I Think I Broke It... - Chevy Cobalt Forum / Cobalt Reviews / Cobalt SS / Cobalt Parts
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post #1 of 11 (permalink) Old 01-02-2010, 04:45 PM Thread Starter
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I Think I Broke It... UPDATE

Long story but let me tell it...

For Christmas my girl got me one of the spectra intake tubes from autozone (not the modular one, but the solid one that is cut to fit) and a 90* rubber coupling from Napa. Well, I got it on there, looks great, Works Awesome, but the problem, my engine bay looked dirty with the shiny new intake in there.

I went to autozone, got some Engine Foaming Degreaser/Cleaner and a can of STP Throttle Body Cleaner (noticed the throttle body was in needing of a bad cleaning)

So, I get home, cleaned the throttle body according to directions, and then started it up... no problems, Then I shut it off, and use the foaming degreaser/cleaner. Engine was cool, like can said it should, so I sprayed it on, being careful not to get anything on any of the connectors, just did the engine, and engine bay, and I wiped anything that had electrical connectors close by...

Let it sit for 15 min, like the can said to. Rinsed, and then started it up to let idle dry for 10 minutes. Everything is fine...

Here is the kick in the nuts now...

I took it around the block, and everytime I let off the gas and pulled it out of gear, the RPMs stayed around 1500-2000rpm. NO CEL, No rough Idle, just seemed to want to run high...

Been messing with it for about an hour now, and It seems to be everytime I shut it off, turn the key, pump the throttle, then crank it up but not get on the throttle, the idle comes right back down to normal. BUT! when I tap the throttle, she revs to 1500 and stays there!

WTF?!?!?!?!

I checked everything Possible- Connections, The One Vacuum Line, Wires, Nuts, Bolts, Intake, Oil, Coolant... Everything is NORMAL.

And there is no CEL light on.

Other than the high idle, the thing runs and drives like it always has, GREAT!, I just now have a mysterious high Idle, that has come out of no where. I have come to the conclustion that it isn't the cleaners I used, just a freak coincidence.

Any Suggestions???

Steven

Edit* Checked Alternator Voltages too, and Battery Voltages, all is normal...

Last edited by G5Steven; 01-03-2010 at 04:48 PM. Reason: update
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post #2 of 11 (permalink) Old 01-02-2010, 04:48 PM
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dirty throttle body could have messed with the throttle position sensor.

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post #3 of 11 (permalink) Old 01-02-2010, 04:48 PM Thread Starter
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Quote:
Originally Posted by ff_drift_lol View Post
dirty throttle body could have messed with the throttle position sensor.
Say What?
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post #4 of 11 (permalink) Old 01-02-2010, 05:11 PM
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Did you force the throttle blade open at all when cleaning the TB? Idle is controlled by the throttle blade on drive by wire so you need to be careful.
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post #5 of 11 (permalink) Old 01-02-2010, 06:20 PM Thread Starter
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Yeah, but I was careful about it... could that have thrown off the throttle position sensor?

---------- Post added at 09:20 PM ---------- Previous post was at 08:31 PM ----------

so, I still have like 27k left on my warranty, I guess its off to the shop this coming weekend
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post #6 of 11 (permalink) Old 01-02-2010, 09:24 PM
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yea. take everything apart again(throttle body wise) and take a look and make sure everything is in the right place/snug. def make sure nothing is stuck in there also.

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post #7 of 11 (permalink) Old 01-03-2010, 09:24 AM Thread Starter
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Already did that, but I didn't get to the actual guts of the thing, I just cleaned the opening...
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post #8 of 11 (permalink) Old 01-03-2010, 12:37 PM
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when the throttle body is dirty you'll get a rough idle because the pcm is constantly trying to correct the position of the valve. i've been throwing a tps code cause my battery is shot (not exactly sure why it does this) and the idle will float around 1500 rpm when coming to a stop in neutral. i'm no expert but i am assuming that the constant correction of the throttle body position could throw off the sensor. it may be out of whack instead of just not working and throwing a code. there's voltage tests you can do to check, but I am not sure of the voltage range that the tps operates at. most sensors are 0-5 volts. it's safe to assume as the throttle body opens, the voltage will rise. just to be clear I'm not even sure this is the answer to your problem, but it very well could be.

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post #9 of 11 (permalink) Old 01-03-2010, 12:47 PM


 
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try checking maf sensor make sure its not dirty
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post #10 of 11 (permalink) Old 01-03-2010, 02:41 PM Thread Starter
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UPDATE:

After driving around CFL for the day, the idle slowly came back to normal when driving, it started out like yesterday being high, but after an hour of driving, it came down to being about 1500rpm or lower, then slowly came down at a stop, and after a bit more driving, it came down to where it used to be. I'm guessing the TPS, and the Computer had to readjust after cleaning off an 1/8" of carbon soot from the throttle body opening and butterfly valve.

Now I start it up, goes immediately to 1000rpm and then drops to normal operating temp idle of 750rpm, and then coasting to a stop it is a slow drop from 1500rpm to 750, just like before the cleaning.

Conclusion to my dilemma, Don't go more than like 10k miles between throttle cleanings, or you will have the erratic idle of a TPS and Computer that can't remember what a clean Intake was...
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