Brief sputtering on cold startup
09-07-2017, 01:36 PM
#1
Brief sputtering on cold startup
I have an intermittent starting issue with my Cobalt. Sometimes when I go to start it will fire up but is clearly missing on one cylinder for a while and if I try to rev it up a bit it sounds like a Subaru. It will just kind of stutter along until the missing cylinder starts to fire and then it is fine from there on out. It could be head related because I also had this issue before my rebuild but at that time I attributed it to a head gasket leak. I though coolant was leaking into the cylinder while it sat and then misfired on startup until the coolant was cleared. Now that it is doing it again I am not so sure of the cause. I have done searching online and apparently it is a fairly common issue on Cobalts. I saw forums from 2006 with pretty much new cars that had this issue and dealerships told them it was fine. In fact I read about this problem in about 10 different threads but not a single one confirmed any diagnosis or what to do to fix it. Would like to hear your ideas on this.
09-07-2017, 04:23 PM
#2
I've got a bov setup in mine and for a while it started fine but after some time of having it it started kind of sputtering like you said and it would stall if I didn't give it gas. Once it warmed up it was fine. My tuner turned off the turbo spool on start up and that seemed to fix the issue...although after about 5 seconds it sputters again and I give it a bit of gas and it's fine lol.
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jdbaugh1 (09-08-2017)
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jdbaugh1 (09-08-2017)
09-08-2017, 01:21 PM
#5
If coolant was getting into my cylinders wouldn't combustion gasses get into my coolant and I could use one of those test dye kits? Or do sometimes head gasket leaks act like a check valve and seal one direction while allowing flow in the other? My coolant system definitely holds pressure for a long time. It can set for days and then when I release the cap it makes that whooshing sound when the pressure equalizes. Also no white smoke at all which you would think there would be at least a couple puffs right when it starts to fire. Will look into it though. If it is leaking it has to be that something is off with my head. I will look into it though.
09-08-2017, 01:52 PM
#6
Senior Member
iTrader: (6)
A quick easy check for combustion gases in the coolant system, with a cold engine and coolant system start the car and rev it up to 2000-2500 for about 30seconds then pop the coolant tank cap if there is pressure you have combustion pressure reaching the coolant system.
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jdbaugh1 (09-08-2017)
09-08-2017, 03:04 PM
#10
Cold start-up is much richer.... You don't gap for the first 30 seconds of open loop run time.
Did your tuner also tune for open loop? A local cobalt owner on this forum paid $500.00 cash for his tune and they didn't touch the open loop start up trim. It runs like **** until it goes into closed loop and starts adjusting based on the O2.
Did your tuner also tune for open loop? A local cobalt owner on this forum paid $500.00 cash for his tune and they didn't touch the open loop start up trim. It runs like **** until it goes into closed loop and starts adjusting based on the O2.
09-08-2017, 03:12 PM
#11
About the plugs I was just simply wondering if it had any affect on startup. Not going to gap my plugs differently for a smoother startup.
I can't say for sure but I am going to guess he did since my car wouldn't even start and stay running with the new cams at first. It is definitely rich though I would say because startup is accompanied by the smell of gas.
I can't say for sure but I am going to guess he did since my car wouldn't even start and stay running with the new cams at first. It is definitely rich though I would say because startup is accompanied by the smell of gas.
09-08-2017, 03:22 PM
#12
I don't know how cold your mornings are but were at 60F-65F right now. My start-up prior to CL runs in the 11's -12's . A properly tuned OL engine will start good, idle good and should have no change in idle when it goes into CL. If your engine makes a noticeable change in idle (for the good) when it switches to CL, OL mode is not properly tuned.
09-08-2017, 04:22 PM
#13
Senior Member
iTrader: (6)
Cold start-up is much richer.... You don't gap for the first 30 seconds of open loop run time.
Did your tuner also tune for open loop? A local cobalt owner on this forum paid $500.00 cash for his tune and they didn't touch the open loop start up trim. It runs like **** until it goes into closed loop and starts adjusting based on the O2.
Did your tuner also tune for open loop? A local cobalt owner on this forum paid $500.00 cash for his tune and they didn't touch the open loop start up trim. It runs like **** until it goes into closed loop and starts adjusting based on the O2.
10-09-2017, 11:58 AM
#14
Update on this issue. I am running heat range 7 iridium spark plugs. When I daily drive the car 10 miles back and forth to work I do not think I am allowing things to get hot enough for that heat range of plugs to self clean and over time this causes brief startup misfires. New plugs completely eliminate the issue. Also if I have the issue, I can go on a longer interstate drive (2 hours) to an autocross event and run it hard and the startup issue will also go away for a while like the plugs got hot enough to self clean. Not sure on a permanent solution yet. I think hotter plugs would work better for daily driving but not sure if I may need the colder plugs for when I run it hard.