Chevy Tahoe engine problems

Tiny
BOSTONMANIAC781
  • MEMBER
  • 1999 CHEVROLET TAHOE
  • V8
  • 4WD
  • AUTOMATIC
  • 192,000 MILES
After replacing my starter on my 99 tahoe, when I started it, it revved real high then went back down and died. It did this a few times then I kept it running by pumping the gas. It ran very rough and was smoking and blowing some sparks out of the exhaust. After shutting it down, I noticed the exhaust system was glowing hot. Could it be the plugs? I had bosch platnums in it and I read that Bosch don't go good with Gm cars. I just went and picked up some ac delcos that I'm gonna put in tomorow.
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Thursday, December 30th, 2010 AT 1:36 AM

14 Replies

Tiny
MERLIN2021
  • EXPERT
You may have had a bit of unburned fuel in the exhaust and or crankcase, especially if you where cranking it for a while? Pull oil dipstick and check the level and smell if gas mixed in ther. If it did, you need to change the oil and filter, and check the catalytic converters on the truck, this can destroy them!
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Thursday, December 30th, 2010 AT 1:46 AM
Tiny
BOSTONMANIAC781
  • MEMBER
Alright thank you so much for your answer. Ya we were turning it over for quite a bit until the starters finally gave out. My dad was saying that there could have been a lot of unburied gases that were being burns in the exhaust instead of in tue actual motor. Again thank you. Hopefully it doesn't ruin the cats, I just replaced both of them 6 months ago and I don't think the warranty covers them if they get ruined from unburied gases.
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Thursday, December 30th, 2010 AT 2:45 AM
Tiny
MERLIN2021
  • EXPERT
DO NOT forget the oil, or the cats will be the least of your problems!
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Thursday, December 30th, 2010 AT 3:18 AM
Tiny
BOSTONMANIAC781
  • MEMBER
So after I check the oil, ill probly just change it anyway it due for a change I'm gonna put the new ac delco spark plugs in( I read that ac delco are made by Gm and so they are the best spark plugs for chevy motors) and run the car and see if it's better. What should I do if it doesn't fix it? I hooked it up to the code scanner and now it's giving a p0101 and p0108 which I think have to do with the air flow. Could the oxygen sensors or mass air flow sensor be responsible for the motor to act that way?
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Thursday, December 30th, 2010 AT 3:47 AM
Tiny
MERLIN2021
  • EXPERT
Yes, do you have a K&N air filter oil soaked? These are a know problem for the MAF sensor, and WILL screw it up over time, I did a buddy's truck a few weeks ago, and whe I removed the air filter, the MAF was growing a beard. Replaced it along with plugs(iridium) and it ran like a top, he had no codes showing. 101 is the maf code 108 is MAP code, so check for vacuum leaks to! Get a can of spray Throttle body cleaner, start the car and spray around, pay attention to vacuum lines and manifold, if the idle changes, you found a leak. You want the engine running and spray on the outside but do direct the stream onto the hoses, if it is a vacuum leak, the engine idle will change speed, then you have detected a leak, repair the vacuum leak and see how it runs!
Keep the spray away from the exhuast manifolds. Fire hazard. Clean out the TBI with the cleaner while your at it!
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Thursday, December 30th, 2010 AT 4:22 AM
Tiny
BOSTONMANIAC781
  • MEMBER
No I don't have a K and N, I've been thinking about getting one but would you advise against it. I checked the MAF sensor and it's nice and clean, I'll check for leaks though. I took a peek inside the throttle bottle and it looked pretty dirty, it seemed as though there was like a gunky build up in there, is that bad?
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Thursday, December 30th, 2010 AT 4:36 AM
Tiny
MERLIN2021
  • EXPERT
With the engine off, get a rag and throttle body cleaner spray that is sensor safe(crc). Clean out the tbi real good, Gunk is the enemy!
I do recommend against oil soaked air filters, and so does GM! MAF can look clean and still be out of range, a scan tool that reads live sensor data will help here. Maf testing: On GM MAF sensors, there's a couple of quick checks you can do for
vibration-related sensor problems. Attach an analog voltmeter to the
appropriate MAF sensor output terminal. With the engine idling, the
sensor should be putting out a steady 2.5 volts. Tap lightly on the
sensor and note the meter reading. A good sensor should show no change.
If the analog needle jumps and/or the engine momentarily misfires, the
sensor is bad and needs to be replaced. You can also check for
heat-related problems by heating the sensor with a hair dryer and
repeating the test.
This same test can also be done using a meter that reads frequency.
The older AC Delco MAF sensors (like a 2.8L V6) should show a steady
reading of 30 to 50 Hz at idle and 70 to 75 Hz at 3,500 rpm. The
later model units (like those on a 3800 V6) should read about 2.9
kHz at idle and 5.0 kHz at 3,500 rpm. If tapping on the MAF sensor
produces a sudden change in the frequency signal, it's time for a
new sensor.
On the GM hot film MAFs, you can also tap into the ALDL data stream
with a scan tool and read the sensor's output in "grams per second"
(gps) which corresponds to frequency. The reading should go from 4
to 8 gps at idle up to 100 to 240 gps at wide open throttle.
Like throttle position sensors, there should be smooth linear transition
in sensor output throughout the rpm range. If the readings jump all
over the place, the computer won't be able to deliver the right air/fuel
mixture and driveability and emissions will suffer. So you should also
check the sensor's output at various speeds to see that it's output
changes appropriately. This can be done by graphing its frequency
output every 500 rpm, or by observing the sensor's waveform on a scope.
The waveform should be square and show a gradual increase in frequency
as engine speed and load increase. Any skips or sudden jumps or
excessive noise in the pattern would tell you the sensor needs to be
replaced.
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Thursday, December 30th, 2010 AT 4:46 PM
Tiny
BOSTONMANIAC781
  • MEMBER
Well we figured out what it was. It was the brake booster vacuum line. Who would have thought that a simple vacuum line could cause such a problem with the motor. The things starts so nice now with the new starter and runs beautiful with the new plugs.
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Thursday, December 30th, 2010 AT 10:25 PM
Tiny
MERLIN2021
  • EXPERT
Glad we could help, Good work!
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Friday, December 31st, 2010 AT 4:37 PM
Tiny
MERLIN2021
  • EXPERT
What part of Boston are you from? I'm in Brockton?
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Friday, December 31st, 2010 AT 4:40 PM
Tiny
BOSTONMANIAC781
  • MEMBER
Wow what small world, I live in Weymouth.
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Friday, December 31st, 2010 AT 5:03 PM
Tiny
MERLIN2021
  • EXPERT
Yes it is, Have a happy new year!
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Friday, December 31st, 2010 AT 8:58 PM
Tiny
BOSTONMANIAC781
  • MEMBER
Thanks for your help and happy new year to you too!
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Friday, December 31st, 2010 AT 10:33 PM
Tiny
MERLIN2021
  • EXPERT
OK Thanks!
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Sunday, January 9th, 2011 AT 1:30 PM

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