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Rough Idle when cold

wolfe

in black sheep's clothing
Jun 2, 2008
17,632
333
Si Oh Em Pee Tee Oh En
Wouldn't it do it all the time regardless of temperature? It ran fine all summer on start up but once it got below 45 degrees it did this. It did it last winter too.

Oh, I didn't know it did it last winter. I was wondering if it was maybe a small one that when it was warmer out didn't cause that much of an issue and now that it's getting colder it is. Hmmm....
 

Turbocharged400sbc

3800 & 4T80E > ALL
TCG Premium
Jun 16, 2007
32,538
15,847
hangover park IL
98 LS1 runs like crap on start up once we dip into these lower temperatures. I just did a tune up on it (Plugs and wires).
It sounds like its missing and surging and sometimes it dies. It does this until the car warms up.
Any idea? Could it be the O2 sensors?
runs like crap in what way surging wise? runs even then starts to surge when in closed loop?
almost like a partial mis? one or multipkle cylinders contributing say 50%?
if surging occurs in closed loop and they are near 50k+ id look at o2sensors soon. typically cold start issues are clogged/streaming injectors that until the fuel rails/fuel and engine get hot the fuel doesnt vaporize well.


since cold, my shitbox has like a dead spot at part throttle while leaving a stoplight, sign, ect... if i go WOT im fine...

i think im just gonna spray it, that should clean it up.

check your tps signal for dropouts esp if its in the same lower sweep of the tps (most of a tps's wear is at the bottom end of the travel)
 

ThirdgenTa

TCG Elite Member
Mar 17, 2008
5,156
140
Aurora
runs like crap in what way surging wise? runs even then starts to surge when in closed loop?
almost like a partial mis? one or multipkle cylinders contributing say 50%?
if surging occurs in closed loop and they are near 50k+ id look at o2sensors soon. typically cold start issues are clogged/streaming injectors that until the fuel rails/fuel and engine get hot the fuel doesnt vaporize well.


It does it for like the first 5 minutes or so. The rpms will jump all over the place. I think the computer senses that it is about to stall and then corrects it and it jumps way up. Sounds like someone is revving it. And like I said, runs like a champ in the summer and when it starts to get cold it runs like shit.
 

ThirdgenTa

TCG Elite Member
Mar 17, 2008
5,156
140
Aurora
Does it "run better" if you give it a few more hundred RPM at idle?


Not really, until it actually warms up.


I tried to get a video of it today. I started it up and I recorded it for about a full minute or so. Then I stopped recording and was about to go inside and it suddenly almost died and the rpms jumped up. Started recording again and it smoothed out.

Here it is with a slightly rough idle but not too bad. I don't think it was cold enough this morning.
http://www.youtube.com/watch?v=/_YvUsL5BPM8
 

ThirdgenTa

TCG Elite Member
Mar 17, 2008
5,156
140
Aurora
So I cleaned the IAC and the MAF. Gonna wait until it's really cold out to see if it's acting up.

Before
20121009_195110.jpg

After
20121009_195501.jpg


MAF
20121009_200637.jpg
 
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