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Still stuck on a cobolt

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19 Sep 2019 22:07 - 03 Oct 2019 18:27 #33698 by Tsavory
Still stuck on a cobolt was created by Tsavory
2007 Chevrolet Cobalt 2.2L Eng LT
Codes p0300

Customer complaint smokes bad some times blue some times black sometimes white.

When I first messed with it it would not even Crank hunted down that problem they had some kind of security system that they had bypassed the exciter wire for the starter which was no longer in the car wires just cut.

Got it cranking it would act like it wanted to start but then die checked Ignition, injector pulse, fuel pressure (which is a bit High) thought heck just to see give it a shot of starting fluid it took off ran a few seconds died ok with no throttle control weird . tried again it took off feathered the throttle and it came to life. Idled smooth ran good boss took it for a test drive said it ran great.
the Next morning it did the half start then die BS little SF and off it goes runs great. Turn off and restart no problems.

What I have found is that if I can get it to run for like 30sec it will run great no issues till it sits for a few hours or if I turn it off within 5 min it has to sit about 20 min before acting up.

To me it seems like a air\fuel issue.
All scan data seems good the O2s1 is a little high but not to bad
Now the BARO to me seems way low as I am used to seeing at my Altitude around 29.6 but it shows 3.6 .
Problem with the scan data is I only have about a 30 sec window it acts up.

Oh yeah feathering the throttle about every third try it revs up about 3000 if I really have control(even though Scan data shows I do all the time) i can hold it about 2500 for 10 to 15 sec and it will stay running.

Any ideas on the next step.

I for got to mention fuel pressure readings key on bumps to 55psi initial start 70PSI works down to about 65PSI calls for 50-60psi.
p0300 scan data shows every now and then one 1 and 3 just a couple then none.

Only smoke it first few seconds after it starts a whitish blue. spotted oil in the intake cleaned it out when I cleaned the throttle body and even blocked the port into the intake off in case crank pressure was pushing though adding too much air on startup. No change
Last edit: 03 Oct 2019 18:27 by Tsavory.

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20 Sep 2019 07:51 #33708 by Cheryl
Replied by Cheryl on topic Still stuck on a cobolt
Did you do a throttle body relearn after cleaning it? How’s the spark plug gap?
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20 Sep 2019 08:38 #33709 by Tsavory
Replied by Tsavory on topic Still stuck on a cobolt
Yes I did and the Gap is good .042-.043

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20 Sep 2019 09:18 #33711 by Cheryl
Replied by Cheryl on topic Still stuck on a cobolt
Do the iac and ect agree when cold?

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20 Sep 2019 09:19 #33712 by Cheryl
Replied by Cheryl on topic Still stuck on a cobolt
Iat intake air temp
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20 Sep 2019 21:57 #33732 by Tsavory
Replied by Tsavory on topic Still stuck on a cobolt
I will have to double check that. I did not have time to mess with that one today.

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21 Sep 2019 08:02 #33737 by Chad
Replied by Chad on topic Still stuck on a cobolt

Tsavory wrote: Now the BARO to me seems way low as I am used to seeing at my Altitude around 29.6 but it shows 3.6 .


:ohmy: What altitude ARE you at? A barometer reading of 3.6 In.Hg equates to close to 50,000 ft above sea level.

"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer."

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21 Sep 2019 09:10 #33741 by Tsavory
Replied by Tsavory on topic Still stuck on a cobolt
yeah I am at about 800 ft used to seeing 29.6

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21 Sep 2019 10:29 #33742 by Chad
Replied by Chad on topic Still stuck on a cobolt
I would be looking at your MAP Sensor/Circuit. BARO is calculated from the MAP signal, during KOEO, (and sometimes WOT).

"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer."
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03 Oct 2019 09:37 #33988 by Tsavory
Replied by Tsavory on topic Still stuck on a cobolt
OK finally got a chance to make back to this one.
Different scan tool and the Baro is now reading correctly Map matches it.
Coolant reads 68
Intake air reads 82
AMB air reads 78

it is 76 out right now.

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03 Oct 2019 18:26 #33994 by Tsavory
Replied by Tsavory on topic Still stuck on a cobolt
Also I cant find the spec on a injector bleed test but they are all 50psi to25-26 psi.
Each cold start it has the smell of raw fuel and white smoke.
Which is why I did the injector bleed test.

I have plugged off the valve cover tube to eliminate starting crank pressure build up..
I know I am over looking something simple I have also used the water trick to find a leak but no luck.{i need a smoker lol}
still stuck.

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03 Oct 2019 18:33 #33995 by Cheryl
Replied by Cheryl on topic Still stuck on a cobolt
Maybe the white smoke is coolant?? Maybe try put a coolant pressure tester in the cooling system leave a few hours see if coolant gets in any cylinder
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03 Oct 2019 18:44 #33996 by Tsavory
Replied by Tsavory on topic Still stuck on a cobolt
I will try tomorrow but I doubt that is it since I have not lost any coolant in 3 weeks I let it run about 2 hrs today to build up battery. Other than that and a few I knew it was not it tests its been sitting.
I guess it could have a head gasket that don't leak when cold but will during cool down period.
So first thing Ill put pressure gauge on let sit a few hrs then Ill start let it get up to temp and re test Ill pull plugs and bore scope the cylinders after the cool down.

While at it any other suggestions? I need this one gone LOL.

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03 Oct 2019 18:49 #33997 by Tsavory
Replied by Tsavory on topic Still stuck on a cobolt
One more thing this evening I noticed it tended to have random misfire for a bout the first 5 min. and erratic idle the first time its done that.

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04 Oct 2019 03:15 #33998 by ptebo1
Replied by ptebo1 on topic Still stuck on a cobolt
Take a fuel sample. Maybe its got bad gas...

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04 Oct 2019 14:06 #34002 by Tsavory
Replied by Tsavory on topic Still stuck on a cobolt
Pulled plugs cylinders dry as a bone.got it started let it get to temp pulled plugs again bore scoped it stayed dry. so not a coolant leak in the cylinders.

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04 Oct 2019 20:02 #34009 by BrandonF
Replied by BrandonF on topic Still stuck on a cobolt
I hope you get her handled brother. Sometimes they'll get you like this. When this happens to me I have to stop...back up, and figure out which road I need to go down. If your thinking it's something wetting the plugs, pick a system, fuel or coolant....like you did. Inspecting the cylinders like you did is just fine, but you may also try putting her under pressure and rechecking. Possibly even pulling the plugs before you go home, put her under pressure, and let her sit over night, then check it in the morning. On the fuel side of things. You can keep the fuel system primed, and keep your eyes glued back and forth in each cylinder. Doing a bleed down test was a smart thing to do. But keep in mind, a couple, few, or even several drops in a cylinder can wet that plug and get you a long start but give you somewhat similar injector bleed down numbers. I had an Altima a couple of months ago that was like that. And I was luckily enough to not have to remove the fuel rail to inpect it. I was able to catch it dripping into the cylinders. Good luck my friend.
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