Rough cold starts

Lownslowlsc

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She has the tendency to idle roughly upon first startup when it's <10-15 degrees outside. Happens anywhere from a minute to 3 depending on how cold it is. If put in reverse during that time to back out of my spot it'll die or come very close. Once it's put in D and driving (If it doesn't die) there is no noticeable misfires. It also sometimes dies within 5 seconds after the first startup and then it'll continue idling rough as described above.

No check engine lights and no misfires while driving. It did do this last year as well but to a lesser extent.


What's the deal?
 
When I had this problem it turned out half my throttle body gasket was missing. New gasket, didn't stall out in the cold anymore.
 
When I had this problem it turned out half my throttle body gasket was missing. New gasket, didn't stall out in the cold anymore.

I was thinking something of that nature, maybe even an iac valve or a cracked vacuum line somewhere. At 160k anything's possible.

It's supposed to be a balmy 27 degrees tomorrow so hopefully i'll be able to look it over. Thank you.
 
what maintenance have you done recently?
plugs maybe? or maybe not and that's the problem?

vacuum leak is possible too.
can you data log? any of the fuel trims way off?
 
what maintenance have you done recently?
plugs maybe? or maybe not and that's the problem?

vacuum leak is possible too.
can you data log? any of the fuel trims way off?

Plugs were done about 20k ago with Al Double plats. No data logging available att. I'm just trying to figure out why it would idle so badly at start up but drive completely normal 30 seconds later when it would normally still be sputtering at idle..
 
I have similar issue and when my engine runs at normal temps it runs great its just at start up when engine is ice cold is when it dies and or stumbles to idle. I have narrowed my problem to one or more of the following: plugs, air pocket in coolant system, thermostat stuck in open position, coolant temp sensor, air temp sensor or IAC. I am going to change my plugs next week because they have 90,000 + on them and remove air pocket in coolant system today. My gut is telling me the plugs are the at core of problem with one of the other things i mentioned being secondary issue.
 
I noticed that when it was really cold out that one of the two vacuum hoses (On top of the manifold @ the T, connects to pcv) looked to be completly collapsed at the bend . I replaced one years ago due to a rip but left the other as it was.

Is it at all possible that caused the rough idle/start issue? Since replacing the other one it hasn't acted up last two days with the temp between 7-10 degrees @ morning start up.


what maintenance have you done recently?
plugs maybe? or maybe not and that's the problem?

vacuum leak is possible too.
can you data log? any of the fuel trims way off?

I've monitored the fuel trims via the bafm obd2 dongle and both banks appear to be the same/steady. The 02s appear good with the exception of B2S2 which is a bit lazy/late to turn on. I honestly have to do more investigating on that particular sensor.

No cel but did get some Mode 6 faults that revolve around egr/air. $41 is EGR $30 is AIR.

---------------
TID $30 CID $11

Max:512
Current:826

*Voltage for upstream flow test and rich limit

--------------
TID $30 CID $12

Max:512
Current:65,535

-------------

TID $41 CID $11

Min: 63,616
Current:210

*This could be due to a downstream DPFE hose, maybe linked to the EGR. Could possibly an O2 sensor.

--------------

Not sure why these two Cyl misfire related codes are popping up..

TID $51 CID $09

Max:1,442
Current: 65,535

TID $51 CID $0a

Max: 1,442
Current:65,535

--------------


I have a feeling the above M6 codes are egr/02/Cat related.

I haven't retested since replacing the hose.
 
Crap, this was supposed to be inserted above...

Edit: -5 out this morning and it still hasn't done it. I still don't understand how one collapsed vacuum line from intake to pcv could cause it to act the way it did. But so far *Crosses fingers* that seems to have fixed the rough cold start/idle issue in <10-15 degree weather.
 
The PCV is a metered air circuit. If the hose collapsed enough to restrict flow, it would upset the A/F mixture, particularly when cold and especially at idle.
 

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