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Car Forum / GMC Cars / April 2008Quad 4 Closed Loop Question
My car generally runs good. A problem is that sometimes, about a minute after a cold start, it will stumble for a few seconds. Usually I'll be in a parking lot or in the driveway so it is not much of an issue. Last week it happened after I pulled into traffic. A scan tool shows that it goes into closed loop about a minute after a cold start (40 deg F.). It cycles back to open loop then closed several times before it stays closed. This happened before the O2 sensor reached .5 volts. I think that this might be a clue to the problem. Once running hot, the O2 sensor will cycle from rich to lean several times a second. My question is what allows the engine to go into closed loop? Thanks Coolant temp and the temp of the O2 sensor, late model obd11 engines have a heated sensor, no mention your year though. > My car generally runs good. A problem is that sometimes, about a minute > after a cold start, it will stumble for a few seconds. Usually I'll be in [quoted text clipped - 13 lines] > > Thanks ----== Posted via Pronews.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.pronews.com The #1 Newsgroup Service in the World! >100,000 Newsgroups ---= - Total Privacy via Encryption =--- 1995 Grand AM. It is not a heated sensor. I think that the coolant temp was not more than 80 deg. F since it had been running less than a minute before going into closed loop. I'll check tomorrow. As mentioned, the O2 voltage had not reached .5 volt so it should not have been hot enough to work yet. This is assuming that open loop is running rich and not lean not allowing it to reach .5 volts. What should the coolant temperature be? > Coolant temp and the temp of the O2 sensor, late model obd11 engines have a > heated sensor, no mention your year though. [quoted text clipped - 19 lines] > http://www.pronews.com The #1 Newsgroup Service in the World! >100,000 Newsgroups > ---= - Total Privacy via Encryption =--- Well we could have skipped the heated sensor issue with having known the year, but as it frequently occurs on these groups, no year mentioned, anyway, the o2 sensor generates it own voltages as the sensor heats up and reacts to the amount of 02 in the exh. stream. Open loop is rich, the .5 volts is default for the pcm to operate from,till the sensor heats up and coolant temps come up. > 1995 Grand AM. It is not a heated sensor. > I think that the coolant temp was not more than 80 deg. F since it had [quoted text clipped - 37 lines] > Newsgroups >> ---= - Total Privacy via Encryption =--- ----== Posted via Pronews.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.pronews.com The #1 Newsgroup Service in the World! >100,000 Newsgroups ---= - Total Privacy via Encryption =--- Any codes showing up? As was mentioned check the coolant sensor. It can be monitored on the OBDII tester. > My car generally runs good. A problem is that sometimes, about a minute > after a cold start, it will stumble for a few seconds. Usually I'll be in [quoted text clipped - 13 lines] > > Thanks No codes. > Any codes showing up? As was mentioned check the coolant sensor. It can be > monitored on the OBDII tester. [quoted text clipped - 16 lines] > > > > Thanks |
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