1999 Chevy Tahoe hard starting /flooding

Tiny
GARY THOMAS
  • MEMBER
  • 1999 CHEVROLET TAHOE
  • V8
  • 4WD
  • AUTOMATIC
  • 197,000 MILES
My truck runs great even when it freezing out but during cold months if I let it sit for 24 hours without starting, it will start cranking fast for a couple of seconds, then real slow like the timing is retarted and spitting thru the throttle body, then fast again. It continues this way throughout the cranking process meanwhile this is flooding the plugs and cylinders real bad so I have to pull and replace them. A couple of times I heated up the plugs and warmed up the throttle body and it fired right up. Could the air temp or other sensors be giving the pcm a wrong reading making it dump fuel( which is at 61#) if so what is the most common sensor to start an engine. Also the battery is fully charged and it never happens in the summer months or when the engine is warm
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Sunday, December 28th, 2008 AT 10:12 PM

7 Replies

Tiny
RACEFAN966
  • EXPERT
I would check the Air Charge Temp Sensor or the Coolant Temp Sensor (not sender). Give me an ohm reading on both sensors and the know temp of the sensor at the time and I will look and see if they are in specs.
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Sunday, December 28th, 2008 AT 10:32 PM
Tiny
GARY THOMAS
  • MEMBER
Outside temps around 40. Air intake sensor 4 volts and 9.14 resistance, engine coolant 5 volts and 7.39 resistance. Engine cold. Thank you for getting back so soon
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Tuesday, December 30th, 2008 AT 1:53 AM
Tiny
RACEFAN966
  • EXPERT
Now you did do the ohms tests with the sensors unpluged and tested the sensor?
If this is true then the Coolant Sensor should have showed 7280 ohms. So it is close I would say it is good.
Now the Air Intake Temp sensor is not in range. It is telling the computer that it is about 10 deg. Colder then it is so I would replace this don't know if this will be the complete fix but it is bad as it should read 7280 ohms too.
After the sensor is replaced let me know how it is doing as we will test the Throttle Position sensor and Mass Air Flow Meter next ok. Thanks and Happy New Year.
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Tuesday, December 30th, 2008 AT 9:45 AM
Tiny
GARY THOMAS
  • MEMBER
I replaced the coolant and air intake sensor with no luck. I did a test on the tps and its working properly. On the maf sensor the volts going to it are good but I cannot test it because it requires a scan tool which I do not have, would that keep it from turning over or just make it run rough. Also I tested the voltage to the crank positioning sensor and the volts were good to it but im not sure how to test it, I unplugged it and tried to turn it over which made it crank great without the cranking going high and low and misfireing but of course it was unplugged so would not start, I would just replace it but they want $88.00 for a new one, how can I test this? Or should I be trying something else. Thank you
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Thursday, January 1st, 2009 AT 2:22 PM
Tiny
RACEFAN966
  • EXPERT
Ok lets do this simple test and answer if it is bad or not. The Mass Air Flow Meter I need you to diconnect it and see if the truck starts. If it starts and runs then the MAF Meter is bad and needs to be replaced. Now it is still don't start do not replace it as with the last sensors the ACT (air charge temp) sensor was the only bad one not both ok. I am trying to help and of we do these tests we will find the problem ok. If all this turns out ok then the Cank and cam sensors wiil the next two to test. After those tests in order to test anything more you will need a scan tool.
Now you said in your last contact that the engine is not turning over? To me that means when you turn the key to try to start it that it does nothing at all. So it the engine turning over when you turn the key to start and the engine is just not starting and running or is it doing nothing at all?
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Friday, January 2nd, 2009 AT 10:00 AM
Tiny
GARY THOMAS
  • MEMBER
The engine cranks fast a couple of turns then slow likes the timing retarding then fast and slow again until the battery dies down. Some times it will spit thru the carb but mostley it dumps alot of fuel in the cylinders fouling the plugs. The battery and starter are new and im also getting good spark. When its cranking it acts like it wants to start but just doesn't
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Friday, January 2nd, 2009 AT 8:21 PM
Tiny
RACEFAN966
  • EXPERT
Did you unplug the mass air flow sensor and try to start it? If not please do and let me know if it starts ok. You have checked the distributor cap and rotor haven't you? Get back to me with this info and we will take it from there.
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Saturday, January 3rd, 2009 AT 9:20 AM

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