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OK in the last couple of months I've noticed that my engine is running rough (2002 Suburban 5.3L Vortec 5300 L59 w/95,000mi). It seems to be worse on very cold days to the point that it makes me think that the engine is going to die but it just keeps chugging along. On warm days you don't even notice it. When this started my "Service Engine Soon" light kicked on (not flashing....just came on). The light will sparatically go off for a few days and then come back on. When the weather is consistently warmer the light will go off and when it's cold for days it goes off.
I keep the maintenance up. I'm coming up on a scheduled tranny service. Obviously I'm reaching the end of the projected window for the life of the spark plugs. So regardless of what the problem is I'm going to change them as well as the plug wires.
My question: Does the on-board computer detect misfires?
If so I'm assuming that this is why the light kicked on.
If not then what else could trigger the error that could be related to the symptoms above?
I've considered that because I may have a plug or more misfiring that I could be bugging up my O2 sensors....which would also throw an error.
FYI-I plan to take this to a shop but atm I'm sitting at work typing on this message board looking for input. So spare me the lecture about how I shouldn't trust the opinion of those on a message board. Also I know that there are a few mechanics that frequent this board. I'm asking for input from the pros and others who may have had similar problems before...not asking for input from amatures or those who know nothing about this issue. Thanks.
If you have 95K on the original plugs, notwithstanding GM's claim that they are good for 100K, they are probably pretty worn and probably replacing them would improve things.
Any decent shop can read the code that's been stored. I am not certain that this particular vehicle detects misfires, but I do know that some BMW cars do.
Most chain auto parts stores will read the code for free, if you just want to know what code has been set.
If your O2 sensor(s) is original, it's about due too.
If it was me, I'd test the spark plug wires, if they are OK no need to change them, or have the shop test them, unless they know that the factory wires are "only" good for about 100K
Run the truck at night in complete darkness. Lift the hood and look closely at the spark plug wires and connections as well as near the distributor cap and coil. Often you can see blue sparks arching to ground....indicates breakdown of wires or seals.....replace the wires, plugs, cap and rotor. On chevy trucks one of the most common problems is a deteriorating rotor/ distributor cap. Coils tend to die about this age as well.
Kracer,
No distributor on this motor. It's got a CPP (Coil Per Plug) set up. That may not negate your theory. For grins I'll try it to see what happens.
Anybody care to shed some light on what the problem(s) may be?
P0300 seems to indicate a problem with the plugs.
PO300 Random cylinder misfire. Could be the plugs, or a host of other things. Seriously doubt the plugs, but not impossible. The other codes are there because of the misfire.
GM does have misfire data on a good scanner, which any decent shop will have. Most likely, your vehicle will never get fixed without it, unless you just go replacing just about everything on the engine.
Changing the plugs if they've never been changed can't hurt, but I wouldn't promise that would solve any problems.
Someone mentioned cap and rotor, but your 2002 doesn't have those. It has a distributorless ignition, and I think there's a coil for each cylinder on that one.
Anybody care to shed some light on what the problem(s) may be?
P0300 seems to indicate a problem with the plugs.
DTC P0171 or P0174
The powertrain control module (PCM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. Fuel delivery is controlled differently during Open and Closed Loop. During Open Loop, the PCM determines fuel delivery based on sensor signals without oxygen sensor (O2S) input. During Closed Loop, the O2S inputs are added and used by the PCM to calculate short and long term fuel trim fuel delivery adjustments. If the O2S indicate a lean condition, fuel trim values will be above 0 percent. If the O2S indicate a rich condition, fuel trim values will be below 0 percent. Short term fuel trim values change rapidly in response to the heated oxygen sensor (HO2S) voltage signals. Long term fuel trim makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1. If the PCM detects an excessively lean condition, DTC P0171 or P0174 sets.
DTC P0300
The powertrain control module (PCM) uses information from the crankshaft position (CKP) sensors and from the camshaft position (CMP) sensor in order to determine if engine misfire is occurring. By monitoring the variations in the crankshaft rotational speed for each cylinder, the PCM is able to detect individual cylinder misfire events. A misfire rate that is high enough can cause damage to the 3-way catalytic converter (TWC). The malfunction indicator lamp (MIL) will flash if TWC damaging conditions are present.
The conditions for running these DTCs vary, but I can post more once the code has been established.
P0171: (P0174 is the same as P0171 except it's on Bank Two) Definition
Fuel trim bank one condition
Explanation
The powertrain control module uses the oxygen sensor to calculate the air/fuel ratio of the engine. The computer has recognized a rich or lean condition on one engine bank only.
Probable Causes
1. -If bank one and two codes set together suspect fuel pressure or MAF (Mass Air Flow) Sensor
2. -Oxygen sensor defective
3. -Ignition misfire-repair
4. -Fuel injector problem
P0300: Definition
Cylinder misfire detected - Random cylinders
Explanation
The powertrain control module monitors the crankshaft speed and has detected a misfire condition
Probable Causes
1. -Ignition system fault -spark plugs(s), ignition wires, coil(s)
2. -Vacuum leak
3. -Injector fault
4. -High or low fuel pressure
There are common threads between the two separate faults.
1. Fuel Pressure (Fuel Pump problem or possibly Fuel Filter needs replaced?)
2. Fuel Injection Issue (Because it's on Bank 1 and Bank 2 that would indicate that more than one fuel injector needs to be replaced. If I understand correctly fuel injectors don't fail that often and the odds that more than one has failed....on two separate sides of my engine?)
3. Ignition (Spark Plugs, Plug wires, Coil, Coil leads,etc)
My instincts tell me that it's the plugs. They're old and should be replaced (regardless of what the issue is). If the plugs weren't firing that would lead to excessive oxygen in the exhaust which would cause faults P0171 & P0174.
Fuel + Air => Hydrocarbons + Nitrogen Oxides + Carbon Dioxide + Carbon Monoxide + water
....assuming the combustion is perfect
And because we are getting the misfire code P0300 that seems to supports the case.
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quick and dirty
