PontiacBonnevilleClub.com

Hi all. I'm back with my non-modded 2000 Pontiac Bonneville SLE. Car has around 165,000 KM’s (102,000 miles)

The last few months, it has had a weird stumbling when starting it cold. It will fire right up on the first attempt, but will chug for around 10-15 seconds before smoothing out, and then running great. If I rev it for a second, it evens out, and runs great. I cleaned the MAF about a week ago, and though it performs better, this problem is still there. Also, today, the service engine soon light came on. According to my scanner, it is a P0420. I have checked the Live Data, and it says my 02SB1 S2 bounces around from .600 to .800 .

From what I can find, this could mean a bad cat, or a bad 02 sensor. I found a website with trouble shooting, which said to monitor the live data of the rear 02 sensor, while slightly unplugging a large vacuum hose, and look for a change. When I do this, the sensor level drops dramatically, to around .100 or so. According to the website, this tells me the rear 02 sensor is working correctly. Would you agree?

Also, when I am in a alleyway, I do hear a rattle, sounding like a bad catalytic converter. And, when I go over a speed bump, something on the bottom of the car scrapes it. I have been meaning to get this looked at, but have been too busy, so I just avoid speed bumps

Should I replace the 02 sensors, or the catalytic converter, or do more diagnostics? Any help is greatly appreciated.

On another note, the engine has what I describe as a 'tick'. I have uploaded a video to Youtube. If anyone out there has good ears, and a minute to take a listen, it would also be greatly appreciated.

http://www.youtube.com/watch?v=qT83v-vgTZI
http://www.youtube.com/watch?v=ESRVAwtPFHg

Thanks again everyone, and have a great weekend.

Can you tell where the tick is coming from? Lifters or radiator fan are my two guesses.

Your first video is locked as private.

Get a hammer and tap on the cat converter to see if it makes any noise. From what you have done and described it sounds like the cat is bad. I would get the car up on ramps or a lift and inspect the exhaust as some of the supports might be broken or have issues. It should not be rubbing on anything.

vogie01 wrote:Can you tell where the tick is coming from? Lifters or radiator fan are my two guesses.

Your first video is locked as private.

Get a hammer and tap on the cat converter to see if it makes any noise. From what you have done and described it sounds like the cat is bad. I would get the car up on ramps or a lift and inspect the exhaust as some of the supports might be broken or have issues. It should not be rubbing on anything.

Thanks for the reply. It definitely sounds to me like it's coming from under the rocker covers(?). Sorry, my mechanical lingo isn't all that great these days. Do you have any recommendations on fixing this? Is this just a common sound on these engines, or should something be repaired/replaced?

I have changed the settings on the video. Sorry about that!
I will get the car up, and inspect. Thank you so much again!