Help, hesitation or stutter on 2000 Tahoe

I have a 2000 Tahoe with the 5.3L V-8, 351,000 (yes that is correct) miles. Runs great except it has recently developed a stutter, hesitation, skip, I don't really know how to describe it, under acceleration or at steady speed. This is an intermittent problem and it is driving me batty. The only codes are a P0420, maybe after 350k miles it needs replaced? Would that possibly cause this issue, or am I looking at something more sinister?

I think its still got some life left in in. Sounds like either 1) cat is bad 2) oxy sensors are bad 3) other sensors are bad 4) exhaust leak. Yeah I know its vague. Could even be ignition but it would probably throw a misfire code.

Im leaning towards catalatic converter. It could be other things though, do you have any other codes?

Politics on an auto forum?? I thought SleepyHead98 did a great job in his reply, especially the Ign miss, which will cause this P0420 code.

Happy New Year to All

If the engine had miss fires the PCM would throw a p0300 code faster than you know who telling lies.

Like I can solve problems over the internet. The guy just needs to know where to look and I told him.

the forums are to share our own repair experiences to help solve these type issues and save some time/money.

with the question asked I can tell he is experienced in auto repair . also he is a 300,000 mile vehicle owner. that is saying something about his knowledge.

I have a 2000 Tahoe with the 5.3L V-8, 351,000 (yes that is correct) miles. Runs great except it has recently developed a stutter, hesitation, skip, I don't really know how to describe it, under acceleration or at steady speed. This is an intermittent problem and it is driving me batty. The only codes are a P0420, maybe after 350k miles it needs replaced? Would that possibly cause this issue, or am I looking at something more sinister?


my reply to your question got blown away . I stated earlier today to swap the downstream O2 sensors and if you got the p0430 code then the O2 sensor is bad . if the swap results in the same p0420 code then the cat converter is most likely bad. then I would check that the fuel regulator is not damaged with a vac leak .

check fuel pressures so that your sure the injectors and regulator are not leaking down .

Like I stated before, I would suspect cat.

I was vague in what I thought of the other sensors. But as you called out, missfire will flip a CEL faster than anything. and it being the only code that is thrown, its making me think its either the cat or O2 sensor.

If it is some other sensor it would probably throw a code: EGR, MAF etc. Maf would give lean error.

So we arrive back to where we were, its gotta be the sensor or the cat. I thinking cat.

Like I stated before, I would suspect cat.

I was vague in what I thought of the other sensors. But as you called out, missfire will flip a CEL faster than anything. and it being the only code that is thrown, its making me think its either the cat or O2 sensor.

If it is some other sensor it would probably throw a code: EGR, MAF etc. Maf would give lean error.

So we arrive back to where we were, its gotta be the sensor or the cat. I thinking cat.

OK, so I replaced the Cat last night. Runs much better than before, couldn't get it to stumble and had better accelleration. I did notice that in the time it was running while I was putting it on the ramps, only one of the cats got warm. Today it threw the P0420 again, I guess my next step is replacing the O2 sensors at least on the one side?

Im leaning towards catalatic converter.http://www.crazyki.com/20.jpg

Im leaning towards catalatic converter.http://www.crazyki.com/20.jpg

Unfortunately, I replaced the cat last night and it still throws the code. Runs much better, but still got the code today. I'm thinking about replacing the O2 sensors on that side at least.

Unfortunately, I replaced the cat last night and it still throws the code. Runs much better, but still got the code today. I'm thinking about replacing the O2 sensors on that side at least.

so replacing the cat converter and you get the same codes.

I guess your not aware that before replacing these converters you must first make sure you do not have any engine issues that would cause a converter failure/damage.

as you are aware I recommended you swap these O2 sensors reset the dtc and see what codes come on. this is backwards troubleshooting and you may find your new converter will fail soon.

with the engine cold start engine place one hand on each converter they should both heat up at the same rate. using a temp reader see if one is getting too hot . this may mean an engine / fuel failure causing unburned fuel passing to the converter[s]...

OK, so maybe I had a mental lapse after the late night converter install. I must not have cleared the codes afterwards. Cleared them, then after about 300 miles driven, still no codes and it's running great. Before the new converter, the codes would come back every time after the engine reached operating temperature. Thanks for all the help guys.

OK, so maybe I had a mental lapse after the late night converter install. I must not have cleared the codes afterwards. Cleared them, then after about 300 miles driven, still no codes and it's running great. Before the new converter, the codes would come back every time after the engine reached operating temperature. Thanks for all the help guys.

the O2 sensors report the fuel mixture to the PCM if the upstream sensors are not correctly reporting this then the converters will get damaged.

could be with high mileage oil consumption caused the failure.
the O2 sensors should be changed at 140,ooo miles. the upstream O2 is most important. the O2 makers recommend 100,000 miles.

be watchful of the new converter getting too hot. using a temp reader see if they are around the same temp .. good luck