After exhaust install: High idle, etc.
07-02-2008, 01:12 PM
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After exhaust install: High idle, etc.
Ok so i installed my xtc dp with cat and the gmpp exhaust. Car threw a CEL. Diconnected battery, CEL went away for a day now its back. Problem is the car idles at 950rpms and when i come up to a stop and put it in neutral the rpms spike to about 1500 then go back down... Never had a problem when i did the intake, but the exhaust seems to be messing with the car. Any suggestions before i book it in?
My understanding is the reason for the CEL is the extra emmissions going through to the O2 sensor are messing it up. But this shouldnt cause an idle spike should it?
My understanding is the reason for the CEL is the extra emmissions going through to the O2 sensor are messing it up. But this shouldnt cause an idle spike should it?
07-02-2008, 06:13 PM
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Ok so i installed my xtc dp with cat and the gmpp exhaust. Car threw a CEL. Diconnected battery, CEL went away for a day now its back. Problem is the car idles at 950rpms and when i come up to a stop and put it in neutral the rpms spike to about 1500 then go back down... Never had a problem when i did the intake, but the exhaust seems to be messing with the car. Any suggestions before i book it in?
My understanding is the reason for the CEL is the extra emmissions going through to the O2 sensor are messing it up. But this shouldnt cause an idle spike should it?
My understanding is the reason for the CEL is the extra emmissions going through to the O2 sensor are messing it up. But this shouldnt cause an idle spike should it?
07-03-2008, 09:02 AM
#3
If you are still having the problem try clearing the DTCs with a scan tool. Disconnecting the battery DOES NOT reset the learn values of the H02S sensors. There is a notice in the factory service manuals about replacing the H02S sensors (pulling them out and reinstalling them does the same thing) it says you need to clear DTCs -- even if you don't have them -- to reset the learn values. Since the ECM has its' own power source, disconnecting the battery does not clear the codes or reset the learn values.
07-04-2008, 09:06 PM
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i had a prob when i install my high flow cat , it was saying bank threshold to high or something like that and that was because i didn't have a obd2 cat, i do now. but i do have problems with my revs going to 1500 and sometimes 3000 when i stop in gear or in neutral, i have a automatic to.
07-05-2008, 11:40 AM
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Hm sounds similar to my issue but mines worse than yours. Looks like I need to replace the first O2 sensor to see if that my issue
https://www.cobaltss.net/forums/problems-service-maintenance-69/misfire-all-cylinders-post-header-leak-fix-wtf-116911/
https://www.cobaltss.net/forums/problems-service-maintenance-69/misfire-all-cylinders-post-header-leak-fix-wtf-116911/
I had a small leak near my #4 primary on my header top far driver side bolt. Got together with a buddy and we went thru each bolt 1 by 1 to find it. Great, no more leak..... BUT! Now I have a sporadic idle and misfires in all four cylinders. 
I just replaced my O2 sensor last summer before my warranty expired, but that is the only thing I can think of. HPT scans show my O2 B1S1 as a flat line, then a jump high, then a dive low, long flat line, repeat as opposed to the normal peak and valley rhythm. My low end timing is running 20-25* when the tune is commanding teens and nothing on the tune has changed, even reflashed it to be safe. I'm tired of ******* with the car today, but anyone have any other ideas before buying my 4th 02 sensor? It's just ironic how I fix my leak and now I have this.
If it's not one thing it's another with this car lately.
I just replaced my O2 sensor last summer before my warranty expired, but that is the only thing I can think of. HPT scans show my O2 B1S1 as a flat line, then a jump high, then a dive low, long flat line, repeat as opposed to the normal peak and valley rhythm. My low end timing is running 20-25* when the tune is commanding teens and nothing on the tune has changed, even reflashed it to be safe. I'm tired of ******* with the car today, but anyone have any other ideas before buying my 4th 02 sensor? It's just ironic how I fix my leak and now I have this.If it's not one thing it's another with this car lately.
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