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3.1 engine problem please help
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mike zieman
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Sep 27, 2010, 5:57 AM
Post #1 of 14
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3.1 engine problem please help
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i have a 1991 pontiac 6000-le engine will start and drive for ablock or so puffs out black smoke then dies fuel pressure is 40- 50 psi somebody told me fuel injecters 3.1 engine new intake gaskets recently 4 months ago ran fine till monday started bogging down gave it gas then it ran fine all week till thursday started it up saturday ran fine tried to drive it to the mechanic shop drove about a block puffed out black smoke then died now it wont stay running
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Tom Greenleaf
Ultimate Carjunky
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Sep 27, 2010, 6:31 AM
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Re: 3.1 engine problem please help
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A guess and maybe: There's a sensor that tells it what the engine coolant temp is for computer to determine how much fuel to deliver called a CTS. That's not for a gauge or for fans. If it thinks it's always a cold engine it will dump extra fuel if failed in that mode. Black out tailpipe is about certainly too much fuel delivered.
Early for dependable code reading help but I'd try anyway to get codes,
T
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mike zieman
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Sep 27, 2010, 6:39 AM
Post #3 of 14
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Re: 3.1 engine problem please help
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read the codes o2 sensor lean
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Hammer Time
Ultimate Carjunky
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Sep 27, 2010, 6:40 AM
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Re: 3.1 engine problem please help
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Is your check engine light coming on?
I'm sure it likely is so have the codes read before going any further? We need the exact code numbers.
Do you know the reason that the injectors were changed?
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
(This post was edited by Hammer Time on Sep 27, 2010, 6:40 AM)
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mike zieman
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Sep 27, 2010, 10:31 AM
Post #5 of 14
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Re: 3.1 engine problem please help
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the injectors have not been changed i tested them four of them read 13 one at 10 one at four would that make the car stall i can get the car to run fine sometimes by manually increaseing the throttle seems to run fine then for a minute or two then stalls again dtc code 44
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Hammer Time
Ultimate Carjunky
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Sep 27, 2010, 10:51 AM
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Re: 3.1 engine problem please help
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Black smoke doesn't jive with lean exhaust. You probably should have the O/2 sensors tested to find out if they are reading correctly. They could be clogged up from long term rich mixture.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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mike zieman
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Sep 27, 2010, 12:44 PM
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Re: 3.1 engine problem please help
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what about the injectors
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Hammer Time
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Sep 27, 2010, 1:10 PM
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Re: 3.1 engine problem please help
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What about them? You first have to determine what's really going on with the mixture and reporting
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Sidom
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Sep 27, 2010, 8:33 PM
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Re: 3.1 engine problem please help
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Those are 12 ohm injectors. 10 ohms is borderline drivabililty.
If you've got one at 4 ohms, that needs to be replaced before running any more tests. As long as you're in there, change out the 10 ohm one as well......
I won't go into the big long explantion but a misfire a lot of times will set a lean code.... You would think a rich code because of the misfire but most of the time, it's the exact opposite.....
(This post was edited by Sidom on Sep 27, 2010, 8:37 PM)
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speed
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Sep 27, 2010, 8:39 PM
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Re: 3.1 engine problem please help
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wow 2 ohms make a driveability issue! thats crazy that something as small as 2 ohms can have such a huge affect! just taking notes 
GM ASEP 26 SCC Milford ASE certified in Brakes and Electrical on Thursday April 5th 2012
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Sidom
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Sep 27, 2010, 8:47 PM
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Re: 3.1 engine problem please help
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Actually 2 ohms is borderline, it could go either way. I've seen them that far out with no problems but that much could also affect the pulse width so it really needs to be looked at and compared to the complaint.
One at 4 ohms it too far out, no question it needs to be changed.....
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speed
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Sep 27, 2010, 8:50 PM
Post #12 of 14
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Re: 3.1 engine problem please help
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mama always says better safe than sorry
GM ASEP 26 SCC Milford ASE certified in Brakes and Electrical on Thursday April 5th 2012
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Hammer Time
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Sep 28, 2010, 2:34 AM
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Re: 3.1 engine problem please help
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Has anyone determined why he's getting lean codes?
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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DanD
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Sep 28, 2010, 7:59 AM
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Re: 3.1 engine problem please help
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I agree find the cause of the lean code and it will likely cure the over fueling and black smoke.
I know it doesn’t make sense; how can an O2 be telling the computer its lean when you can see the black smoke of an over fueled engine?
The best way I can explain it is an O2 sensor is just that; it only reacts to oxygen not hydrocarbon (raw fuel), carbon monoxide (incomplete combustion of air/fuel mixture) or any other kind of gas, just oxygen.
Yes it could be an injector issue that is flooding out a cylinder causing it to misfire or a number of other things that will or could cause an O2 sensor to latch lean. Things like the ignition system, engine mechanical, the electronics or a combination of all?
For example; a cylinder begins to misfire (for whatever reason), the fuel along with the oxygen will be pumped out of the cylinder un-burnt. The O2 sensor reacts to all this oxygen and sends out a lean signal (low voltage Approx 1-200 millivolts) to the ECM. The ECM then attempts to get the O2 sensor to toggle rich (800 + millivolts) by opening up the injectors pulse width (injector on time) to all cylinders. So now you don’t just have the one cylinder misfiring; you also have all cylinders receiving too much fuel.
What you should try and figure out is whether the O2 is actually seeing excessive oxygen or has the O2 sensor up and died and can only flat line a low voltage. In other words does the ECM have fuel control or is there an external of the electronics causing the rich mixtures?
As for where, who and what to start testing; every case is different and we may lead you on a wild goose chase by making assumptions, sitting here at the key board and not having accurate data to analyze.
Dan.
Canadian "EH"
(This post was edited by DanD on Sep 28, 2010, 8:04 AM)
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