97 Buick Skylark 3100 V6 with high idle problem

[donron109]

Hi new to forum, and here's my problem:
Mother-In-Law drives a 1997 Buick Skylark custom with the 3100 V6 with 170k miles. She brings it to me cause it's lurching and she thinks the transmission is failing.
I can tell it's running rough so I take it down and pull the codes and they cascade...
P0300 misfire
P0140 O2 sensor-bank1 sensr2
P0141 O2 sensor-heater circuit bank 1, sensr2
P0121 TPS
P0401 Egr

This car hasn't had a lot of maintenance; MIL puts gas in it.
I'm thinking these problems are all related to a prolonged misfire situation. Start with plugs/wires (the rear plugs look like the originals), I pull the throttle body and EGR, remove a ton of build up and make sure the pintel is free to move in the EGR itself. Replace the TPS. Pulled the IAC and cleaned it.
I put everything back together and see if it runs.
Now the idle is high on start up. Smooth, but fast
Will the O2 sensors settle down with fewer misfires or do I need to replace them? I'm loathe to just throw parts at this car, especially hard to reach parts. Also might be a bit low on coolant.
Am I overlooking any easy fixes?
Thanks for any advice

[pocket-rocket]

The high idle is probably a vacuum leak from pulling the IAC or most likely the EGR. Also make sure the passage from the EGR to the intake is free. I've seen them plugged with a solid mass of carbon before. Took a lot of carb cleaner and a piece of wire to clear it out.

As for the O2 code, since the heater is bad too I would just change it. The sensor as a whole is probably shot. Sensor 2 is the downstream one after the cat so it's easy to get to.

Hope this helps and welcome to the forums

Sent from my HTC One X using Tapatalk 2

[X11_STE]

I agree with pocket rocket. The only other thing I might add is that the TPS must be calibrated to the car and for that you need a scanner (voltage at idle should be 0.5~0.6). That will definately help the high/ rough idle & lurching.
Low coolant will make the car run hot and should be checked along with the oil. Be more proactive on keeping her car maintained and it will last alot longer.

[donron109]

Thanks for the help. Turned out it was the vacuum line running from the PCV to the back. The gasket was under the throttle cable bracket and had cracked thru, allowing free air into the UIM. I went to the auto parts store for a replacement and none were to be had... so I headed to hose leftovers and found a piece of 5/8 radiator hose. This would sit outside of the plastic valve and it was long enough to be held in place by that throttle cable bracket. Started it up and wouldn't you know it the vacuum held. So there it stays.
Changed the oil, checked the lube zerks, put in coolant and gave it a wash.
Then made MIL promise she'd watch the oil/coolant levels when she filled up the gas tank. That'll keep until the next few fill-ups or until there's another problem...
Thanks again.
Ron