2002 Impala LS dies at idle when warm

Hey all, first time poster here. I have a 2002 Impala LS 3.8L with 103k miles and it was running fine. I decided to get the 100k maintenance done and changed the plugs & wires. The plugs I used are AC Delco 41-101s (.060 gap i checked) which are the direct replacement for the stock plugs. I used Duralast plug wires from Autozone.

I installed the front 3 plugs (1, 3, 5) & wires first because that's all I had time for and the vehicle ran normal for 2 days. Then I installed the rear plugs (2, 4, 6) & wires and it seemed normal at first. I went to run an errand and once the vehicle was at operating temperature it would stall at lights and stop signs when idling (800~ rpm). It starts back up with a little coughing. I'm able to keep it from stalling with a little gas at 1000rpm. The RPMs do NOT flutter when I give it gas and hold it, only when idling under it's own control. When the motor is stone cold it will idle fine until it hits operating temperature then sputter and die (did this in my garage). If I revved the engine while in park it sounds normal up until 4000~ rpms then starts to sputter. I put all the old plugs and wires back in and it still stalls. There are no check engine codes and I triple checked everything to make sure of a tight fit. The plug wires are on the correct plugs.

I'm at a loss here! Car has ran great in the 45k miles and 3 years that I've owned it. I would think if it was an O2 sensor or idle air control sensor it would throw a code?? Any input is appreciated.

Stupid question.....I just correspond the numbers on the coil packs to the cylinder numbers right? The firing order is 1-6-5-4-3-2. I don't have to route from coil #2 to cylinder/plug #6 do I?

Drove it to work this morning. Took the freeway and set cruise control at 60mph which puts the rpms around 1800~. RPMs stayed constant, no surging. I'm getting a faint exhaust smell in the cabin though. Would an exhaust leak or bad catalytic converter cause the symptoms above without a code?

Drove it to work this morning. Took the freeway and set cruise control at 60mph which puts the rpms around 1800~. RPMs stayed constant, no surging. I'm getting a faint exhaust smell in the cabin though. Would an exhaust leak or bad catalytic converter cause the symptoms above without a code?

you may have disturbed a vacuum line or electrical wires/connectors...check .....I do like you style as you reinstalled the old parts..... most would have thrown out...... but it is possible this is a fuel problem.....

you may have disturbed a vacuum line or electrical wires/connectors...check .....I do like you style as you reinstalled the old parts..... most would have thrown out...... but it is possible this is a fuel problem.....

Yeah, I spent 3 hours going over the motor trying to find a disconnected wire or vacuum line. I kept thinking I MUST have knocked something loose but I just couldn't find anything. I never manually disconnected anything except the plug wires and the O2 sensor wire which I plugged back in. I did find one loose connector near the alternator on the harness near the top passenger side of the engine, but it was dirty and looked unused. The connector had a short wire and I could not find any female plugs within range.

Believe me I didn't want to reinstall the old parts because my knuckles were getting trashed on the rear plugs, but I'm pretty thorough and knew I had to at least try. I'm actually going to try the old rear plugs again tonight to make sure I'm not crazy, if it's still pooched I will have to take it into a shop tomorrow morning and pay the $120+ for a diagnostic. :runaround:

Could be a fuel problem too...would be a huge coincedence that it happened while I was changing the plugs though because it ran fine before. I hate engines sometimes.

(Also figured out when I spoke with a mechanic that the sputtering at 4k~ RPMs while in Park is in fact a rev limiter. I didn't know the revs were restricted lower in Park. So basically I just have the idle issue and what seems like less power.)

After having a shop run diagnostics on it they told me it was a bad O2 sensor. Unfortunately I thought a bad O2 would throw a code but I guess it doesn't depending on how far gone it is. And having it go bad at the exact same time I changed my plugs was a horrible coincidence that made me think it was something I did. The only bright side to this debacle is I got so good at installing and removing my plugs I can do the whole job in 25~ minutes.

...... The only bright side to this debacle is I got so good at installing and removing my plugs I can do the whole job in 25~ minutes.

Want to come over to my place and do my plugs and wires?!?!... Good job but a strange coincidence... To my knowledge a bad O2 sensor should throw a code...

Want to come over to my place and do my plugs and wires?!?!... Good job but a strange coincidence... To my knowledge a bad O2 sensor should throw a code...

I agree that if the O2 was bad enough to cause drivability issues it should throw codes.....since your getting good at this that 120.oo could have gone toward a scanner.......

Want to come over to my place and do my plugs and wires?!?!... Good job but a strange coincidence... To my knowledge a bad O2 sensor should throw a code...

For good beer and a decent steak I'd consider it. :naughty:

Did replacing the O2 sensor fix your problem? I am having the exact same problem. The O2 sensor did actually give me a code. So I did replace it, but this did not fix my problem. I am afraid it might be the fuel pump. But if you have any other suggestions, it would be greatly appreciated. I have replaced the fuel filter, spark plugs, and wires.

Did replacing the O2 sensor fix your problem? I am having the exact same problem. The O2 sensor did actually give me a code. So I did replace it, but this did not fix my problem. I am afraid it might be the fuel pump. But if you have any other suggestions, it would be greatly appreciated. I have replaced the fuel filter, spark plugs, and wires.


you should start a new posting with your issues...try to give a good description of what you found and symptoms...

Did replacing the O2 sensor fix your problem? I am having the exact same problem. The O2 sensor did actually give me a code. So I did replace it, but this did not fix my problem. I am afraid it might be the fuel pump. But if you have any other suggestions, it would be greatly appreciated. I have replaced the fuel filter, spark plugs, and wires.


Yes, replacing the O2 sensor did fix my problem. You did replace the upstream sensor, correct?