Car running rough and my chrome tips are turning black

**initechpeter** · 06-18-2012, 01:59 PM

Yesterday on the way home. My 2002 Trans Am (WS6) started chugging and I lose power. The SES was flashing, but I was able to drive it home.
I put the scanner on and 3 codes came up. P0300 x2 and P0154. I replaced both o2 sensor in front of the cats. P0154 error code gone, but still is showing the
P0300 and the SES light is solid on. After replacing the o2 sensor I noticed my chrome tips covered in black soot. Plugs and wires were changed about 2,000 miles ago.
I also have to mention that I found a crack on my driver side cat between the o2 sensor and the cat. Any ideas?

2002 Pontiac Trans Am WS6
LS1 - auto
159800 miles

**FinZ28** · 06-18-2012, 02:55 PM

How is the car running now? Are you able to clear the code with the scanner? If not, the light will go away after a few drive cycles, unless there is still an issue somewhere. Also, check the spark plug wires and make sure they are properly connected to the coils and plugs. I think it's one click on the plugs, two on the coils.

**initechpeter** · 06-18-2012, 04:12 PM

Checking everything so far. Going to clean the MAF sensor and recheck the plugs, but this puzzling the hell out of me. SES light still appears after resetting it.

**FinZ28** · 06-18-2012, 05:33 PM

Try this (got this idea from pajeff). Wait until it's dark out and open the hood. Start the car and see if you see anything arcing under the hood, especially in the areas where the coils and plug wires are. If you do, you've found your problem.

Cleaning the MAF is a good start, too.

I also read elsewhere that a cracked PCV line caused a similar problem on another LS1 car, so that can be something else to look at. You can take a can of carburetor cleaner and spray it on your vacuum lines. If the car stumbles or stalls, you've located a leak and need to fix it.

**0rion** · 06-18-2012, 06:40 PM

is the crack on the upside of the cat or downside? It could be sucking some air there but that's unlikely the issue. Miles on fuel filter and have you checked fuel pressure at the rail? Do you have access to a scanner to look at fuel trims and what not?

**FinZ28** · 06-18-2012, 07:33 PM

0rion, would a vacuum leak be more likely to cause a lean condition or a rich condition?

**0rion** · 06-18-2012, 10:29 PM

lean.....any unmetered air will do that. Your O2's will then try to compensate for it. There's also a false lean that comes from an exhaust leak pre O2's where the O2's see lean so they dump fuel resulting in rich which is usually where you'll see sooted up tips. Since his crack is on the drivers side though and his code was a passenger side code I doubt that crack is causing a false lean and it would need to be pretty close to that front O2. Right now he's just looking at a random misfire which could soot the tips if it's misfiring enough.

I would start simple by inspecting those wires. Even though they're new that doesn't mean one or more can't be bad or they're not "clicked" into place. I chased a misfire on my truck years ago. First thing I did was replace plugs/wires. Still had it. Replaced the coil, cap/rotor, and eventually the distributor since I'd ruled the plugs/wires out with new ones. Fuel pressure was fine. Pop the hood one night while it was running and saw a tiny arc to the block. One of the brand new wires had a little "hair" sticking out of the boot that was arcing to the block.
I would also look at fuel pressure. Life gets much easier if you can get a scanner to look at live data....it starts to narrow things much quicker. You can look at misfires and see which cylinders are misfiring and fuel trims to narrow it to one side or the other. Just makes trouble shooting these issues much faster and easier.

**initechpeter** · 06-19-2012, 03:49 AM

The crack for the pipe is between the o2 sensor and the cat. I can't see if it goes all the way around, but I can smell exhaust fumes when I have the hood open. I'm thinking this is the cause because the crack is fresh and it was after I had my tranny rebuilt.

**RichWS6** · 06-20-2012, 06:15 AM

I would replace all 4 O2's to be safe, its good to replace them all at the same time, but from the sound of it the Cat is not helping your issue either. I don't think it would hurt to check the plugs and wires as well.

**initechpeter** · 07-03-2012, 05:41 PM

UPDATE - Plugs, wires, coil packs, and MAF sensor replaced. Still getting a P0300 error code. Car still runs rough as hell well below 300-400 rpms now with new parts on. I still haven't had a chance to fix the CAT, but does anyone know if that will affect the car running this rough.

**initechpeter** · 07-03-2012, 05:44 PM

Also replace fuel filter. I don't have access to a scan tool that will give the data. I'm not sure how to check the fuel pressure either.

**FinZ28** · 07-03-2012, 08:56 PM

Originally Posted by initechpeter

Also replace fuel filter. I don't have access to a scan tool that will give the data. I'm not sure how to check the fuel pressure either.

Shrader valve on the fuel line in the engine compartment. You'll need a gauge, which you can buy from any auto parts store. I can't recall the exact numbers you're looking for as far as fuel pressure goes.

**0rion** · 07-03-2012, 11:43 PM

Originally Posted by initechpeter

UPDATE - Plugs, wires, coil packs, and MAF sensor replaced. Still getting a P0300 error code. Car still runs rough as hell well below 300-400 rpms now with new parts on. I still haven't had a chance to fix the CAT, but does anyone know if that will affect the car running this rough.

So the crack is between the front O2 & the cat? If so that could cause your issue. Believe it or not the exhaust will suck fresh air upstream & effect the O2's. I would want to log it though & see what your fuel trims say but the crack could be your issue if it's close enough to the front O2

**BRANDON** · 07-05-2012, 06:19 PM

every case is different but i was having a similar issue a few days ago,on the way home my car started skipping and running rough,long story short,a few days of eliminating possible problems and an o2 sensor,spark plugs,and valve cover gaskets later,found out i had a broken rocker arm,i dont have stock rockers though,i have yella terra roller rockers and they have been known to break,so it may be worth a check...

***SMWS6TA*** · 07-05-2012, 07:53 PM

Originally Posted by FinZ28

0rion, would a vacuum leak be more likely to cause a lean condition or a rich condition?

I'm going of memory here but I believe it causes a rich condition because it adds more air to the system.

**initechpeter** · 07-06-2012, 09:54 PM

Update. I change the spark plugs again and they were black as hell. The plugs only had 2500 miles on them. I put new ones in tonight and everything is working, but I still think my cats are bad since the tips of the plugs were black. So all in all. New o2 sensors (only the ones before the cats), coil packs, MAF sensor, and plugs. The weren't change because I notice everything was working, but I will need to replace my cats. I think they are plugged to the point that they aren't work properly. G*d it feels good to have my baby back and running. I want to thank everyone on this site for the help. Without this I would've been where I'm at right now with this problem. Again Thanks Car Buffs.

**pajeff02** · 07-08-2012, 06:06 PM

The converters themselves have no impact on your spark plug color, however, as noted above the crack could be pulling outside air into the system and resulting in a false lean condition being read by the O2 sender on that side. The black color on the spark plugs is purely from excess fuel. A scanner that will show your fuel trims will tell you if your PCM is adding or subtracting fuel. Once you replace the cat, it will take the car a bit of running to re-adjust unless you manually reset your fuel trims.