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rough run open to closed loop
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dogman Offline
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Post: #1
Exclamation rough run open to closed loop
I am having an issue with my car running rough (temporarily) when it switches from open to closed loop after startup. I recently had the pre-cat O2 sensor replaced. It started that same day. Talking to my mechanic today, he thinks the post-cat O2 may be reacting to the new pre-cat O2. I have been watching the O2 readings on my scangauge. The pre-cat is showing normal fluctuating values. The post-cat is showing slow changing values between 45 and 65 at 65 mph on the highway. My mechanic said it should fluctuate more than that. I originally thought it may have been the EFIE causing the problem. I disconnected the EFIE and ran everything stock and the problem still existed. Does anyone have any thoughts?

Doug
2003 Buick Lesabre Limited
3.8L V6
Minot, ND
12-15-2008 07:24 PM
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colchiro Offline
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Post: #2
RE: rough run open to closed loop
Hi Doug.

Did you try clearing the ecu (disconnecting the battery)?

Rick

Links: Documents / Tuning for Mileage | Toyota Sensors | Autoshop Sensor Tutorials
12-15-2008 08:11 PM
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dogman Offline
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Post: #3
RE: rough run open to closed loop
No, I have not. How long should I leave disconnected? I actually drained my battery this morning trying to start it.

Doug
2003 Buick Lesabre Limited
3.8L V6
Minot, ND
12-15-2008 08:22 PM
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dogman Offline
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Post: #4
RE: rough run open to closed loop
I have planned on replacing the battery. If I leave it disconnected for a few hours while getting new battery, do you think that will be long enough? Car struggles to turn over in the morning even with it in the garage where it's above zero degrees.

Doug
2003 Buick Lesabre Limited
3.8L V6
Minot, ND
12-16-2008 09:19 AM
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colchiro Offline
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Post: #5
RE: rough run open to closed loop
Yeah, we're having similar temps here. Had -25F forecast for last night, but lucked out and only had about -16F. Sure am glad I have a garage.

In your case I'd disable whatever I can to stabilize things for the next week until we get thru this cold spell.

I would think disconnecting the battery for 5 minutes should clear the ecu. Some suggest removing the neg terminal from the battery (always the safest) and connect it to the pos battery terminal to speed up the process.

Bear in mind that a drained lead acid battery will freeze quickly, if subjected to our cold temps for more than an hour or two.

Rick

Links: Documents / Tuning for Mileage | Toyota Sensors | Autoshop Sensor Tutorials
12-16-2008 03:49 PM
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dogman Offline
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Post: #6
RE: rough run open to closed loop
I think I may have found the problem. While driving out on the highway today ( I do alot of it), I thought to myself, I bet the O2 heater wires are fused. Sure enough they are and the fuse was burnt. I started the car and let it run so it would switch from open to closed loop. No hesitation during the switch.

Doug
2003 Buick Lesabre Limited
3.8L V6
Minot, ND
12-30-2008 05:48 PM
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colchiro Offline
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Post: #7
RE: rough run open to closed loop
Yes they're fused, but never heard of anyone blowing one.

In retrospect it does make sense that it would be open loop until exhaust heat finally warmed up the sensor, rather difficult when idling with the winter we've had lately. It's already -19F.Tongue

Rick

Links: Documents / Tuning for Mileage | Toyota Sensors | Autoshop Sensor Tutorials
(This post was last modified: 12-30-2008 08:03 PM by colchiro.)
12-30-2008 07:53 PM
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dogman Offline
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Post: #8
RE: rough run open to closed loop
It may have somehow blown when O2 sensor was changed as the problem arose that same day. 10:45 pm and it is -27F in Minot.

Doug
2003 Buick Lesabre Limited
3.8L V6
Minot, ND
12-30-2008 08:46 PM
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colchiro Offline
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Post: #9
RE: rough run open to closed loop
We only got -24F.

Wahp / Breck got about 11 inches and we got about 6. Heard someone got around 23 inches when I first turned on the TV, but didn't catch who. Going to be an interesting winter.

Rick

Links: Documents / Tuning for Mileage | Toyota Sensors | Autoshop Sensor Tutorials
12-31-2008 05:41 AM
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mrbillr Offline
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Post: #10
RE: rough run open to closed loop
Glad it is you and not me. You are a reminder of why I moved south. I squack if it gets below freezing. A couple weeks ago I had the mower out to mulch the leaves in the yard, where you guys are messing with snow blowers. Burrrrr, you can keep it up there.

MrBill
2008 f250 XLT 6.4 diesel 2x4 automatic extended cab
12-31-2008 12:11 PM
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