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Check engine light codes problem with my 2002 Pontiac Grand Prix GT.
Engine size = 3.8L non supercharged.
ABS, Track Off and Service engine soon.
GM Computer codes = C0045, C0046, C0245, P0303, P0420, P0172.
Repair work done prior = Reason for code P0420 is because I dont have a catalytic converter.
Work done to repair this problem = Ever since I retreived the code P0303 I have changed all of the spark plugs,fuel pressure regulator, fuel injector for cylinder 3 and switched around coils but still got the code for cylinder 3 misfire.

Question = I only get a misfire when i step on the gas and when i do this my SES starts to flash. OBD code reader reads P0303 cylinder 3 misfire. To correct the problem i have changed out all 6 spark plugs, didnt change the wires because they are working fine. I have switched up the coils to see if it was the problem. So i switched them up and stepped on the gas and again i got a blinking SES light and code reader gave me P0303. I changed the fuel injector for cylinder 3 and still no solution. I also changed the fuel pressure regulator and the oxygen sensor behind the engine on the manifold. I also noticed that after i changed the spark plugs i looked at the one from cylinder 3 and it had little cracks and looked kind of smokey. I changed it and a few days later the same thing happend. As for the ABS and Track Off light on I got the codes C0045, C0046 and C0245. What do these mean? What could the problem be for my misfire?


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Don't be so sure the plug wire on #3 is good.
Several reasons-
A missfire under acceleration (load) is a telltale sign of a spark problem. Hard acceleration puts a heavy load on the ignition system- not so much in the injector.
After changing plugs, that #3 had little cracks ? That means the plug is bad. Small cracks in the white porcelain means it is arcing through, and that is your problem. The plug wire is either scratching the porcelain, or is causing arcing. Replace that wire, and see if the plug is damaged again.
Spark Plug Inspection
ABS code C0045- left rear wheel speed circuit
ABS code C0046- left rear wheel speed circuit
The c0245 is speed sensor frequency problem.
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Okay well i got rid of my abs codes. I checked the sensor and it was not plugged in, so that took care of that. As for my misfire well i changed out the wire and no longer had it misfire when i stepped on it. I couldnt beleive it was just the wire but every now and then when i step on it, it does miss but it does not do it like how it used to. Why is this?


   
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You may have another plug wire that is weak. Not misfiring enough to cause a light or set a code.
Suggest changing all of them.
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2002 Grand Prix GTP Supercharged 3800. Im getting P0172 code (fuel too rich) no black smoke, no soot in the exhaust, and no other codes. Ive changed plugs, wires, 02 sensor just below the manifold, MAF sensor, and IAC.

WHAT DO I DO NEXT??


   
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your code is for bank one running too rich. Did you look at your fuel trims? long term and short term? How far off are they? Running rich means the fuel trims should be negative, taking away fuel. You should look at the bank one sensor one graph and see if it is changing back and forth from below 0.2 to above 0.8 very regularly. Compare bank one to bank two and see how different they are.

I know it's hard to figure out a lot of stuff without a scanner, to see what the engine is looking at, but you might replace a lot of parts before you guess the right one without using a scanner. Even with a scanner many things are hard to figure out now days. Leaky fuel pressure regulator could be allowing fuel into the intake. An Injector that leaks could cause excess fuel to get into the cylinder. Excess fuel could be getting into the oil and being pulled up through the PCV system. A converter getting plugged up can cause the back pressure to affect your MAF of MAP.

Other than getting the code is there any driveability symptoms? Have you looked at the freeze frame to see when the code sets? What the computer saw when the code set. Sets the code at idle or when driving? On decell of acceleration? If it was hot or cold? What bank two was doing when bank one was setting the code.

there's a lot to look at when it's not something really bad. When something is broken, that makes it easier to find but when something isn't really broken but just running outside what the computer is programmed to see, It's sometimes very hard to find. You need all the information you can get to figure out which direction to go. Since all these systems are all inter-related it's hard to pin down the cause without looking at everything that's going when the code sets.


   
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Hey thanks for the insight. I started learning about fuel trims now. However my code reader is just a real basic one that only reads engine codes and i have no idea how to get it into a mode to measure fuel trim. It never came with a manual.

As for performance issues, I haven't really had any. Still have lots of power and no stalling or bogging. a small murmur in the rpm from time to time while idling but nothing erratic or irregular and not very frequent. However if I leave the rich code for too long it will eventually give me a cat below threshold code. i figure cause unburnt fuel is getting into the cat.


   
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Running rich so that the engine computer sets a code may not have any driveability symptoms yet because the computer will compensate for the rich mixture by turning the fuel pulse width down. The problem comes in when the computer is not able to adjust the fuel enough and converter damage happens.

it sounds like your engine is really running rich. You need to find a scanner that will do more. Either find a batter scanner of find someone or a shop that has a better scanner so they can see what your computer is seeing. If the engine runs rich too long and you get a cat efficiency code you are damaging the cat. (if it is not already damaged) You get the cay efficiency code because the rear O2 sensor see the cat not clearing hydrocarbons out of the exhaust. At some point even if you fix the original problem you may still get the efficiency code because the cat can no longer do it's job.

if the tool you have is only a code reader, it will only tell you the stored codes. What you need to find is a scanner. Something that can at least read the data PIDs. Something you can see the O2 sensor reading going up and down. Something that shows you the fuel trim PIDs, so you can see how far off they are from normal. A graphing scanner would be even better because then you can do things to affect the fuel trim and see how the engine reacts to the changes to give you a direction on what to do next.

Without a good scanner you could replace a lot of parts before you guess the right one. Even with a scanner it can be difficult to narrow down what may be the cause of a running rich condition might be, but the scanner with live data streaming will make it much easier to see what's happening.


   
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