Question about 1999 Chevrolet Tahoe

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Mass air and throttle position

I actually had one of those mass air bypass resistor (the one thats supposed to get you 10% more horsepower) for the last 15 monthes. so that was the first thing i checked by just reattatching it to the sensor. i dont know how to work the obd (never had the owners or haynes manual) so not sure about the throttle position sensor. gonna pull the fuel filter in the morning.

original:
while pulling out of a parking lot my 99 tahoe died. i tried to start it and it wouldnt , it actually felt as if it were out of gas. i pushed it forward 3 feet so it was level and it started fine. i pulled across the road to an alleyand it sputtered and died again. it took a friend about twenty minutes to get some gas to me(my guage is kinda wonky so i had to try. it started right up and and i drove to the station and put a few gallons in. i then drove the 10 miles back to my house but when ever i tried to give it over 1/3 throttle it had no pick up but it didnt die. when i pulled in to my drive way and parked, it was idleing smoothly and i shut it off and restarted it. it was fine forabout 15 seconds and then it dropped to a barely functioning idle. when i gave it gas it dropped down as low as possible and no amount of throttle feathering would get it to rev up and it died after about thirty seconds. it wouldnt start again and after sitting for about 2 minutes it started right up and ran fine for 30 seconds so i shut it off and restarted it. it ran fine for 10 seconds and then repeated the no rev and then die thing all over again till it died. after a couple it started right up fine again. what the heck man i gotta have this truck or i'm totally messed. any help would be awesome.

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Sounds to me like your having a air leak... my hose on my tahoe had a tiny pin leak in it and it did the same thing... check the small hose that goes from the air filter to the head of the motor... that was where mine was if not, check your o2 censor...

Posted on Aug 09, 2008

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Keep in mind, I am not making fun of you, I have made my share of misspelled words and sentances which were a little confusing.
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0996b43f80203328.jpg enlarge_icon.gifenlarge_tooltip.gif Fig. Component Location Chart-2000 MPV

1 PCM 2 Mass air flow (MAF)/intake air temperature (IAT) sensor 3 Throttle position (TP) sensor 4 Fuel tank pressure sensor 5 Engine coolant temperature (ECT) sensor 6 Crankshaft position (CKP) sensor 7 Camshaft position (CMP) sensor 8 Knock sensor 9 Heated oxygen sensor (HO2S) (front, LH) 10 Heated oxygen sensor (HO2S) (front, RH) 11 Heated oxygen sensor (HO2S) (rear, LH) 12 Heated oxygen sensor (HO2S) (rear, RH) 13 EGR boost sensor 14 Power steering pressure (PSP) switch 15 Main relay


0996b43f8020330c.jpg enlarge_icon.gifenlarge_tooltip.gif Fig. Component Location Chart-2001 MPV

1 PCM 2 Mass air flow (MAF)/Intake air temperature (IAT) sensor 3 Throttle position (TP) sensor 4 Engine coolant temperature (ECT) sensor 5 Crankshaft position (CKP) sensor 6 Camshaft position (CMP) sensor 7 Knock sensor 8 Heated oxygen sensor (HO2S) (front, LH) 9 Heated oxygen sensor (HO2S) (front, RH) 10 Heated oxygen sensor (HO2S) (rear, LH)* 11 Heated oxygen sensor (HO2S) (rear, RH)* 12 EGR boost sensor


0996b43f8020330f.jpg enlarge_icon.gifenlarge_tooltip.gif Fig. Component Location Chart- 2002-06 MPV

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Figure 1: Fast Idle Control (FIC) Solenoid
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Throttle Body (TB) The throttle body (TB) controls the amount of air that flows into the engine through a single butterfly valve. The single butterfly valve opening is determined by the accelerator pedal. The TB is cast with an air bypass channel and houses several emission-related components for the powertrain control module (PCM).
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Throttle Position Sensor (TP Sensor) The throttle position (TP) sensor responds to the accelerator pedal movement. The TP sensor is a potentiometer that transforms the throttle plate opening angle into output voltage and sends the voltage signal to the powertrain control module (PCM). In addition, the sensor detects the opening and closing speed of the throttle plate and sends the voltage signal to the PCM. Also, the TP sensor is used to determine the air intake when the mass air flow (MAF) sensor fails. This mode of operation is called Fail Safe.
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IDLE SPEED

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Cutting out


Its more than likely a vacuum leak, basically air is entering the charge system that hasn't been metered by the Mass Air Flow Sensor.

What you can do is take a can of WD-40 and lightly spray your intake plumbing from Filter to Engine and see if the idle RPM changes. Don't spray directly onto the surface close enough that the liquid collects, just mist it from about 1 to 1-1/2 feet away slowly to see if you can pinpoint the location where the air is entering the intake system and then tighten up the connections if its at a joint, or replace your parts if there is a hole, for instance in a rubber piece.

I don't know how modified your car is, but if you have other supporting modifications to your car, but if you maxed out your stock Throttle Body (Which is highly unlikely if thats the only thing you've done to your car), you probably need to upgrade your ECU and possibly your Camshaft.

Also, if I may make a suggestion to you about your modifications to your car. If you've done all of this intake work, with no other supporting mods. You aren't going to get very far as far as Horsepower, Throttle Response, or Torque. You only need to upgrade how easily the air can get into the engine if you start getting into some Head-work, some light-bottom end work, and a very good exhaust. The most you'll see out of these modifications is 10-15 peak horsepower, and you probably actually lost some throttle response. I recommend you put the car back to stock and start upgrading the engine from the other end starting with the exhaust. A set of headers, a free-flow true-dual exhaust and a mild camshaft will do absolute wonders for Horsepower, Throttle Response, and Torque-band, not to mention if you do all these things, at that point you could start adding some intake upgrades.

I hope I didn't offend ya by this post, I'm just truly trying to help ya man from a hardcore gear head. Hehe

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