2003 Grand Am GT seems to hesitate under 3,000 rpm

I have a 2003 Grand AM GT 3.4 with 166,000 miles, its hard to explain but will try. When your first taken off the car seems like its holding back, but then once you hit 3,000 rpm's with the gas pedal still pressed the same amount the car takes right off like it has a power band. Same thing regardless happens all the time under 3,000rpm. Going down the highway at 70 and you start to go up a slight incline, you give it a little gas and you can feel the car having lack of power, then you press a bit more on the gas and it kicks down a gear and goes. Then back in the same situation once back under 3,000 rpm. The car idles normal, check engine light will come on once in a while, but goes back off before i have a chance to see what code it is. I do notice when the check engine light comes on, you can feel the car lack power for just a second. I just replaced the o2 sensor today thinking it was that.

Any help would be great, or if i need to try to explain it a bit more or possibly better i can try.

2 things I discovered, 3 of my plug wires were rusted up internally as were the pins on the coils.(lack of power;misfires) There was a hole in the EGR line(pipe) coming from the exhaust manifold. (Causes similar reaction to a vacuum leak) After cleaning/replacing wires; smearing with dielectric grease and plugging the hole I've had no further issues similar to what you quoted. (I also disconnected the EGR valve permanently)

Hope this helps.

We can't disconnect EGR's in the USA....

If that CE light came on and went off, the code is stored in history....

Correct, here in New York state, if your engine light is on, it will not pass inspection. To check for a code i would have to bring it to the garage on the real computers correct? The hand held ones will not read codes unless the check engine light is on?

ok i ran the codes on it and it came up with P0131 which is the o2 sensor, low voltage bank1 sensor1, i just changed that so maybe that still in there from old sensor. Now the other code i got is P0404 egr , i bet that is causing my issues.

Im gonna pull the egr valve off tomorrow and see if there is carbon build up since gm is known for this

ok bad news, new egr valve in and seems like its doing it worse, could be my imagination. But here is a video. I just changed the o2 sensor and EGR valve, when i ran the code on the car that is what came up with issues. Its hard to here it in the video but the car is holding back, has no power as you can see on how slow the rpms are going up, and it is bucking bad when accelerating slowly.

http://www.youtube.com/watch?v=9zf9sbPLNSg&feature=youtu.be

when i unplug the egr valve, it definitely runs better at lower rpms taking off, but still same results as the video with the rpms not climbing fast, seems like the rpms will not get to 5,000 rpms when holding it to the floor as you can see in the video.

i just removed the upstream o2 sensor and drove it for 10 minutes, hammered on it to see how it ran, it runs normal and rpm's climb right to red line fast. So that tells me one thing, Catalytic Converter is plugged. Im gonna cut the converter off and gutted or just replace it with a test pipe. Where i get my car inspected no worries there.

Well i cut the Cat off today and replaced it with a straight pipe, the power the car has now is unbelievable!! i think the cat been going bad for a while, and just got worse. Cuz i cannot remember the last time my car had this much acceleration! Amazing lol

If left like that, your CE light will come on and P0420 will be set....

If left like that, your CE light will come on and P0420 will be set....

When i removed the converter, i did the spark plug non fouler trick for my o2 sensor also. I drive 65 miles round trip to work and been 4 days so far, all is good. Will keep you posted on if anything changes ;)

i did the spark plug non fouler trick for my o2 sensor also.


Could you explain/describe this?

i bought a package of the Spark Plug Non Fouler PN 42009 at Autozone. I took one of them and drilled the hole out to 1/2 , straight through. Then screwed the o2 sensor into that one, then screwed that non fouler into the other non fouler, and then screwed it into the pipe. The o2 sensor after the converter. (Downstream) the sensor now sits fairly close to the body, but clears it and does not hit the body at all.

CE light still has not come on yet. And i drove it fairly hard on the way home today cuz some little car thought he could keep up lol. Im just amazed how well this car accelerates now. Makes me want to do a few cheap mods to the car now lmao

I have seen a lot of 2003 GM's with bad converters. must of been a bad batch and they never admitted to it. Converter are needed in your state tho, you get pulled over and they see it expect a big fine.

I have seen a lot of 2003 GM's with bad converters. must of been a bad batch and they never admitted to it. Converter are needed in your state tho, you get pulled over and they see it expect a big fine.

I here what you saying, but i have never seen a cop pull somebody over and look under there car. When i had my Talon i ran no converter for 3 years. Been pulled over numerous times for different things :( lol