Idle Issues - Chevy Cobalt Forum / Cobalt Reviews / Cobalt SS / Cobalt Parts
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post #1 of 7 (permalink) Old 03-20-2018, 06:21 AM Thread Starter
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Idle Issues

Hey guys! I bought this 2006 Cobalt SS/SC about a month ago. I got it for a pretty fair price as it needed some general things. One thing that needed to be done was exhaust. The car had a complete exhaust, headers back. Some idiot decided that since the gasket was leaking where the exhaust bolted up to the header to weld the flange all the way around (or at least as much as they could reach), and also welded the flanges where the cat back so to speak would bolt up. The cat acted like it had been gutted, or just blown out because I was getting a CEL sometimes about the cat. I don't remember the code, but it was saying the cat was bad.

Anyway, I bought an eBay header and down pipe (catless), long tubes so to speak and got them installed 2 nights ago. My secondary o2 sensor wires were not long enough to reach (it had already been a long night and I didn't feel like extending them), so I had left the plugin where the secondary o2 sensor would go and drove it to work the next day. The car has always had a high idle issue since I got it, and figured part of it was due to the exhaust leaks before the upstream o2 sensor. Anyway, so it still had a high idle after I got the exhaust work done. No big deal, figured has to be something else right?

So last night I extended the wires for my downstream o2 sensor and plugged it in. I drive to work this morning and I notice that when I had my cruise control on, that it seemed to let off the gas a little and pick back up. At first I thought that it was the cruise messing up as I rarely use cruise anyway. So I kicked it off, and even with my foot on the gas it was doing it slightly at times. I glanced up and looked at my wideband, and it would go lean (like you would let off the gas causing a spike lean condition). The idle on the other hand was pretty tame, as it was better than it ever has been (which I thought was weird, because the secondary o2 should only tell the ECM if that cat is good or not right?). EXCEPT, when I came to a stop, after about 15-20 seconds, the car would start chopping at an idle. I could fix it momentarily by reving it up, then another 15-20 seconds it would do it again. I also noticed that when coming to a stop, it would "hunt" for an idle, but then it was fine.

Perhaps hooking up the o2 sensor last night was all a quinkiedink and completely unrelated...Any thoughts? I have 3 different scan tools, Snap-On Modis, Autel MS-906, and a Launch x431. I have not hooked any of them up yet, but they don't always tell you what's wrong either lol.
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post #2 of 7 (permalink) Old 03-20-2018, 10:56 AM
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Yeah, that sounds like a dirty throttle body and leaky intake. If you decide to clean the creosoot make sure the key is out of the ignition or unplug it. Add cleaner to rag and wipe. Do not spray directly onto the plate. Then make sure the intake boot is well clamped.

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post #3 of 7 (permalink) Old 03-20-2018, 11:41 AM Thread Starter
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Back about a week after I got it, I did pull the throttle body off and clean it like you mentioned that and it didn't make a difference. It also wasn't all that dirty. I wondered about the intake gasket leaking as well. Prior to that I had wondered if the TPS inside of the TB was messed up or something along the lines of that, but my percentages seem pretty on point with a monitor.
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post #4 of 7 (permalink) Old 03-20-2018, 12:01 PM
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You'd get a code if it was messed up. Check the short tube between the intake and the valve cover, sometimes it cracks. Are you getting a lean code?

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post #5 of 7 (permalink) Old 03-20-2018, 10:57 PM Thread Starter
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Quote:
Originally Posted by Coby7 View Post
You'd get a code if it was messed up. Check the short tube between the intake and the valve cover, sometimes it cracks. Are you getting a lean code?
Nope. I pulled codes when i got home and I’m getting a p0133 and p1133. I unplugged the secondary o2 and the whole issue with it acting as if you let off the throttle a bit and had a lean spike went away it seemed anyway on my short drive.

I’ve got a catch can and I checked both lines and they are good and tight and not dry rotted.

Just to add info to the high idle issue that I have. What I mean by that is that it idles fine but if I coast in neutral or push in my clutch then it will idle at around 1500 rpm then drop as I’m rolling around 1-2mph at almost a complete stop then it drops down to what it should be.

Last edited by matholland618; 03-20-2018 at 11:11 PM.
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post #6 of 7 (permalink) Old 03-21-2018, 06:17 AM
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I think that was an issue with the 06 SS/SC and was semi normal, some did it worse than others, maybe an owner of one can chime in.

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post #7 of 7 (permalink) Old 03-21-2018, 03:51 PM
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Quote:
Originally Posted by Coby7 View Post
I think that was an issue with the 06 SS/SC and was semi normal, some did it worse than others, maybe an owner of one can chime in.
I did a quick google search (results mostly coming from CSS), and yes, that is definitely the case - they kind of idle all over the place.

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2007 Chevrolet Cobalt LT - M62 Supercharger, Ported Throttle Body, 42 lb/hr Injectors, Intense 2.9" Pulley, Cobra Heat Exchanger, SS/TC Exhaust, TTR Engine and Trans Mounts, Trifecta Tune, ZZP Header and Downpipe, '08+ FE5 Struts/Shocks, SSC Springs, FE5 Control Arms, SS/SC Front Swaybar, Powell Hardcore Rear Swaybar, 18" MSR 045s, Dunlop ZIIs, Nightshaded Tails/Side Markers, Shorty Antenna, Black Bowties, Black Grilles, Black Headlights, Dual JL 12" w1v2 Subs, A/D/S Front/Rear Speakers, Pioneer 7" Touchscreen, G85 Recaros, Leather Rear Seats, 160 MPH Cluster.
2014 Chevrolet Cruze Diesel - 17" MSR 013s, Black Bowties, Black Tails, UR Rear Lower Bar
1981 Chevrolet Camaro Z28 - JVC Ribbon Tweeters, SEAS Mids, Pyle Woofers, Kenwood Tape Deck, Zapco Amp/Equilizer, Ceramic-Coated Longtubes, 2.5" Pypes Stainless Exhaust, Bilstein B6 Shocks, GW U/L Control Arms, Hotchkis Springs Sway Bars, DD HDX Cluster
2017 Chevrolet Volt LT - Black Bowties
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