it's not the O2 sensor afterall...I'll get after it tomorrow and see what I come up with!

Big T
01-10-2008, 10:34 PM
I do and will use it...for some reason I was under the impression that without a check engine light, there are no codes.

I will also check the O2 sensors...perhaps one is bad sending too much fuel to that bank. I wonder if the O2 sensor is the same as in a SN95? If so, I can simply swap them over and try again. Otherwise, I am not sure how to check an O2 sensor without actually replacing it.
I think you can have some codes without the check engine light on but I'm not 100% sure about that.

puzzle13
01-11-2008, 08:57 AM
Some codes have to be thrown 3 times prior to a check engine light. Some codes don't ever cause a check engine light. It all depends upon how serious and what the problem is.

blueblazes
01-12-2008, 02:08 AM
did you replace the plugs?

I had a rough idle with mine one time and it turned out to be a bad fuel injector.