Loss of power during acceleration

Ok, Ive got an odd situation. I have an 2002 Impala LS (3.8) with 108k miles, that has what seems to be a loss of power issue.

In the mornings when I go to work, the car drives fine. Its when I either go to lunch, or when I leave work at the end of the day is when it acts up. I can start the car, and when I pull out of the parking lot and accelerate, I feel a sudden loss of power (almost like something is keeping the car from moving). It accelerate, but its real sluggish like I have no power. I then have to let off the accelerator and I can sense the car "chugging" for about 30-45 seconds, and then the power will quickly return in a smooth action and then it will drive just fine.

At times, if I have been driving the car around town alot, or if I have been traveling, it will do the same sudden power loss during acceleration. The difference here is, it doesnt recover that power until I have stopped and turned off the car for 30 mins to an hour.

Every now and then the check engine light will come on during these episodes, but it wont stay on after the car has been off and restarted.

I truly am at a loss, and I am leary of taking it to the shop as I know its going to be a guessing game, and they will want to replace parts until fixed. I dont want to spend a ton of money to replace parts that may not need replacing. I have thought about the Cat going bad as I have read that the 02's had bad Cats, but would it act in this manner? Could it be the tranny?

On a side note, what type of O2 sensors are used on the 02 impala LS. I am looking to buy new ones, but there is a 4 wire and a 2 wire. Short of crawling underneath, do you guys know?

Any thoughts or ideas would be greatly appreciated.

Thanks,

Mike

check your pvc valve and make sure it connected properly and is not sticking it would give cause these kinds of power loss do your rpms drop when you stop maybe and im sure you probaly have but check your air filter also

check your pvc valve and make sure it connected properly and is not sticking it would give cause these kinds of power loss do your rpms drop when you stop maybe and im sure you probaly have but check your air filter also


Air filter is fine. I will check the PVC Valve when I get a chance. I dont notice a drop in RPM's when it happens.

Ok, Ive got an odd situation. I have an 2002 Impala LS (3.8) with 108k miles, that has what seems to be a loss of power issue.

In the mornings when I go to work, the car drives fine. Its when I either go to lunch, or when I leave work at the end of the day is when it acts up. I can start the car, and when I pull out of the parking lot and accelerate, I feel a sudden loss of power (almost like something is keeping the car from moving). It accelerate, but its real sluggish like I have no power. I then have to let off the accelerator and I can sense the car "chugging" for about 30-45 seconds, and then the power will quickly return in a smooth action and then it will drive just fine.

At times, if I have been driving the car around town alot, or if I have been traveling, it will do the same sudden power loss during acceleration. The difference here is, it doesnt recover that power until I have stopped and turned off the car for 30 mins to an hour.

Every now and then the check engine light will come on during these episodes, but it wont stay on after the car has been off and restarted.

I truly am at a loss, and I am leary of taking it to the shop as I know its going to be a guessing game, and they will want to replace parts until fixed. I dont want to spend a ton of money to replace parts that may not need replacing. I have thought about the Cat going bad as I have read that the 02's had bad Cats, but would it act in this manner? Could it be the tranny?

On a side note, what type of O2 sensors are used on the 02 impala LS. I am looking to buy new ones, but there is a 4 wire and a 2 wire. Short of crawling underneath, do you guys know?

Any thoughts or ideas would be greatly appreciated.

Thanks,

Mike
Many things can cause this, erratic fuel pressure, clogged fuel filter, intermittemnt misfire, you should try and get the history codes, and yes this can be failed cat onset symptoms.

I agree with Max that you have the symptoms of a failed converter. GM offers an extended warranty on the converter to 7 years, 120k miles due to a known issue with them on 01-02 W-bodies (this includes your Impala). Check with your dealer, as you could get it fixed for free if the cat is the issue.

On a side note, what type of O2 sensors are used on the 02 impala LS. I am looking to buy new ones, but there is a 4 wire and a 2 wire. Short of crawling underneath, do you guys know?

There are 2 o2's on your car, one pre-converter, (AC-Delco AFS109) and one post converter, (AC-Delco AFS141), and both are 4 wire. There is no 2-wire o2 sensor listed on an 02 impala with the 3.8 (or for the 3.4 for that matter). Tell the "parts monkey" that told you your car could have a 2-wire sensor that he's an idiot.

check your pvc valve and make sure it connected properly and is not sticking it would give cause these kinds of power loss do your rpms drop when you stop maybe and im sure you probaly have but check your air filter also
I agree that pcv or other vacuum line, canister lines ,maf duct loose leaking on intake side, or possible fuel pump going. also check fuel pressure. cat plugged will give constant power loss. bad o2 the check engine light will come on.

I apologize for the delay in replying. Between an ice storm, lost of power, cleanup and business trips, I havnt had time to do much with my car.

The only thing I have done so far is change the air filter (still acting up) and I have ordered new ignition coil packs ( I was planning to do this anyways as they are MSD coil packs).

Thanks for the tips and replies. Once the hectic of Xmas is passed, I will start tracing down the problem with your tips as guidance.


One thing I did forget to mention in my initial post. I have started using premium unleaded, and the power loss is not as severe as it was when using regular unleaded. Im not sure if this is in relation to something, but it might help pinpoint what is going on.

Again, I really appreciate the help and will keep you all up to date with what I find out.


Mike

No connection.

I hope that you all had a great holiday season.

I finally got my issue resolved. I called the local Chevy dealer and spoke with the service dept. I had asked if they knew of the Cat extended warranty. They said they did, so I made an appt and took it in. They called me the next day and said it was the Cat and they replaced it at no charge. They did suggest to have the fuel system cleaned and filter replaced, so I went ahead and paid for that, which was $215. I figured why not, I was getting the cat replaced for free :grinyes:

Wanted to let you all know and thanks for the help and suggestions!

When taking off did your car ever not want to shift durning these times?

Yes, it did have issues with shifting. I seemed like it didnt want to down shift when I did hard acceleration.

I had the same issue with my 03 Impala. Took it to my mechanic who replaced the CAT and found metal shavings in the CAT. He told me about the bulletin for the CAT that chevy had. The bulletin for the CAT did not apply for the 03 even though everything about my 03 was identical to to 02. After much haggling with the GM and being consistent they reimbursed me for my repair...which was a whopping 700 bucks!