Need Help in Diagnosing Rough Running Engine

SuperG · 01-09-2008, 09:31 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, 11:58 PM

Do you have a code reader to see if any DTC's are present?

blk04cobra1 · 01-10-2008, 09:16 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, 09:17 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, 02:38 PM

Typically a bad O2 will trigger a CEL...

SuperG · 01-10-2008, 04:59 PM

Quote:

Originally Posted by blk04cobra1

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, 11:34 PM

Quote:

Originally Posted by SuperG

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, 09:57 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, 03:08 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.

01-09-2008, 09:31 AM	#1
SuperG Registered User Join Date: Nov 2005 Location: Houston, TX Posts: 1,500	Need Help in Diagnosing Rough Running Engine 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! __________________ Gary 1997 with Vortech V-2 SQ-trim 420 Hp/376 Tq at 5psi 2010 Shelby GT500 - Stock http://members.cardomain.com/supergr

01-09-2008, 11:58 PM	#2
Big T Registered User Join Date: Feb 2004 Location: Madisonville, Louisiana Posts: 249	Do you have a code reader to see if any DTC's are present? __________________ 2003 black anniversary edition cobra Current Mods: Polished 2.3L whipple Kenne Bell BAP 60# injectors SCT BA 2600 3.5 whipple pulley with aux idler kit 2# LFP lower pulley dyno tune by L&L Automotive flowmaster american thunder catback bbk x-pipe with high flow cats bbk cai Accufab polished TB polished canton coolant reservoir tank LFP dual pass heat exchanger Polished intercooler reservoir tank upr polished underhood kit with hood prop Autolite racing spark plugs .032 gap hilton boost overlay Mickey Thompson ET Streets 275/40/17 566rwhp 536rwtq on mustang dyno Mods to come soon in order: suspension upgrade 2.75 upper pulley waiting for install

01-10-2008, 09:16 AM	#3
blk04cobra1 Registered User Join Date: Nov 2004 Location: Charlotte, NC Posts: 1,374	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. __________________ 2004 Cobra HP Twin 67's 785rwhp on 9lbs of boost

01-10-2008, 09:17 AM	#4
SuperG Registered User Join Date: Nov 2005 Location: Houston, TX Posts: 1,500	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. __________________ Gary 1997 with Vortech V-2 SQ-trim 420 Hp/376 Tq at 5psi 2010 Shelby GT500 - Stock http://members.cardomain.com/supergr

01-10-2008, 02:38 PM	#5
blk04cobra1 Registered User Join Date: Nov 2004 Location: Charlotte, NC Posts: 1,374	Typically a bad O2 will trigger a CEL... __________________ 2004 Cobra HP Twin 67's 785rwhp on 9lbs of boost

01-11-2008, 09:57 AM	#8
puzzle13 SCMC Member Join Date: Nov 2004 Location: Raleigh, NC Posts: 633	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.

01-12-2008, 03:08 AM	#9
blueblazes Registered User Join Date: Apr 2006 Location: Hickory, NC Posts: 275	did you replace the plugs? I had a rough idle with mine one time and it turned out to be a bad fuel injector.

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